Spring MVC Beginner’s Guide Beginner's Amuthan G

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SpringMVCBeginner’sGuide
TableofContents
SpringMVCBeginner’sGuide
Credits
AbouttheAuthor
AbouttheReviewers
www.PacktPub.com
Supportfiles,eBooks,discountoffers,andmore
Whysubscribe?
FreeaccessforPacktaccountholders
Preface
Whatthisbookcovers
Whatyouneedforthisbook
Whothisbookisfor
Conventions
Timeforaction–heading
Whatjusthappened?
Popquiz–heading
Haveagohero–heading
Readerfeedback
Customersupport
Downloadingtheexamplecode
Errata
Piracy
Questions
1.ConfiguringaSpringDevelopmentEnvironment
SettingupJava
Timeforaction–installingJDK
Timeforaction–settingupenvironmentvariables
Configuringabuildtool
Timeforaction–installingtheMavenbuildtool
Installingawebserver
Timeforaction–installingtheTomcatwebserver
Configuringadevelopmentenvironment
Timeforaction–installingSpringToolSuite
Timeforaction–configuringTomcatonSTS
Whatjusthappened?
Timeforaction–configuringMavenonSTS
CreatingourfirstSpringMVCproject
Timeforaction–creatingaSpringMVCprojectinSTS
Whatjusthappened?
SpringMVCdependencies
Timeforaction–addingSpringjarstotheproject
Whatjusthappened?
Timeforaction–addingJavaversionpropertiesinpom.xml
Ajump-starttoMVC
Timeforaction–addingawelcomepage
Whatjusthappened?
Thedispatcherservlet
Timeforaction–configuringthedispatcherservlet
Whatjusthappened?
Deployingourproject
Timeforaction–runningtheproject
Summary
2.SpringMVCArchitecture–ArchitectingYourWebStore
Thedispatcherservlet
Timeforaction–examiningrequestmapping
Whatjusthappened?
Popquiz–requestmapping
Thewebapplicationcontext
Timeforaction–understandingthewebapplicationcontext
Whatjusthappened?
Popquiz–thewebapplicationcontext
Thewebapplicationcontextconfiguration
Popquiz–webapplicationcontextconfiguration
Viewresolvers
Timeforaction–understandingInternalResourceViewResolver
Whatjusthappened?
ModelViewController
AnoverviewoftheSpringMVCrequestflow
Thewebapplicationarchitecture
Thedomainlayer
Timeforaction–creatingadomainobject
Whatjusthappened?
Thepersistencelayer
Timeforaction–creatingarepositoryobject
Whatjusthappened?
Theservicelayer
Timeforaction–creatingaserviceobject
Whatjusthappened?
Haveagohero–accessingtheproductdomainobjectviaaservice
Anoverviewofthewebapplicationarchitecture
Haveagohero–listingallourcustomers
Summary
3.ControlYourStorewithControllers
Definingacontroller
Timeforaction–addingclass-levelrequestmapping
Whatjusthappened?
Popquiz–class-levelrequestmapping
TheroleofacontrollerinSpringMVC
Handlermapping
UsingURItemplatepatterns
Timeforaction–showingproductsbasedoncategory
Whatjusthappened?
Popquiz–requestpathvariable
Usingmatrixvariables
Timeforaction–showingtheproductsbasedonfilter
Whatjusthappened?
Understandingrequestparameters
Timeforaction–addingtheproductdetailspage
Whatjusthappened?
Popquiz–therequestparameter
Timeforaction–implementingamasterdetailview
Whatjusthappened?
Haveagohero–addingmultiplefilterstolistproducts
Summary
4.WorkingwithSpringTagLibraries
Servingandprocessingforms
Timeforaction–servingandprocessingforms
Whatjusthappened?
Customizingdatabinding
Timeforaction–whitelistingformfields
Whatjusthappened?
Externalizingtextmessages
Timeforaction–externalizingmessages
Whatjusthappened?
UsingSpringSecuritytags
Timeforaction–addingaloginpage
Whatjusthappened?
Summary
5.WorkingwithViewResolver
Resolvingviews
Theredirectview
Timeforaction–examiningRedirectView
Whatjusthappened?
Popquiz–redirectview
Servingstaticresources
Timeforaction–servingstaticresources
Whatjusthappened?
Popquiz–staticview
Timeforaction–addingimagestotheproductdetailpage
Whatjusthappened?
Themultipartrequestinaction
Timeforaction–addingimagestotheproductpage
Whatjusthappened?
Haveagohero–uploadingproductusermanualstotheserver
UsingContentNegotiatingViewResolver
Timeforaction–configuringContentNegotiatingViewResolver
Whatjusthappened?
Workingwiththehandlerexceptionresolver
Timeforaction–addingtheresponsestatusexception
Whatjusthappened?
Timeforaction–addinganexceptionhandler
Whatjusthappened?
Summary
6.InterceptYourStorewithInterceptor
Workingwithinterceptors
Timeforaction–configuringaninterceptor
Whatjusthappened?
Popquiz–interceptor
Internationalization(i18n)
Timeforaction–addinginternationalization
Whatjusthappened?
Haveagohero–fullyinternationalizetheproductdetailpage
Auditlogging
Timeforaction–addingthedataauditinterceptor
Whatjusthappened?
Conditionalredirecting
Timeforaction–interceptingofferpagerequests
Whatjusthappened?
Summary
7.ValidateYourProductswithaValidator
Beanvalidation
Timeforaction–addingbeanvalidationsupport
Whatjusthappened?
Haveagohero–addingmorevalidationintheaddproductspage
CustomvalidationwithJSR-303/beanvalidation
Timeforaction–addingcustomvalidationsupport
Whatjusthappened?
Haveagohero–addingcustomvalidationtoacategory
Springvalidation
Timeforaction–addingSpringvalidation
Whatjusthappened?
Timeforaction–combiningSpringandbeanvalidations
Whatjusthappened?
Haveagohero–addingSpringvalidationtotheproductimage
Summary
8.GiveRESTtoYourApplicationwithAjax
IntroducingREST
Timeforaction–implementingRESTfulwebservices
Whatjusthappened?
Timeforaction–consumingRESTwebservices
Whatjusthappened?
HandlingawebserviceinAjax
Timeforaction–consumingRESTwebservicesviaAjax
Whatjusthappened?
Summary
9.ApacheTilesandSpringWebFlowinAction
WorkingwithSpringWebFlow
Timeforaction–implementingtheorder-processingservice
Whatjusthappened?
Timeforaction–implementingthecheckoutflow
Whatjusthappened?
Understandingtheflowdefinition
Understandingthecheckoutflow
Popquiz–webflow
Timeforaction–creatingviewsforeveryviewstate
Whatjusthappened?
Haveagohero–addingadecisionstate
EnhancingreusabilitythroughApacheTiles
Timeforaction–creatingviewsforeveryviewstate
Whatjusthappened?
Popquiz–ApacheTiles
Summary
10.TestingYourApplication
Unittesting
Timeforaction–unit-testingdomainobjects
Whatjusthappened?
Haveagohero–addingtestsforcart
IntegrationtestingwiththeSpringTestContextframework
Timeforaction–testingtheproductvalidator
Whatjusthappened?
Timeforaction–testingtheproductcontroller
Whatjusthappened?
Timeforaction–testingRESTcontrollers
Whatjusthappened?
Haveagohero–addingtestsfortheremainingRESTmethods
Summary
A.UsingtheGradleBuildTool
InstallingGradle
TheGradlebuildscriptforyourproject
UnderstandingtheGradlescript
B.PopQuizAnswers
Chapter2,SpringMVCArchitecture–ArchitectingYourWebStore
Popquiz–requestmapping
Popquiz–thewebapplicationcontext
Popquiz–webapplicationcontextconfiguration
Chapter3,ControlYourStorewithControllers
Popquiz–class-levelrequestmapping
Popquiz–requestpathvariable
Popquiz–therequestparameter
Chapter5,WorkingwithViewResolver
Popquiz–redirectview
Popquiz–staticview
Chapter6,InterceptYourStorewithInterceptor
Popquiz–interceptor
Chapter9,ApacheTilesandSpringWebFlowinAction
Popquiz–webflow
Popquiz–ApacheTiles
Index
SpringMVCBeginner’sGuide
SpringMVCBeginner’sGuide
Copyright©2014PacktPublishing
Allrightsreserved.Nopartofthisbookmaybereproduced,storedinaretrievalsystem,
ortransmittedinanyformorbyanymeans,withoutthepriorwrittenpermissionofthe
publisher,exceptinthecaseofbriefquotationsembeddedincriticalarticlesorreviews.
Everyefforthasbeenmadeinthepreparationofthisbooktoensuretheaccuracyofthe
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warranty,eitherexpressorimplied.Neithertheauthor,norPacktPublishing,andits
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Firstpublished:June2014
Productionreference:1190614
PublishedbyPacktPublishingLtd.
LiveryPlace
35LiveryStreet
BirminghamB32PB,UK.
ISBN978-1-78328-487-0
www.packtpub.com
CoverimagebyAniketSawant(<aniket_sawant_photography@hotmail.com>)
Credits
Author
AmuthanG
Reviewers
RafałBorowiec
PawanChopra
RubénClementeSerna
AcquisitionEditor
VinayArgekar
ContentDevelopmentEditor
AzharuddinSheikh
TechnicalEditors
MonicaJohn
NehaMankare
ShinyPoojary
CopyEditors
GladsonMonteiro
InsiyaMorbiwala
AdityaNair
StutiSrivastava
ProjectCoordinators
KinjalBari
WendellPalmer
Proofreaders
SimranBhogal
StephenCopestake
MariaGould
AmeeshaGreen
PaulHindle
Indexer
HemanginiBari
Graphics
DishaHaria
AbhinashSahu
ProductionCoordinator
AparnaBhagat
CoverWork
AparnaBhagat
AbouttheAuthor
AmuthanGhasoversixyearsofexperienceasaprofessionalsoftwaredeveloper.He
currentlyworksforalargecloudplatformcompanyandhasstrongproductdevelopment
experienceinJava,Spring,JPA,andmanyotherenterprisetechnologies.Inhisfreetime,
heenjoysbloggingonhissite(http://www.madebycode.in).Hecanbecontactedat
<mr.amuthan@gmail.com>.
IwouldliketogratefullyandsincerelythankMr.VincentKokforhisguidance,
understanding,patience,andmostimportantly,hisfriendshipduringmyfirstjobat
EducatorInc.Hismentorshiphasshapedmetobecomeawell-roundedprofessional.He
encouragedmetonotonlygrowasadeveloper,butalsoasanindependentthinker.
IwanttotakeamomentandexpressmygratitudetotheentireteamatPacktPublishing
fortheirpatienceandcooperation.WhenIsignedupforthisbook,Ireallyhadnoidea
howthingswouldturnout.Icouldn’thavepulledthisoffwithouttheirguidance.
Iwouldliketoexpressmygratitudetoallmyfriendsandfamilyforprovidingmewith
unendingencouragementandsupport.Ioweeverychallengeandaccomplishmenttoall
mylovelycolleagueswhotaughtmealotovertheyears.
AspecialthankstoDivyaandArunfortheirencouragement,friendship,andsupport.
Theywereastrongshouldertoleanoninthemostdifficulttimesduringthewritingof
thisbook.
Finally,andmostimportantly,IwouldliketothankmywifeManjuwhobelievesmemore
thanmyself.Hersupport,encouragement,quietpatience,andunwaveringlovewere
undeniablythebedrockuponwhichmylifehasbeenbuilt.
AbouttheReviewers
RafałBorowiecisanITspecialistwithabouteightyearsofcommercialexperience,
specializinginsoftwaretestingandqualityassurance,softwaredevelopment,project
management,andteamleadership.
HecurrentlyholdsthepositionofaTeamLeaderatGoyello,whereheismainly
responsibleforbuildingandmanagingteamsofprofessionaldevelopersandtesters.Heis
alsoresponsibleformaintainingrelationswithcustomersandacquiringnewones,mainly
throughconsultancy.
Hebelievesinagileprojectmanagementandisabigfanoftechnology,especially
technologythatisJavarelated(butnotlimitedtoit).Helikessharingknowledgeabout
softwaredevelopmentandpracticesthroughhisblog(blog.codeleak.pl)andTwitter
account(@kolorobot)andalsoatinternalandexternaleventssuchasconferencesor
workshops.
PawanChopraisanAgiledeveloperwitheightyearsofexperienceinthesoftware
industry.HecurrentlyworksatWebners(http://www.webnersolutions.com/)onsomecool
JavaScript,Java,HTML5,Node,andAngularJSprojects.Heisanopensourceenthusiast.
Helovessharingknowledgethroughtrainingandblogging.Heisalsoverystrongonthe
serversidewithvastexperienceinSpringandHibernatetools.Heblogsat
www.itspawan.com.
RubénClementeSernaisasoftwareengineerbyprofessionwithovereightyearsof
experienceinsoftwaredevelopment.HerecentlymovedtotheUKandiscurrently
workingasaJavaDeveloperatPiksel,acompanythatcreatesandmanagesOTTvideo
solutionsforsomeoftheworld’sleadingmediabrands.PriortoPiksel,hehasworkedat
GFIInformáticainSpainonmanyJavadevelopmentprojects,mainlyfortelecomand
governmentservicecustomers.
Moredetailedinformationabouthisskillsandexperiencecanbefoundat
http://www.linkedin.com/in/rubenclementeserna.Hecanbecontactedat
<rubenclemente@gmail.com>.
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Preface
Thisbookhasaveryclearaim:tointroduceyoutotheincrediblesimplicityandpowerof
SpringMVC.IstillrememberfirstlearningabouttheSpringframeworkbackin2009.
Thebestwaytotestwhetherornotyoureallyunderstandaconceptistotrytoteachitto
someoneelse.Inmycase,IhavetaughtSpringMVCtoMVC;areyouconfused?Imean
thatbackin2009,ItaughtittomywifeManjuViswambaranChandrika(MVC).During
thatcourse,Iwasabletounderstandthekindofdoubtsthatariseinabeginner’smind.I
havegatheredallmyteachingknowledgeandputitinthisbookinanelegantwaysothat
itcanbeunderstoodwithoutconfusion.
Thisbookfollowsathemeofdevelopingasimplee-commercesitestep-by-step.Inevery
successivechapter,youwilllearnanewconceptofSpringMVC.Obviously,theaimisto
teachyouhowyoucanuseSpringMVCeffectively.Developingafull-blown,production-
readye-commercesiteisnotthepurposeofthisbook.
Whatthisbookcovers
Chapter1,ConfiguringaSpringDevelopmentEnvironment,willgiveyouaquick
overviewofSpringMVCanditsarchitectureandguideyouthroughdetailednotesand
step-by-stepinstructionstosetupyourdevelopmentenvironment.Afterinstallingthe
requiredprerequisites,youwilltryoutaquickexampleofhowtodevelopanapplication
withSpringMVC.Althoughthechapterdoesn’texplainallthecodeindetail,you’llpick
upafewthingsintuitively.
Chapter2,SpringMVCArchitecture–ArchitectingYourWebStore,willlaydownthe
groundworkforthesampleapplicationthatwearegoingtobuildalongtheway,chapter
bychapter.Thischapterwillintroduceyoutoconceptssuchasrequestmapping,web
applicationcontext,SpringMVCrequestflow,andthelayeredarchitectureofatypical
webapplication.
Chapter3,ControlYourStorewithControllers,willtakeyouthroughtheconceptofa
controller;youwilllearnmoreabouthowtodefineacontroller,anduseURItemplate
patterns,matrixvariables,andrequestparameters.
Chapter4,WorkingwithSpringTagLibraries,willteachyouhowtouseSpringand
Springformtaglibrariesinwebformhandling.Youwilllearnhowtobinddomainobjects
withviewsandhowtousemessagebundlestoexternalizelabelcaptiontexts.Attheend
ofthischapter,youwillseehowtoaddaloginform.
Chapter5,WorkingwithViewResolver,willpresenttheinnermechanicsofhow
InternalResourceViewResolverresolvesaviewandtakesyouthroughhowtouse
variousviewtypes,suchasredirectviewandstaticview.Youwillalsolearnaboutthe
multipartresolverandcontentnegotiationviewresolver.Finally,youwilllearnhowtouse
exceptionhandlerresolvers.
Chapter6,InterceptYourStorewithInterceptor,willpresenttheconceptofaninterceptor
toyou.Youwilllearnhowtoleveragetheinterceptortohandleortransformrequestsand
responsesflexibly.Thischapterwillteachyouhowtomakeyourwebpagesupport
internalizationwiththehelpofLocaleChangeInterceptor.Thischapteralsointroduces
howtoperformauditlogginginalogfileusingtheinterceptorconcept.
Chapter7,ValidateYourProductswithaValidator,willgiveyouanoverviewofthe
validationconcept.Youwilllearnaboutbeanvalidation,andyouwilllearnhowto
performcustomvalidationalongwiththestandardbeanvalidation.Youwillalsolearn
abouttheclassicSpringvalidationandhowtocombineitwithbeanvalidation.
Chapter8,GiveRESTtoYourApplicationwithAjax,willteachyouthebasicprinciplesof
RESTandAjax.YouwilllearnhowtodevelopanapplicationinRESTfulservices.The
basicconceptofHTTPverbsandhowtheyarerelatedtostandardCRUDoperationswill
beexplained,andyouwilllearnhowtofireanAjaxrequestandhandleitfromaweb
page.
Chapter9,ApacheTilesandSpringWebFlowinAction,willteachyouhowtousethe
Springwebflowtodevelopworkflow-basedwebpages.Youwilllearnmoreaboutstates
andtransitionsinwebflowandhowtodefineaflowdefinition.Thischapteralsoteaches
youhowtodecomposeapageusingApachetiles.Youwillalsolearnmoreabout
TileViewResolverandhowtodefinereusableApachetilestemplates.
Chapter10,TestingyourApplication,willteachyouhowtoleveragetheSpringtesting
capabilitytotestyourcontrollers.Youwilllearnhowtoloadthetestcontextandhowto
mocktheserviceandrepositorylayers.ThischapteralsointroducesyoutotheSpring
MVCtestmoduleandteachesyouhowtousethat.
AppendixA,UsingtheGradleBuildTool,introducesyoutousingtheGradlebuildtool
foroursampleapplication.YouwilllearnabouttheGradlescriptthatisrequiredtobuild
ourprojectusingGradlebuildtool.
Whatyouneedforthisbook
Toruntheexamplesinthebook,thefollowingsoftwarewillberequired:
JavaSEDevelopmentKit7u45ornewer
Maven3.1.0
ApacheTomcat7.0
STS3.4.0release(SpringToolSuite)
Whothisbookisfor
Thisbookisdesignedtobefollowedfrombeginningtoend,althoughthosewithexisting
knowledgeofSpringMVCwillbeabletojumpintothelaterchaptersandpickoutthings
thatareimportanttothem.YouarenotexpectedtobeexperiencedwiththeSpring
framework.Someknowledgeofservletprogramminganddependencyinjectionwillbe
helpfulbutnotessential.Inanutshell,thebookprovidesclearpictures,illustrations,
concepts,andisideallysuitedforbeginnersandintermediatedevelopers.
Conventions
Inthisbook,youwillfindseveralheadingsappearingfrequently.
Togiveclearinstructionsofhowtocompleteaprocedureortask,weuse:
Timeforaction–heading
1. Action1
2. Action2
3. Action3
Instructionsoftenneedsomeextraexplanationsothattheymakesense,sotheyare
followedwith:
Whatjusthappened?
Thisheadingexplainstheworkingoftasksorinstructionsthatyouhavejustcompleted.
Youwillalsofindsomeotherlearningaidsinthebook,including:
Popquiz–heading
Theseareshortmultiple-choicequestionsintendedtohelpyoutestyourown
understanding.
Haveagohero–heading
Thesepracticalchallengesgiveyouideasforexperimentingwithwhatyouhavelearned.
Youwillalsofindanumberofstylesoftextthatdistinguishbetweendifferentkindsof
information.Herearesomeexamplesofthesestylesandanexplanationoftheirmeaning.
Codewordsintext,databasetablenames,foldernames,filenames,fileextensions,
pathnames,dummyURLs,userinput,andTwitterhandlesareshownasfollows:“Once
thedownloadisfinished,gotothedownloadeddirectoryandextractthe.zipfileintoa
convenientdirectoryofyourchoice.”
Ablockofcodeissetasfollows:
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1>${greeting}</h1>
<p>${tagline}</p>
</div>
</div>
</section>
</body>
Whenwewishtodrawyourattentiontoaparticularpartofacodeblock,therelevant
linesoritemsaresetinbold:
<servlet>
<servlet-name>DefaultServlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet
</servlet-class>
</servlet>
Anycommand-lineinputoroutputiswrittenasfollows:
C:\>mvn-version
ApacheMaven3.2.1(ea8b2b07643dbb1b84b6d16e1f08391b666bc1e9;2014-02-
14T12:37:52-05:00)
Mavenhome:C:\ProgramFiles\apache-maven-3.2.1
Javaversion:1.7.0_51,vendor:OracleCorporation
Javahome:C:\ProgramFiles\Java\jdk1.7.0_51\jre
Defaultlocale:en_SG,platformencoding:Cp1252
OSname:"windows7",version:"6.1",arch:"amd64",family:"windows"
Newtermsandimportantwordsareshowninbold.Wordsthatyouseeonthescreen,in
menusordialogboxesforexample,appearinthetextlikethis:“ASystemProperties
windowwillappear;inthiswindow,selecttheAdvancedtabandclickonthe
EnvironmentVariablesbuttontoopentheenvironmentvariableswindow.”
Note
Warningsorimportantnotesappearinaboxlikethis.
Tip
Tipsandtricksappearlikethis.
Readerfeedback
Feedbackfromourreadersisalwayswelcome.Letusknowwhatyouthinkaboutthis
book—whatyoulikedormayhavedisliked.Readerfeedbackisimportantforusto
developtitlesthatyoureallygetthemostoutof.
Tosendusgeneralfeedback,simplysendane-mailto<feedback@packtpub.com>,and
mentionthebooktitlethroughthesubjectofyourmessage.
Ifthereisatopicthatyouhaveexpertiseinandyouareinterestedineitherwritingor
contributingtoabook,seeourauthorguideonwww.packtpub.com/authors.
Customersupport
NowthatyouaretheproudownerofaPacktbook,wehaveanumberofthingstohelp
youtogetthemostfromyourpurchase.
Downloadingtheexamplecode
YoucandownloadtheexamplecodefilesforallPacktbooksyouhavepurchasedfrom
youraccountathttp://www.packtpub.com.Ifyoupurchasedthisbookelsewhere,youcan
visithttp://www.packtpub.com/supportandregistertohavethefilese-maileddirectlyto
you.
Errata
Althoughwehavetakeneverycaretoensuretheaccuracyofourcontent,mistakesdo
happen.Ifyoufindamistakeinoneofourbooks—maybeamistakeinthetextorthe
code—wewouldbegratefulifyouwouldreportthistous.Bydoingso,youcansave
otherreadersfromfrustrationandhelpusimprovesubsequentversionsofthisbook.If
youfindanyerrata,pleasereportthembyvisitinghttp://www.packtpub.com/submit-
errata,selectingyourbook,clickingontheerratasubmissionformlink,andenteringthe
detailsofyourerrata.Onceyourerrataareverified,yoursubmissionwillbeacceptedand
theerratawillbeuploadedtoourwebsite,oraddedtoanylistofexistingerrata,underthe
Erratasectionofthattitle.
Piracy
PiracyofcopyrightmaterialontheInternetisanongoingproblemacrossallmedia.At
Packt,wetaketheprotectionofourcopyrightandlicensesveryseriously.Ifyoucome
acrossanyillegalcopiesofourworks,inanyform,ontheInternet,pleaseprovideuswith
thelocationaddressorwebsitenameimmediatelysothatwecanpursuearemedy.
Pleasecontactusat<copyright@packtpub.com>withalinktothesuspectedpirated
material.
Weappreciateyourhelpinprotectingourauthors,andourabilitytobringyouvaluable
content.
Questions
Youcancontactusat<questions@packtpub.com>ifyouarehavingaproblemwithany
aspectofthebook,andwewilldoourbesttoaddressit.
Chapter1.ConfiguringaSpring
DevelopmentEnvironment
Inthischapter,wearegoingtakealookathowwecancreateabasicSpringMVC
application.InordertodevelopaSpringMVCapplication,weneedsomeprerequisite
softwareandtools.First,wearegoingtolearnhowtoinstallalltheprerequisitesthatare
requiredtosetupourdevelopmentenvironmentsothatwecanstartdevelopingthe
application.
ThesetupandinstallationstepsgivenhereareforWindowsoperatingsystems,butdon’t
worry,asthestepsmaychangeonlyslightlyforotheroperatingsystems.Youcanalways
refertotherespectivetools/softwarevendor’swebsitestoinstalltheminotheroperating
systems.Inthischapter,wewilllearnhowtosetupJavaandconfiguretheMavenbuild
tool,installtheTomcatwebserver,installandconfiguretheSpringtoolsuite,andcreate
andrunourfirstSpringMVCproject.
SettingupJava
Obviously,thefirstthingthatweneedtodoisgetstartedwithJava.Themoretechnical
nameforJavaisJavaDevelopmentKit(JDK).JDKincludesaJavacompiler(javac),a
Javavirtualmachine,andavarietyofothertoolstocompileandrunJavaprograms.
Timeforaction–installingJDK
WearegoingtouseJava7butJava6oranyhigherversionisalsosufficient.Let’stakea
lookathowwecaninstallJDKonWindowsoperatingsystems:
1. GototheJavaSEdownloadpageontheOraclewebsitebyenteringthefollowing
URLinyourbrowser:
http://www.oracle.com/technetwork/java/javase/downloads/index.html.
2. ClickontheJavaplatformJDK7downloadlink;thiswilltakeyoutothelicense
agreementpage.Acceptthelicenseagreementbyselectingthatoptioninradio
button.
3. Now,clickonthelisteddownloadlinkthatcorrespondstoyourWindowsoperating
systemarchitecture;forinstance,ifyouroperatingsystemisoftype32bit,clickon
thedownloadlinkthatcorrespondstoWindowsx86.Or,ifyouroperatingsystemis
oftype64bit,clickonthedownloadlinkthatcorrespondstoWindowsx64.
4. Now,itwillstartdownloadingtheinstaller.Oncethedownloadisfinished,gotothe
downloadeddirectoryanddouble-clickontheinstaller.Thiswillopenupthe
followingwizardwindow;justclickontheNextbuttoninthewizard,leavingthe
defaultoptionsalone,andclickontheClosebuttonattheendofthewizard:
JDKinstallationwizard
Tip
Additionally,aseparatewizardalsopromptsyoutoinstallJavaRuntime
Environment(JRE).GothroughthatwizardaswelltoinstallJREinyoursystem.
5. NowyoucanseetheinstalledJDKdirectoryinthedefaultlocation;inourcase,the
defaultlocationisC:\ProgramFiles\Java\jdk1.7.0_25.
Timeforaction–settingupenvironment
variables
AfterinstallingJDK,westillneedtoperformsomemoreconfigurationstouseJava
convenientlyfromanydirectoryonourcomputer.Bysettinguptheenvironmentvariables
forJavaintheWindowsoperatingsystem,wecanmaketheJavacompilerandtools
availabletotheentireoperatingsystem:
1. NavigatetoControlPanel|System|Advancedsystemsettings.
2. ASystemPropertieswindowwillappear;inthiswindow,selecttheAdvancedtab
andclickontheEnvironmentVariablesbuttontoopentheenvironmentvariables
window.
3. Now,clickontheNewbuttonintheSystemvariablespanel,enterJAVA_HOMEasthe
variablename,andentertheinstalledJDKdirectorypathasthevariablevalue;inour
case,thisisC:\ProgramFiles\Java\jdk1.7.0_51.Incaseyoudonothaveproper
rightsfortheoperatingsystem,youwillnotbeabletoeditSystemvariables;inthat
case,youcancreatetheJAVA_HOMEvariableundertheUservariablespanel.
4. Now,inthesameSystemvariablespanel,double-clickonthePATHvariableentry;
anEditSystemVariablewindowwillappear.
SettingPATHEnvironmentvariable
5. EditVariablevalueofPathbyappendingthe;%JAVA_HOME%\bintexttoitsexisting
value.
Tip
Editthepathvariablecarefully;youshouldonlyappendthetextattheendofexisting
value.Don’tdeleteordisturbtheexistingvalues;makesureyouhaven’tmissedthe;
(semicolon)markasthatisthefirstletterinthetextthatyouwillappend.
6. NowclickontheOKbutton.
NowwehaveinstalledJavainourcomputer.Toverifywhetherourinstallationhasbeen
carriedoutcorrectly,openanewcommandwindowandtypejava–versionandpress
Enter;youwillseetheinstalledversionofJavaonthescreen:
C:\>java-version
javaversion"1.7.0_51"
Java(TM)SERuntimeEnvironment(build1.7.0_51-b13)
JavaHotSpot(TM)64-BitServerVM(build24.51-b03,mixedmode)
Configuringabuildtool
Buildingasoftwareprojecttypicallyincludessomeactivitiessuchasthefollowing:
Compilingallthesourcecode
Generatingthedocumentationfromthesourcecode
PackagingthecompiledcodeintoaJARorWARarchivefile
Installingthepackagedarchivesfilesonaserver
Manuallyperformingallthesetasksistimeconsumingandispronetoerrors.Therefore,
wetakethehelpofabuildtool.Abuildtoolisatoolthatautomateseverythingrelatedto
buildingasoftwareproject,fromcompilingtodeploying.
Timeforaction–installingtheMaven
buildtool
ManybuildtoolsareavailableforbuildingaJavaproject.WearegoingtouseMaven
3.2.1asourbuildtool.Let’stakealookathowwecaninstallMaven:
1. GotoMaven’sdownloadpagebyenteringthefollowingURLonyourbrowser:
http://maven.apache.org/download.cgi
2. Clickontheapache-maven-3.2.1-bin.zipdownloadlink,andstartthedownload.
3. Oncethedownloadisfinished,gotothedownloadeddirectoryandextractthe.zip
fileintoaconvenientdirectoryofyourchoice.
4. Nowweneedtocreateonemoreenvironmentvariable,calledM2_HOME,inawaythat
issimilartothewayinwhichwecreatedJAVA_HOME.EntertheextractedMavenzip
directory’spathasthevaluefortheM2_HOMEenvironmentvariable.
5. Createonemoreenvironmentvariable,calledM2,withthevalue%M2_HOME%\bin,as
showninthefollowingscreenshot:
SettingtheM2environmentvariable
6. FinallyappendtheM2variabletothePATHenvironmentvariableaswellbysimply
appendingthe;%M2%texttothePATHvariable’svalue.
NowwehaveinstalledtheMavenbuildtoolinourcomputer.Toverifywhetherour
installationhasbeencarriedoutcorrectly,weneedtofollowstepsthataresimilartothe
Javainstallationverification.Openanewcommandwindow,typemvn–version,and
pressEnter;youwillseethefollowingdetailsoftheMavenversion:
C:\>mvn-version
ApacheMaven3.2.1(ea8b2b07643dbb1b84b6d16e1f08391b666bc1e9;2014-02-
14T12:37:52-05:00)
Mavenhome:C:\ProgramFiles\apache-maven-3.2.1
Javaversion:1.7.0_51,vendor:OracleCorporation
Javahome:C:\ProgramFiles\Java\jdk1.7.0_51\jre
Defaultlocale:en_SG,platformencoding:Cp1252
OSname:"windows7",version:"6.1",arch:"amd64",family:"windows"
Installingawebserver
Sofar,wehavelearnedhowtoinstallJDKandMaven.Usingthesetools,wecancompile
theJavasourcecodeintothe.classfilesandpackagethese.classfilesintothe.jaror
.wararchives.However,howdowerunourpackagedarchives?Todothis,wetakethe
helpofawebserver;awebserverwillhostourpackagedarchivesasarunning
application.
Timeforaction–installingtheTomcat
webserver
ApacheTomcatisapopularJavawebservercumservletcontainer.Wearegoinguse
ApacheTomcatVersion7.0.Let’stakealookathowwecaninstalltheTomcatweb
server:
1. GototheApacheTomcathomepageusingthefollowingURLlink:
http://tomcat.apache.org/
2. ClickontheTomcat7.0downloadlink,anditwilltakeyoutothedownloadpage.
3. Clickonthe32-bit/64-bitWindowsServiceInstallerlink;itwillstartdownloading
theinstaller.
4. Oncethedownloadisfinished,gotothedownloadeddirectoryanddouble-clickon
theinstaller;thiswillopenupawizardwindow.
5. Justclickthroughthenextbuttonsinthewizard,leavingthedefaultoptionsalone,
andclickontheFinishbuttonattheendofthewizard.Notethatbeforeclickingon
theFinishbutton,justensurethatyouhaveuncheckedRunApacheTomcat
checkbox.
InstallingApacheTomcatwiththedefaultoptionworkssuccessfullyonlyifyouhave
installedJavainthedefaultlocation.Otherwise,youhavetocorrectlyprovidetheJRE
pathaccordingtothelocationofyourJavainstallationduringtheinstallationofTomcat,
asshowninthefollowingscreenshot:
TheJavaruntimeselectionfortheTomcatinstallation
Configuringadevelopmentenvironment
WeinstalledJavaandMaventocompileandpackageJavasourcecode,andweinstalled
Tomcattodeployandrunourapplication.However,priortoallthis,wehavetowritethe
SpringMVCcodesothatwecancompile,package,andrunthecode.
Wecanuseanysimpletexteditoronourcomputertowriteourcode,butthatwon’thelp
usmuchwithfeaturessuchasfindingsyntaxerrorsaswetype,autosuggestingimportant
keywords,syntaxhighlighting,easynavigation,andsoon.
IntegratedDevelopmentEnvironment(IDE)canhelpuswiththesefeaturestodevelop
thecodefasteranderrorfree.WearegoingtouseSpringToolSuite(STS)asourIDE.
Timeforaction–installingSpringTool
Suite
STSisthebestEclipse-powereddevelopmentenvironmenttobuildSpringapplications.
Let’stakealookathowwecaninstallSTS:
1. GototheSTSdownloadpageathttp://spring.io/tools/sts/all.
2. ClickontheSTSinstaller.exelinktodownloadthefilethatcorrespondstoyour
windowsoperatingsystemarchitecturetype(32bitor62bit);thiswillstartthe
downloadoftheinstaller.TheSTSstablereleaseversionatthetimeofwritingthis
bookisSTS3.4.0.RELEASEbasedonEclipse4.3.1.
3. Oncethedownloadisfinished,gotothedownloadeddirectoryanddouble-clickon
theinstaller;thiswillopenupawizardwindow.
4. Justclickthroughthenextbuttonsinthewizard,leavingthedefaultoptionsalone;if
youwanttocustomizetheinstallationdirectory,youcanspecifythatinthestepsyou
performinthewizard.
Tip
Downloadingtheexamplecode
YoucandownloadtheexamplecodefilesforallPacktbooksyouhavepurchased
fromyouraccountathttp://www.packtpub.com.Ifyoupurchasedthisbook
elsewhere,youcanvisithttp://www.packtpub.com/supportandregistertohavethe
filese-maileddirectlytoyou.
5. Instep5ofthewizard,youhavetoprovidetheJDKpath;justentertheJDKpath
thatyouconfiguredfortheJAVA_HOMEenvironmentvariable,asshowninthe
followingscreenshot:
SettingtheJDKpathduringtheSTSinstallation
WehavealmostinstalledallthetoolsandsoftwarerequiredtodevelopaSpringMVC
application,sonow,wecancreateourSpringMVCprojectonSTS.However,before
jumpingintocreatingaproject,weneedtoperformafinalconfigurationforSTS.
Timeforaction–configuringTomcaton
STS
AsIalreadymentioned,wecanusetheTomcatwebservertodeployourapplication,but
wehavetoinformSTSaboutthelocationoftheTomcatcontainersothatwecaneasily
deployourprojectfromSTStoTomcat.Let’sconfigureTomcatonSTS:
1. OpenSTSfromthestartmenuoptionorthedesktopicon.
2. STSwillaskyoutoprovideaworkspacedirectorylocation;provideaworkspace
directorypathasyouwishandclickontheOKbutton.
3. Now,STSwillshowyouawelcomescreen.Closethewelcomescreenandgotothe
menubarandnavigatetoWindow|preferences|Server|RuntimeEnvironments.
4. Youcanseetheavailableserverslistedontheright-handside;youmayalsosee
VMwarevFabrictcServerlistedundertheavailableservers,whichcomesalong
withtheSTSinstallation.
5. NowclickontheAddbuttontoaddourTomcatwebserver.
6. Awizardwindowwillappear;typetomcatintheSelectthetypeofruntime
environment:textbox,andalistofavailableTomcatversionswillbeshown.Just
selectTomcatv7.0andselecttheCreateanewlocalservercheckbox.Finally,click
ontheNextbutton,asshowninthefollowingscreenshot:
SelectingtheservertypeduringtheTomcatconfigurationonSTS
7. Inthenextwindow,clickontheBrowsebuttonandlocateTomcat’sinstalled
directory,andclickontheOKbutton.YoucanfindTomcat’sinstalleddirectory
underC:\ProgramFiles\ApacheSoftwareFoundation\Tomcat7.0ifyouhave
installedTomcatinthedefaultlocation.Then,clickontheFinishbutton,asshownin
thefollowingscreenshot:
SelectingtheTomcatlocationduringtheTomcatconfigurationonSTS
Whatjusthappened?
Instep2,weprovidedaworkspacepathforSTS.WhenyouopenSTSfortheveryfirst
timeafterinstallingSTS,itwillaskyoutoprovideaworkspacelocation.Thisisbecause
whenyoucreateaprojectonSTS,allyourprojectfileswillbecreatedunderthislocation
only.
OnceweenterSTS,weshouldinformSTSwheretheTomcathasbeeninstalled.Only
thencanSTSuseyourTomcatwebservertodeploytheproject.Thisisalsoaone-time
configuration;youneednotperformthisconfigurationeverytimeyouopenSTS.Wedid
thisbycreatinganewserverruntimeenvironmentinstep5.AlthoughSTSmightcome
withaninternalVMwarevFabrictcServer,wechosetousetheTomcatwebserveras
ourserverruntimeenvironment.
Timeforaction–configuringMavenon
STS
WelearnedhowtoconfigureTomcatonSTS.Similarly,tobuildourproject,STSwilluse
Maven.ButwehavetotellSTSwhereMavenhasbeeninstalledsothatitcanusethe
Maveninstallationtobuildourprojects.Let’stakealookathowwecanconfigureMaven
onSTS:
1. OpenSTSifitisnotalreadyopen.
2. NavigatetoWindow|Preferences|Maven|Installations.
3. Ontheright-handside,youcanseetheAddbutton,tolocateMaven’sinstallation.
4. ClickontheAddbuttonandchooseMaven’sinstalleddirectory,asshowninthe
followingscreenshot:
SelectingMaven’slocationduringtheMavenconfigurationonSTS
5. NowclickontheOKbuttoninthePreferenceswindowandcloseit.
CreatingourfirstSpringMVCproject
Sofar,wehavelearnedhowwecaninstallalltheprerequisitetoolsandsoftware.Nowwe
aregoingtodevelopourfirstSpringMVCapplicationusingSTS.STSprovidesaneasy-
to-useprojecttemplate.Usingthesetemplates,wecanquicklycreateourprojectdirectory
structureswithoutmanyproblems.
Timeforaction–creatingaSpringMVC
projectinSTS
Let’screateourfirstspringMVCprojectinSTS:
1. InSTS,navigatetoFile|New|Project;aNewProjectwizardwindowwillappear.
2. SelectMavenProjectfromthelistandclickontheNextbutton,asshowninthe
followingscreenshot:
Mavenproject’stemplateselection
3. Now,aNewMavenProjectdialogwindowwillappear;justselectthecheckboxthat
hastheCreateasimpleproject(skiparchetypeselection)caption,andclickonthe
Nextbutton.
4. Thewizardwillaskyoutospecifyartifact-relatedinformationforyourproject;just
enterGroupIdascom.packt,ArtifactIdaswebstore.Then,selectPackagingas
warandclickontheFinishbutton,asshowninthefollowingscreenshot:
Whatjusthappened?
Wejustcreatedthebasicprojectstructure.AnyJavaprojectfollowsacertaindirectory
structuretoorganizeitssourcecodeandstaticresources.Insteadofmanuallycreatingthe
wholedirectoryhierarchybyourselves,wejusthandedoverthatjobtoSTS.Bycollecting
somebasicinformationaboutourproject,suchasGroupId,ArtifactId,andthe
Packagingstylefromus,itisclearthatSTSissmartenoughtocreatethewholeproject
directorystructurewiththehelpoftheMavenplugin.Actually,whatishappeningbehind
thescreenisthatSTSisinternallyusingMaventocreatetheprojectstructure.
Wewantourprojecttobedeployableinanyservletcontainer-basedwebserver,suchas
Tomcat,andthat’swhyweselectedthePackagingstyleaswar.Afterexecutingstep4,
youwillseetheprojectstructureinPackageExplorer,asshowninthefollowing
screenshot:
Theprojectstructureoftheapplication
SpringMVCdependencies
AswearegoingtouseSpringMVCAPIsheavilyinourproject,weneedtheSpringjars
inourprojectduringthedevelopment.AsIalreadymentioned,Mavenwilltakecareof
managingdependenciesandpackagingtheproject.
Timeforaction–addingSpringjarsto
theproject
Let’stakealookathowwecanaddthespring-relatedjarsviatheMavenconfiguration:
1. Openpom.xml;youcanfindpom.xmlundertherootdirectoryoftheprojectitself.
2. Youwillseesometabsatthebottomofthepom.xmlfile.Ifyoudonotseethesetabs,
thenright-clickonpom.xmlandselecttheOpenWithoptionfromthecontextmenu
andchooseMavenPOMeditor.SelecttheDependenciestabandclickontheAdd
buttonintheDependenciessection.Don’tgetconfusedwiththeAddbuttonofthe
DependenciesManagementsection.YoushouldchoosetheAddbuttonintheleft-
handsidepane.
3. ASelectDependencywindowwillappear;enterGroupIdas
org.springframework,ArtifactIdasspring-webmvc,andVersionas
4.0.3.RELEASE.SelectScopeascompileandthenclickontheOKbutton,asshown
inthefollowingscreenshot:
4. Similarly,addthedependencyforJavaServerPagesStandardTagLibrary(JSTL)
byclickingonthesameAddbutton;thistime,enterGroupIdasjavax.servlet,
ArtifactIdasjstl,Versionas1.2,andselectScopeascompile.
5. Finally,addonemoredependencyforservlet-api;repeatthesamestepwithGroup
Idasjavax.servlet,ArtifactIdasjavax.servlet-api,andVersionas3.1.0,but
thistime,selectScopeasprovidedandthenclickontheOKbutton.
6. Asalaststep,don’tforgettosavethepom.xmlfile.
Whatjusthappened?
IntheMavenworld,pom.xml(ProjectObjectModel)istheconfigurationfilethatdefines
therequireddependencies.Whilebuildingourproject,Mavenwillreadthatfileandtryto
downloadthespecifiedjarsfromtheMavencentralbinaryrepository.YouneedInternet
accessinordertodownloadjarsfromMaven’scentralrepository.Mavenusesan
addressingsystemtolocateajarinthecentralrepository,whichconsistsofGroupId,
ArtifactId,andVersion.
Everytimeweaddadependency,anentrywillbemadewithinthe<dependencies></
dependencies>tagsinthepom.xmlfile.Forexample,ifyougotothepom.xmltabafter
finishingstep3,youwillseeanentryforspring-mvcasfollowswithinthe
<dependencies></dependencies>tag:
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>4.0.3.RELEASE</version>
</dependency>
Weaddedthedependencyforspring-mvcinstep3,andinstep4,weaddedthe
dependencyforJSTL.JSTLisacollectionofusefulJSPtagsthatcanbeusedtowriteJSP
pageseasily.Finally,weneedaservlet-apijarinordertouseservlet-relatedcode;thisis
whatweaddedinstep5.
However,thereisalittledifferenceinthescopeoftheservlet-apidependencycompared
totheothertwodependencies.Weonlyneedservlet-apiwhilecompilingourproject.
Whilepackagingourprojectaswar,wedon’twanttotheshipservlet-apijaraspartofour
project.ThisisbecausetheTomcatwebserverwouldprovidetheservlet-apijarwhile
deployingourproject.Thisiswhyweselectedthescopeasprovidedfortheservlet-api.
Afterfinishingstep6,youwillseeallthedependentjarsconfiguredinyourproject,as
showninthefollowingscreenshot,undertheMavenDependencieslibrary:
Weaddedonlythreejarsasourdependencies,butifyounoticeinourMavendependency
librarylist,youwillseemorethanthreejarentries.Canyouguesswhy?Whatifour
dependentjarshaveadependencyonotherjarsandsoon?
Forexample,ourspring-mvcjarisdependentonthespring-core,spring-context,and
spring-aopjars,butwehavenotspecifiedthosejarsinourpom.xmlfile;thisiscalled
transitivedependenciesintheMavenworld.Inotherwords,wecansaythatourproject
istransitivelydependentonthesejars.Mavenwillautomaticallydownloadallthese
transitivedependentjars;thisisthebeautyofMaven.Itwilltakecareofallthe
dependencymanagementautomatically;weneedtoinformMavenonlyaboutthefirst
leveldependencies.
Timeforaction–addingJavaversion
propertiesinpom.xml
Wesuccessfullyaddedalltherequiredjarstoourproject,butweneedtoperformone
smallconfigurationinourpom.xmlfile,thatis,tellingMaventouseJavaVersion7while
buildingourproject.HowdowetellMaventodothis?Simplyaddtwopropertyentriesin
pom.xml.Let’sdothis.
1. Openpom.xml.Youwillseesometabsatthebottomofpom.xml;selecttheOverview
tabfromthebottomofpom.xml,expandthepropertiesaccordion,andclickonthe
Createbutton.
2. Now,anAddpropertywindowwillappear;enterNameasmaven.compiler.source
andValueas1.7.
AddingtheJavacompilerversionpropertiestoPOM
3. Similarly,createonemorepropertywithNameasmaven.compiler.targetand
Valueas1.7.
4. Finally,savepom.xml.
Ajump-starttoMVC
Wecreatedourprojectandaddedalltherequiredjars,sowearereadytocode.Weare
goingtoincrementallybuildanonlinewebstorethroughoutthisbook,chapterbychapter.
Asafirststep,let’screateahomepageinourprojecttowelcomeourcustomers.
Ouraimissimple;whenweenterthehttp://localhost:8080/webstore/URLonthe
browser,wewouldliketoshowawelcomepagethatissimilartothefollowing
screenshot:
Don’tworryifyouarenotabletounderstandsomeofthecode;wearegoingtotakea
lookateachconceptindetailintheupcomingchapters.Asofnow,ouraimistohave
quickhands-onexperienceofdevelopingasimplewebpageusingSpringMVC.
Timeforaction–addingawelcomepage
Tocreateandaddawelcomepage,weneedtoexecutethefollowingsteps:
1. CreateaWEB-INF/jsp/directorystructureunderthesrc/main/webapp/directory;
createajspviewfilecalledwelcome.jspunderthesrc/main/webapp/WEB-INF/jsp/
directory,andaddthefollowingcodesnippetsintoitandsaveit:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<head>
<metahttp-equiv="Content-Type"content="text/html;charset=ISO-8859-
1">
<linkrel="stylesheet"
href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<title>Welcome</title>
</head>
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1>${greeting}</h1>
<p>${tagline}</p>
</div>
</div>
</section>
</body>
</html>
2. CreateaclasscalledHomeControllerunderthecom.packt.webstore.controller
packageinthesourcedirectorysrc/main/java,andaddthefollowingcodeintoit:
packagecom.packt.webstore.controller;
importorg.springframework.stereotype.Controller;
importorg.springframework.ui.Model;
importorg.springframework.web.bind.annotation.RequestMapping;
@Controller
publicclassHomeController{
@RequestMapping("/")
publicStringwelcome(Modelmodel){
model.addAttribute("greeting","WelcometoWebStore!");
model.addAttribute("tagline","Theoneandonlyamazingwebstore");

return"welcome";
}
}
Whatjusthappened?
Instep1,wejustcreatedaJSPview;theimportantthingweneedtonoticehereisthe
<h1>tagandthe<p>tag.Boththetagshavesomeexpressionthatissurroundedbycurly
bracesandprefixedbythe$symbol:
<h1>${greeting}</h1>
<p>${tagline}</p>
So,whatisthemeaningof${greeting}?Itmeansthatgreetingisakindofvariable;
duringtherenderingofthisJSPpage,thevaluestoredinthegreetingvariablewillbe
shownintheheader1style,andsimilarly,thevaluestoredinthetaglinevariablewillbe
shownasaparagraph.
Sonow,thenextquestionofwherewewillassignvaluestothosevariablesarises.Thisis
wherethecontrollerwillbeofhelp;withinthewelcomemethodoftheHomeController
class,takealookatthefollowinglinesofcode:
model.addAttribute("greeting","WelcometoWebStore!");
model.addAttribute("tagline","Theoneandonlyamazingwebstore");
Youcanobservethatthetwovariablenames,greetingandtagline,arepassedasafirst
parameteroftheaddAttributemethodandthecorrespondingsecondparameteristhe
valueforeachvariable.Sowhatwearedoinghereissimplyputtingtwostrings,"Welcome
toWebStore!"and"Theoneandonlyamazingwebstore",intothemodelwiththeir
correspondingkeysasgreetingandtagline.Asofnow,simplyconsiderthefactthat
modelisakindofmap.Folkswithknowledgeofservletprogrammingcanconsiderthe
factthatmodel.addAttributeworksexactlylikerequest.setAttribute.
So,whatevervalueweputintothemodelcanberetrievedfromtheview(jsp)usingthe
correspondingkeywiththehelpofthe${}placeholderexpressionnotation.
Thedispatcherservlet
Wecreatedacontrollerthatcanputvaluesintothemodel,andwecreatedtheviewthat
canreadthosevaluesfromthemodel.So,themodelactsasanintermediatebetweenthe
viewandthecontroller;withthis,wehavefinishedallthecodingpartrequiredtopresent
thewelcomepage.Sowillwebeabletorunourprojectnow?No;atthisstage,ifwerun
ourprojectandenterthehttp://localhost:8080/webstore/URLonthebrowser,we
willgetanHTTPStatus404error.Thisisbecausewehavenotperformedanyservlet
mappingyet.InaSpringMVCproject,wemustconfigureafrontservletmapping.The
frontservlet(sometimescalledthefrontcontroller)mappingisadesignpatternwhereall
requestsforaparticularwebapplicationaredirectedtothesameservlet.Onesuchfront
servletgivenbySpringMVCframeworkisthedispatcherservlet
(org.springframework.web.servlet.DispatcherServlet).Wehavenotconfigureda
dispatcherservletforourprojectyet;thisiswhywegettheHTTPStatus404error.
Timeforaction–configuringthe
dispatcherservlet
ThedispatcherservletiswhatexaminestheincomingrequestURLandinvokestheright
correspondingcontrollermethod.Inourcase,thewelcomemethodfromthe
HomeControllerclassneedstobeinvokedifweenterthe
http://localhost:8080/webstore/URLonthebrowser.Solet’sconfigurethe
dispatcherservletforourproject:
1. Createweb.xmlunderthesrc/main/webapp/WEB-INF/directoryinyourprojectand
enterthefollowingcontentinsideweb.xmlandsaveit:
<web-appversion="3.0"xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
<servlet>
<servlet-name>DefaultServlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet
</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>DefaultServlet</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>
2. NowcreateonemorexmlfilecalledDefaultServlet-servlet.xmlunderthesame
src/main/webapp/WEB-INF/directoryandenterthefollowingcontentintoitand
saveit:
<?xmlversion="1.0"encoding="UTF-8"?>
<beansxmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd">
<mvc:annotation-driven/>
<context:component-scanbase-package="com.packt.webstore"/>

<bean
class="org.springframework.web.servlet.view.InternalResourceViewResolver
">
<propertyname="prefix"value="/WEB-INF/jsp/"/>
<propertyname="suffix"value=".jsp"/>
</bean>
</beans>
Whatjusthappened?
Ifyouknowaboutservletprogramming,youmightbequitefamiliarwiththeservlet
configurationandweb.xml.Inweb.xml,weconfiguredaservletnamedDefaultServlet,
whichismoreorlesssimilartoanyothernormalservletconfiguration.Theonly
differenceisthatwehavenotcreatedanyservletclassforthatconfiguration.Instead,the
servletclass(org.springframework.web.servlet.DispatcherServlet)isprovidedby
theSpringMVCframework,andwemakeuseofitinweb.xml.Afterthisstep,our
configuredDispatcherServlet(DefaultServlet)willbereadytohandleanyrequests
thatcometoourapplicationonruntimeandwilldispatchtherequesttothecorrect
controller’smethod.
However,DispatcherServletshouldknowwhereourcontrollersandviewfilesare
locatedinourproject,andonlythencanitproperlydispatchtherequesttothecorrect
controllers.SowehavetogivesomehinttoDispatcherServlettolocatethecontrollers
andviewfiles.Thisiswhatweconfiguredinstep2throughtheDispatcherServlet-
servlet.xmlfile.
Don’tworryifyouarenotabletounderstandeachandeveryconfigurationinweb.xmland
DispatcherServlet-servlet.xml;wewilltakealookattheseconfigurationfilesinnext
chapter.Asofnow,justrememberthatthisisaone-timeconfigurationthatisneededto
runourprojectsuccessfully.
Deployingourproject
Wesuccessfullycreatedtheprojectinthelastsection,soyoumightbecurioustoknow
whatwouldhappenifwerunourprojectnow.Asourprojectisawebproject,weneeda
webservertorunit.
Timeforaction–runningtheproject
AswealreadyconfiguredtheTomcatwebserverinourSTS,let’suseTomcattodeploy
andrunourproject:
1. Right-clickonyourprojectfromPackageExplorerandnavigatetoRunAs|Run
onServer.
2. Aserverselectionwindowwillappearwithalltheavailableserverslisted;justselect
theserverthatwehaveconfigured,Tomcatv7.0.
3. Atthebottomofthewindow,youcanseeacheckboxwiththecaptionthatsays
Alwaysusethisserverwhenrunningthisproject;selectthischeckboxandenter
theFinishbutton,asshowninthefollowingscreenshot:
ConfiguringthedefaultserverforaSpringMVCproject
4. Nowyouwillseeawebpagethatwillshowyouawelcomemessage.
Summary
Inthischapter,wesawhowtoinstallalltheprerequisitesthatareneededtogetstartedand
runourfirstSpringMVCapplication,forexample,installingJDK,theMavenbuildtool,
theTomcatservletcontainer,andSTSIDE.
WealsolearnedhowtoperformvariousconfigurationsinourSTSIDEforMavenand
Tomcat,createdourfirstSpringMVCproject,andaddedallSpring-relateddependentjars
throughtheMavenconfiguration.
Wehadaquickhands-onexperienceofdevelopingawelcomepageforourwebstore
application.Duringthatcourse,welearnedhowtoputvaluesintoamodelandhowto
retrievethesevaluesfromthemodel.
WhateverwehaveseensofarisjustaglimpseofSpringMVC,butthereismuchmoreto
uncover,forexample,howthemodelandviewcontrollerareconnectedtoeachotherand
howtherequestflowoccurs.Wearegoingtoexplorethesetopicsinthenextchapter,so
seeyouthere!
Chapter2.SpringMVCArchitecture–
ArchitectingYourWebStore
WhatwesawinthefirstchapterisnothingbutaglimpseofSpringMVC;intheprevious
chapter,ourtotalfocuswasjustongettingittorunaSpringMVCapplication.Now,it’s
timeforustodeep-diveintoSpringMVCarchitecture.
Bytheendofthischapter,youwillhaveaclearunderstandingof:
Thedispatcherservletandrequestmapping
Thewebapplicationcontextandconfiguration
TheSpringMVCrequestflowandWebMVC
Thewebapplicationarchitecture
Thedispatcherservlet
Inthefirstchapter,wewereintroducedtothedispatcherservletandsawhowtodefinea
dispatcherservletinweb.xml.Welearnedthateverywebrequestfirstcomestothe
dispatcherservlet.Thedispatcherservletistheonethatdecidesthecontrollermethodthat
itshoulddispatchthewebrequestto.Inthepreviouschapter,wecreatedawelcomepage
thatwillbeshownwheneverweentertheURLhttp://localhost:8080/webstore/on
thebrowser.MappingaURLtotheappropriatecontrollermethodistheprimarydutyofa
dispatcherservlet.
SothedispatcherservletreadsthewebrequestURLandfindstheappropriatecontroller
methodthatcanservethatwebrequestandinvokesit.Thisprocessofmappingaweb
requesttoaspecificcontrollermethodiscalledrequestmapping,andthedispatcher
servletisabletodothiswiththehelpofthe@RequestMappingannotation
(org.springframework.web.bind.annotation.RequestMapping).
Timeforaction–examiningrequest
mapping
Let’sobservewhatwillhappenwhenyouchangethevalueattributeofthe
@RequestMappingannotationbyexecutingthefollowingsteps:
1. OpenyourSTSandrunthewebstoreproject;justright-clickonyourprojectand
chooseRunAs|RunonServer.Youwillbeabletoviewthesamewelcome
messageonthebrowser.
2. Now,gototheaddressbarofthebrowserandentertheURL,
http://localhost:8080/webstore/welcome.
3. YouwillseetheHTTPStatus404errorpageonthebrowser,andyouwillalsosee
thefollowingwarningintheconsole:
WARNING:NomappingfoundforHTTPrequestwithURI[/webstore/welcome]
inDispatcherServletwithname'DefaultServlet'
Anerrorlogdisplayingthe“Nomappingfound”warningmessage
4. Now,opentheHomeControllerclass,changethe@RequestMappingannotation’s
valueattributeto/welcome,andsaveit.Basically,yournewrequestmapping
annotationwilllooklike@RequestMapping("/welcome").
5. Again,runtheapplicationandenterthesameURLthatyouenteredinstep2;now
youwillbeabletoseethesamewelcomemessageonthebrowser,withoutany
requestmappingerror.
6. Finally,opentheHomeControllerclassandrevertthechangesthatweremadetothe
@RequestMappingannotation’svalue;justmakeit@RequestMapping("/")againand
saveit.
Whatjusthappened?
Afterstartingourapplication,whenweentertheURL
http://localhost:8080/webstore/welcomeonthebrowser,thedispatcherservlet
(org.springframework.web.servlet.DispatcherServlet)immediatelytriestofinda
matchingcontrollermethodfortherequestpath,/welcome.
Tip
InaSpringMVCapplication,theURLcanlogicallybedividedintofiveparts(seethe
followingfigure);the@RequestMappingannotationonlymatchesagainsttheURLrequest
path.Itomitsthescheme,hostname,applicationname,andsoon.
The@RequestMappingannotationhasonemoreattributecalledmethodtofurthernarrow
downthemappingbasedontheHTTPrequestmethodtypes(GET,POST,HEAD,OPTIONS,
PUT,DELETE,andTRACE).Ifwedonotspecifythemethodattributeinthe
@RequestMappingannotation,thedefaultmethodwillbeGET.Wewilllearnmoreabout
themethodattributeofthe@RequestMappingannotationinChapter4,WorkingwithSpring
TagLibraries,underthesectiononformprocessing.
ThelogicalpartsofatypicalSpringMVCapplicationURL
Sincewedon’thaveacorrespondingrequestmappingforthegivenURLpath,/welcome,
wegettheHTTPStatus404erroronthebrowserandthefollowingerrorlogonthe
console:
WARNING:NomappingfoundforHTTPrequestwithURI[/webstore/welcome]in
DispatcherServletwithname'DefaultServlet'
Fromtheerrorlog,wecanclearlyunderstandthatthereisnorequestmappingforthe
URLpath,/webstore/welcome.So,wetrytomapthisURLpathtotheexistingcontroller
method;that’swhy,instep4,weputonlytherequestpathvalue,/welcome,inthe
@RequestMappingannotationasthevalueattribute.Noweverythingworksperfectlyfine.
Finally,werevertedour@RequestMappingannotation’svalueto/againinstep6.Whydid
wedothis?BecausewewantittoshowthewelcomepageunderthewebrequestURL
http://localhost:8080/webstore/again.Observecarefullythatherethelastsingle
character/istherequestpath.Wewillseemoreaboutrequestmappinginupcoming
chapters.
Popquiz–requestmapping
Q1.IfwehaveaSpringMVCapplicationforlibrarymanagementcalledBookPediaand
wanttomapawebrequestURL,
http://localhost:8080/BookPedia/category/fiction,toacontrollermethod,how
willweformthe@RequestMappingannotation?
1. @RequestMapping("/fiction").
2. @RequestMapping("/category/fiction").
3. @RequestMapping("/BookPedia/category/fiction").
Thewebapplicationcontext
InaSpring-basedapplication,ourapplicationobjectslivewithinanobjectcontainer.This
containercreatesobjectsandassociationsbetweenobjects,andmanagestheircomplete
lifecycle.ThesecontainerobjectsarecalledSpring-managedbeans(orsimplybeans),and
thecontaineriscalledanapplicationcontextintheSpringworld.
ASpringcontainerusesdependencyinjection(DI)tomanagethebeansthatmakeupan
application.Anapplicationcontext
(org.springframework.context.ApplicationContext)createsbeansandassociate
beanstogetherbasedonthebeanconfigurationanddispensesbeansonrequest.Abean
configurationcanbedefinedviaanXMLfile,annotation,orevenviaJavaconfiguration
classes.WewilluseonlyXML-andannotation-basedbeanconfigurationsinourchapters.
Awebapplicationcontextistheextensionofanapplicationcontext,designedtowork
withthestandardservletcontext(javax.servlet.ServletContext).Awebapplication
contexttypicallycontainsfrontend-relatedbeans,suchasviewsandviewresolvers.Inthe
firstchapter,wecreatedanXMLfilecalledDefaultServlet-servlet.xml,whichis
nothingbutabeanconfigurationfileforourwebapplicationcontext.
Timeforaction–understandingtheweb
applicationcontext
Youhavereceivedenoughofanintroductiononthewebapplicationcontext;now,tweaka
littlebitwiththenameandlocationofthewebapplicationcontextconfigurationfile
(DefaultServlet-servlet.xml)andobservetheeffect.Performthefollowingsteps:
1. RenametheDefaultServlet-servlet.xmlfiletoDispatcherServlet-
servlet.xml;youcanfindDefaultServlet-servlet.xmlunderthe
src/main/webapp/WEB-INF/directory.
2. Then,runyourwebstoreprojectagainandentertheURL,
http://localhost:8080/webstore/;youwillseeanHTTPStatus500error
messageonyourwebpageandaFileNotFoundExceptionerrorinthestacktraceas
follows:
java.io.FileNotFoundException:CouldnotopenServletContextresource
[/WEB-INF/DefaultServlet-servlet.xml]
AnerrormessagedisplayingFileNotFoundExceptionforDefaultServlet-servlet.xml
3. Tofixthiserror,changethenameofDefaultServlettoDispatcherServletin
web.xml;basically,afterchangingthenametoDispatcherServlet,yourservlet
configurationwilllooklikethefollowingintheweb.xmlfile:
<servlet>
<servlet-name>DispatcherServlet</servlet-name>
<servlet-
class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>DispatcherServlet</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
4. Now,runyourapplicationandentertheURL,http://localhost:8080/webstore/;
youwillseethewelcomemessageagain.
5. RenameyourDispatcherServlet-servlet.xmlfiletoDispatcherServlet-
context.xmloncemore.
6. Next,createadirectorystructurespring/webcontext/undertheWEB-INFdirectory
andmovetheDispatcherServlet-context.xmlfiletothesrc/main/webapp/WEB-
INF/spring/webcontext/directory.
7. Then,runyourapplication,andyouwillseeanHTTPStatus500errormessageon
yourwebpageagainandaFileNotFoundExceptionerrormessageinthestacktrace:
java.io.FileNotFoundException:CouldnotopenServletContextresource
[/WEB-INF/DispatcherServlet-servlet.xml]
8. Tofixthiserror,addthefollowingtagswithinthe<servlet>and</servlet>tags
inweb.xmlasshowninthefollowingcode:
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>
/WEB-INF/spring/webcontext/DispatcherServlet-context.xml
</param-value>
</init-param>
9. Now,runtheapplicationagainandentertheURL,
http://localhost:8080/webstore/;youwillbeabletoseethewelcomemessage
again.
Whatjusthappened?
So,whatwedidfirstwasrenamedtheDefaultServlet-servlet.xmlfileto
DispatcherServlet-servlet.xml,andwegotaFileNotFoundExceptionerrorat
runtime,asfollows:
java.io.FileNotFoundException:CouldnotopenServletContextresource
[/WEB-INF/DefaultServlet-servlet.xml]
Tofixtheerror,wechangedourdispatcherservletconfiguration,asfollows,inthe
web.xmlfile:
<servlet>
<servlet-name>DispatcherServlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet
</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>DispatcherServlet</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
WechangedtheservletnametoDispatcherServletinordertoalignwiththeweb
applicationcontextconfigurationfilenamedDispatcherServlet-servlet.xml.So,based
onthisexercise,wecanlearnthatduringthestart-upofanySpringMVCproject,the
dispatcherservletwilllookforawebapplicationcontextconfigurationfileofthepattern
<ConfigureddispatcherServletName>-servlet.xmlundertheWEB-INFdirectory.It
isourresponsibilitytokeepthewebapplicationcontextconfigurationfileundertheWEB-
INFdirectorywiththerightname.However,whatifwewishtokeepthefileinsomeother
directory?
Tip
Oneoftheimportantthingstobenotedin<servlet-mapping>isthevalueofthe<url-
pattern>/</url-pattern>tag.Byassigning/astheURLpatternforthedispatcher
servlet,wemakeDispatcherServletthedefaultservletforourwebapplication.So,
everywebrequestcomingtoourwebapplicationwillbehandledbyDispatcherServlet.
Forinstance,insteps5and6,werenamedthewebapplicationcontextconfigurationfile
andmovedittoacompletelynewdirectory(src/main/webapp/WEB-
INF/spring/webcontext/).Inthatcase,howdidwefixtheHTTPStatus500error?The
answerlieswithinapropertycalledcontextConfigLocation.Forthedispatcherservletto
locatethewebcontextconfigurationfileeasily,wegavethelocationofthisfiletothe
dispatcherservletthroughapropertycalledcontextConfigLocation.That’swhywe
addedthispropertytothedispatcherservletinstep8,asfollows:
<servlet>
<servlet-name>DispatcherServlet</servlet-name>
<servlet-
class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>
/WEB-INF/spring/webcontext/DispatcherServlet-context.xml
</param-value>
</init-param>
</servlet>
Now,weareabletorunourapplicationwithoutanyproblem.Okay,weplayedalotwith
thewebapplicationcontextconfigurationfileandlearnedthatthedispatcherservlet
shouldknowaboutthewebapplicationcontextconfigurationfileduringthestart-upof
ourproject.Sothenextquestionis:whyisthedispatcherservletlookingforthisweb
contextconfigurationfile,andwhatisdefinedinsidethisfile?Let’sfindouttheanswer,
butbeforethat,youmayanswerthefollowingpopquizquestionstomakesureyou
understandtheconceptofthewebapplicationcontextconfiguration.
Popquiz–thewebapplicationcontext
Q1.IfthecontextConfigLocationpropertywasnotconfiguredinourdispatcherservlet
configuration,underwhichlocationwouldSpringMVClookforthewebapplication
contextconfigurationfile?
1. IntheWEB-INFdirectory
2. InWEB-INF/spring
3. InWEB-INF/spring/appServlet
Q2.IfwedonotwanttoprovidecontextConfigLocationtothefollowingdispatcher
servletconfiguration,howdoweavoidtheHTTPStatus500error?
<servlet>
<servlet-name>FrontController</servlet-name>
<servlet-
class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
</servlet>
1. BycreatingacontextfilecalledFrontController-context.xmlintheWEB-INF
directory
2. BycreatingafilecalledDispatcherServlet-context.xmlinWEB-INF
3. BycreatingafilecalledFrontController-servlet.xmlinWEB-INF
Thewebapplicationcontextconfiguration
Thewebapplicationcontextconfigurationfile(DispatcherServlet-context.xml)is
nothingbutasimpleSpringbeanconfigurationfile.Springwillcreatebeans(objects)for
everybeandefinitionmentionedinthisfileduringbootupofourapplication.Ifyouopen
thiswebapplicationcontextconfigurationfile(/WEB-
INF/spring/webcontext/DispatcherServlet-context.xml),youwillfindsome
configurationandbeandefinitionasfollows:
<?xmlversion="1.0"encoding="UTF-8"?>
<beansxmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd">
<mvc:annotation-driven/>
<context:component-scanbase-package="com.packt.webstore"/>

<bean
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<propertyname="prefix"value="/WEB-INF/jsp/"/>
<propertyname="suffix"value=".jsp"/>
</bean>
</beans>
Thefirsttagwithinthe<beans>definitionis<mvc:annotation-driven/>.Bythistag,
wetellSpringMVCtoconfiguretheDefaultAnnotationHandlerMapping,
AnnotationMethodHandlerAdapter,andExceptionHandlerExceptionResolverbeans.
ThesebeansarerequiredforSpringMVCtodispatchrequeststothecontrollers.
Actually<mvc:annotation-driven/>doesmanythingsbehindthescreen.Italso
enablessupportforvariousconvenientannotationssuchas@NumberFormatand
@DateTimeFormattoformattheformbeanfieldsduringformbinding.Similarly,wehave
the@Validannotationtovalidatethecontrollermethod’sparameters.ItalsosupportsJava
objectsto/fromanXMLorJSONconversionviathe@RequestBodyand@ResponseBody
annotationsinthe@RequestMappingor@ExceptionHandlermethodduringformbinding.
Wewillseetheusageoftheseannotationsinlaterchapters.Asofnow,justrememberthat
the<mvc:annotation-driven/>tagisneededtoenableannotationssuchas
@controllerand@RequestMapping.
Whatisthepurposeofthesecondtag,<context:component-scan>?Youneedabitof
backgroundinformationtounderstandthepurposeofthe<context:component-scan>tag.
The@Controllerannotationindicatesthataparticularclassservestheroleofacontroller.
Wealreadylearnedthatthedispatcherservletsearchessuchannotatedclassesformapped
methods(the@RequestMappingannotatedmethods)toserveawebrequest.Inorderto
makethecontrolleravailableforsearching,weneedtocreateabeanforthiscontrollerin
ourwebapplicationcontext.
Wecancreatebeansforcontrollersexplicitlyviathebeanconfiguration(usingthe<bean>
tag—youcanseehowwecreatedabeanfortheInternalResourceViewResolverclass
usingthe<bean>taginthenextsection),orwecanhandoverthattasktoSpringviathe
autodetectionmechanism.Toenabletheautodetectionofthe@Controllerannotated
classes,weneedtoaddcomponentscanningtoourconfigurationusingthe
<context:component-scan>tag.Now,youfinallyunderstandthepurposeofthe
<context:component-scan>tag.
Springwillcreatebeans(objects)forevery@Controllerclassatruntime.Thedispatcher
servletwillsearchforthecorrectrequestmappingmethodinevery@Controllerbean
basedonthe@RequestMappingannotation,toserveawebrequest.Thebase-package
propertyofa<context:component-scan>tagindicatesthepackageunderwhichSpring
shouldsearchforcontrollerclassestocreatebeans:
<context:component-scanbase-package="com.packt.webstore"/>
TheprecedinglineinstructsSpringtosearchforcontrollerclasseswithinthe
com.packt.webstorepackageanditssubpackages.
Tip
The<context:component-scan>tagnotonlyrecognizescontrollerclasses,italso
recognizesotherstereotypessuchasservicesandrepositoryclassesaswell.Wewilllearn
moreaboutservicesandrepositorieslater.
Popquiz–webapplicationcontextconfiguration
Q1.WhatneedstobedonetoidentifyaclassbySpringasacontroller?
1. Thatparticularclassshouldhavethe@Controllerannotation.
2. The<mvc:annotation-driven/>and<context:component-scan>tagsshouldbe
specifiedinthewebapplicationcontextconfigurationfile.
3. Thatparticularclassshouldbeputupinapackageorsubpackagethathasbeen
specifiedasabasepackageinthe<context:component-scan>tag.
4. Alloftheabove.
Viewresolvers
Wesawthepurposeofthefirsttwotagsthatarespecifiedwithinthewebapplication
contextconfigurationfile:
<mvc:annotation-driven/>
<context:component-scanbase-package="com.packt.webstore"/>
Basedonthesetags,Springcreatesthenecessarybeanstohandleawebrequestandalso
createsbeansforallthe@Controllerclasses.However,torunaSpringMVCapplication
successfully,Springneedsonemorebean;thisbeaniscalledaviewresolver.
Aviewresolverhelpsthedispatcherservletidentifytheviewsthathavetoberenderedas
theresponseforaspecificwebrequest.SpringMVCprovidesvariousviewresolver
implementationstoidentifyviews,andInternalResourceViewResolverisonesuch
implementation.Thefinaltaginthewebapplicationcontextconfigurationisthebean
definitionfortheInternalResourceViewResolverclassasfollows:
<bean
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<propertyname="prefix"value="/WEB-INF/jsp/"/>
<propertyname="suffix"value=".jsp"/>
</bean>
Throughtheprecedingbeandefinitioninthewebapplicationcontextconfiguration,we
instructSpringMVCtocreateabeanfortheInternalResourceViewResolverclass
(org.springframework.web.servlet.view.InternalResourceViewResolver).Wewill
learnmoreabouttheviewresolverinChapter5,WorkingwithViewResolver.
Timeforaction–understanding
InternalResourceViewResolver
WeinstructSpringtocreateabeanforanInternalResourceViewResolverclass,but
why?Whoisgoingtousethisbean?Whatistheroleofthe
InternalResourceViewResolverbeaninSpringMVC?Findtheanswertothese
questionsthroughthefollowingexercise:
1. OpenDispatcherServlet-context.xml;youcanfindthisfileunderthe
src/main/webapp/WEB-INF/spring/webcontext/directoryinyourproject.
2. ChangetheprefixpropertyvalueoftheInternalResourceViewResolverbeanas
follows:
<propertyname="prefix"value="/WEB-INF/views/"/>
3. Now,runyourwebstoreprojectagainandentertheURL
http://localhost:8080/webstore/.YouwillseeanHTTPStatus404error
messageinyourbrowserasshowninthefollowingscreenshot:
Anerrorpagedisplayingthenoresourcefoundmessage
4. Then,renamethejspdirectory(/src/main/webapp/WEB-INF/jsp)toviews.
5. Finally,runyourapplicationandentertheURL,
http://localhost:8080/webstore/.Youwillseethewelcomemessageagain.
Whatjusthappened?
AfterchangingtheprefixpropertyvalueoftheInternalResourceViewResolverbean,
wegotanHTTPStatus404errorwhenweenteredtheURL,
http://localhost:8080/webstore/,inthebrowser.TheHTTPStatus404errormeans
thattheservercouldnotfindthewebpagethatweaskedfor.Ifthatisthecase,thenwhich
webpagedidweaskfor?
Asamatteroffact,wedidn’taskforanywebpagefromtheserverdirectly;instead,the
dispatcherservletasksaparticularwebpagefromtheserver.Whatwealreadylearnedis
thatthedispatcherservletinvokesamethodinanyofthecontrollerbeansthatcanserve
thiswebrequest.Inourcase,thismethodisnothingbutthewelcomemethodofour
HomeControllerclass,becausethisistheonlyrequestmappingmethodthatcanmatch
therequestpathofthegivenURL,http://localhost:8080/webstore/,inits
@RequestMappingannotation.
Now,observethefollowing:
TheprefixpropertyvalueoftheInternalResourceViewResolverbeandefinitionin
DispatcherServlet-context.xml;thatis,/WEB-INF/views/
ThereturnvalueofthewelcomemethodfromtheHomeControllerclass;thatis,
welcome
Finally,thesuffixpropertyvalueoftheInternalResourceViewResolverbean,that
is,.jsp
Ifyoucombinethesethreevaluestogether,youwillgetawebpagerequestURL:/WEB-
INF/views/welcome.jsp.Now,notetheerrormessageinthepreviousscreenshot,
showingtheHTTPStatus404errorforthesamewebpageURL:/WEB-
INF/views/welcome.jspundertheapplicationname,webstore/.
So,theconclusionisthatInternalResourceViewResolverresolvestheactualviewfile
pathbyprependingtheconfiguredprefixvalueandappendingthesuffixvaluewiththe
viewname—theviewnameisthevalueusuallyreturnedbythecontrollermethod.So,the
controllermethoddoesn’treturnthepathoftheactualviewfile;itreturnsonlythelogical
viewname.ItisthejobofInternalResourceViewResolvertoformtheURLoftheactual
viewfilecorrectly.
WhoisgoingtousethisfinalformedURL?Theansweristhedispatcherservlet.After
gettingthefinalformedURLoftheviewfilefromtheviewresolver,thedispatcherservlet
willtrytogettheviewfilefromtheserver.Duringthistime,iftheformedURLisfound
tobewrong,thenyouwillgettheHTTPStatus404error.
Usually,afterinvokingthecontrollermethod,thedispatcherservletwillwaittogetthe
logicalviewnamefromit.Oncethedispatcherservletgetsthelogicalviewname,itgives
thisnametotheviewresolver(InternalResourceViewResolver)togettheURLpathof
theactualviewfile;oncetheviewresolverreturnstheURLpathtothedispatcherservlet,
therenderedviewfileisservedtotheclientbrowserasawebpagebythedispatcher
servlet.
However,whydidwegettheerrorinstep3?Sincewechangedtheprefixpropertyofthe
InternalResourceViewResolverbeaninstep2,theURLpathvaluereturnedfrom
InternalResourceViewResolverbecame/WEB-INF/views/welcome.jspinstep3,which
isaninvalidpathvalue(thereisnodirectorycalledviewsunderWEB-INF).That’swhy,we
renamedthedirectoryjsptoviewsinstep4toalignitwiththepathgeneratedby
InternalResourceViewResolversothateverythingworksfineagain.
ModelViewController
Sofar,wehaveseenlotsofconcepts,suchasthedispatcherservlet,requestmapping,
controllers,andviewresolver;itwouldbegoodtoseetheoverallpictureoftheSpring
MVCrequestflowsothatwecanunderstandeachcomponent’sresponsibilities.However,
beforethat,weneedtounderstandtheModelViewController(MVC)conceptsome
more.Everyenterprise-levelapplication’spresentationlayercanlogicallybedividedinto
thefollowingthreemajorparts:
Thepartthatmanagesthedata(Model)
Thepartthatcreatestheuserinterfaceandscreens(View)
Thepartthathandlesinteractionsbetweentheuser,userinterface,anddata
(Controller)
Thefollowingdiagramwillhelpyouunderstandtheeventflowandcommandflowwithin
anMVCpattern:
TheclassicMVCpattern
Wheneverauserinteractswiththeviewbyclickingonalinkorbutton,theviewissuesan
eventnotificationtothecontroller,andthecontrollerissuesacommandnotificationtothe
modeltoupdatethedata.Similarly,wheneverthedatainthemodelgetsupdatedor
changed,achangenotificationeventisissuedtotheviewbythemodelinresponse,and
theviewissuesastatequerycommandtothemodeltogetthelatestdatafromthemodel.
Here,themodelandviewcaninteractdirectly;thispatterniscalledtheclassicMVC
pattern.However,whatSpringMVCemploysissomethingcalledawebMVCpattern
duetothelimitationsintheHTTPprotocol.
Tip
WebapplicationsrelyontheHTTPprotocol,whichisastatelesspullprotocol.Thismeans
thatnorequestimpliesnoreply;everytime,weneedtorequesttheapplicationtoknowits
state.TheMVCdesignpatternrequiresapushprotocolfortheviewstobenotifiedbythe
model.SoinwebMVC,thecontrollertakesmoreresponsibilityforthestatechanging,
statequerying,andchangenotification.
InwebMVC,everyinteractionbetweenthemodelandviewistakenthroughthe
controlleronly.So,thecontrolleractsasabridgebetweenthemodelandview.Thereisno
directinteractionbetweenthemodelandview,asintheclassicMVCpattern.
AnoverviewoftheSpringMVCrequest
flow
ThemainentrypointforawebrequestinaSpringMVCapplicationisviathedispatcher
servlet.Thedispatcherservletactsasthefrontcontrolleranddispatchestherequeststothe
othercontroller.Thefrontcontroller’smaindutyistofindtheappropriatecontrollerto
handovertherequestforfurtherprocessing.Thefollowingdiagramshowsanoverviewof
therequestflowinaSpringMVCapplication:
TheSpringMVCrequestflow
Now,let’sreviewtheSpringMVCrequestflowinshort:
1. WhenweenteraURLinthebrowser,therequestcomestothedispatcherservlet.
Thedispatcherservletthenactsasacentralizedentrypointtothewebapplication.
2. Thedispatcherservletdeterminesasuitablecontrollerthatiscapableofhandlingthe
requestanddispatchingthisrequesttothecontroller.
3. Thecontrollermethodupdatesobjectsinthemodelandreturnsthelogicalviewname
andupdatedmodeltothedispatcherservlet.
4. Thedispatcherservletconsultswiththeviewresolvertodeterminewhichviewto
renderandpassesthemodeldatatothatview.
5. Theviewfurnishesthedynamicvaluesinthewebpageusingthemodeldata,renders
thefinalwebpage,andreturnsthiswebpagetothedispatcherservlet.
6. Attheend,thedispatcherservletreturnsthefinal,renderedpageasaresponsetothe
browser.
Thewebapplicationarchitecture
Now,weunderstandtheoverallrequestflowandresponsibilityofeachcomponentina
typicalSpringMVCapplication.However,thisisnotenoughforustobuildanonlineweb
storeapplication.Wealsoneedtoknowthebestpracticestodevelopanenterprise-level
webapplication.Oneofthebestpracticesinatypicalwebapplicationistoorganize
sourcecodeintolayers,whichwillimprovereusabilityandloosecoupling.Atypicalweb
applicationnormallyhasfourlayers:thepresentation,domain,services,andpersistence.
Sofar,whateverwehaveseen,suchasthedispatcherservlet,controllers,viewresolvers,
andsoon,isconsideredapartofthepresentationlayercomponents.Let’sunderstandthe
remaininglayersandcomponentsonebyone.
Thedomainlayer
Let’sstartwiththedomainlayer.Adomainlayertypicallyconsistsofadomainmodel.So,
whatisadomainmodel?Adomainmodelisarepresentationofthedatastoragetypes
requiredbythebusinesslogic.Itdescribesthevariousdomainobjects(entities);their
attributes,roles,andrelationships;plustheconstraintsthatgoverntheproblemdomain.
Takealookatthefollowingdomainmodeldiagramfororderprocessingtogetaquick
ideaaboutthedomainmodel:
Sampledomainmodel
Eachblockintheprecedingdiagramrepresentsabusinessentity,andthelinesrepresent
theassociationsbetweentheentities.Basedontheprecedingdomainmodeldiagram,we
canunderstandthat,inanorderprocessingdomain,acustomercanhavemanyorders,
eachordercanhavemanyorderitems,andeachorderitemrepresentsasingleproduct.
Duringcoding,thedomainmodelwillbeconvertedintocorrespondingdomainobjects
andassociationsbyadeveloper.Adomainobjectisalogicalcontainerofpuredomain
information.Sincewearegoingtobuildanonlinewebstoreapplication,inourdomain,
theprimarydomainobjectmightbeaproduct.So,let’sstartwiththedomainobjectto
representaproduct.
Timeforaction–creatingadomainobject
Sofar,inyourwebstore,youhaveshowedonlyawelcomemessage.Itisnowtimefor
youtoshowyourfirstproductonthewebpage.Dothisbycreatingadomainobject,as
follows,torepresenttheproductinformation:
1. CreateaclasscalledProductunderthecom.packt.webstore.domainpackageinthe
sourcefoldersrc/main/java.Now,addthefollowingcodeintoit:
packagecom.packt.webstore.domain;
importjava.math.BigDecimal;
publicclassProduct{
privateStringproductId;
privateStringname;
privateBigDecimalunitPrice;
privateStringdescription;
privateStringmanufacturer;
privateStringcategory;
privatelongunitsInStock;
privatelongunitsInOrder;
privatebooleandiscontinued;
privateStringcondition;
publicProduct(){
super();
}
publicProduct(StringproductId,Stringname,BigDecimalunitPrice){
this.productId=productId;
this.name=name;
this.unitPrice=unitPrice;
}
//addsettersandgettersforallthefieldshere
@Override
publicbooleanequals(Objectobj){
if(this==obj)
returntrue;
if(obj==null)
returnfalse;
if(getClass()!=obj.getClass())
returnfalse;
Productother=(Product)obj;
if(productId==null){
if(other.productId!=null)
returnfalse;
}elseif(!productId.equals(other.productId))
returnfalse;
returntrue;
}
@Override
publicinthashCode(){
finalintprime=31;
intresult=1;
result=prime*result
+((productId==null)?0:productId.hashCode());
returnresult;
}
@Override
publicStringtoString(){
return"Product[productId="+productId+",name="+name+"]";
}
}
Addsettersandgettersforallofthefieldsintheprecedingclass.Ihaveomitteditto
makethecodecompact,butitisamust,sopleasedoaddit.
2. Now,createonemoreclasscalledProductControllerunderthe
com.packt.webstore.controllerpackageinthesourcefoldersrc/main/javaand
addthefollowingcodeintoit:
packagecom.packt.webstore.controller;
importjava.math.BigDecimal;
importorg.springframework.stereotype.Controller;
importorg.springframework.ui.Model;
importorg.springframework.web.bind.annotation.RequestMapping;
importcom.packt.webstore.domain.Product;
@Controller
publicclassProductController{
@RequestMapping("/products")
publicStringlist(Modelmodel){
Productiphone=newProduct("P1234","iPhone5s",new
BigDecimal(500));
iphone.setDescription("AppleiPhone5ssmartphonewith4.00-inch
640x1136displayand8-megapixelrearcamera");
iphone.setCategory("SmartPhone");
iphone.setManufacturer("Apple");
iphone.setUnitsInStock(1000);

model.addAttribute("product",iphone);

return"products";
}
}
3. Finally,addonemoreJSPviewfilecalledproducts.jspunderthedirectory
src/main/webapp/WEB-INF/views/,addthefollowingcodesnippetsintoit,andsave
it:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<head>
<metahttp-equiv="Content-Type"content="text/html;charset=ISO-8859-
1">
<linkrel="stylesheet"

href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<title>Products</title>
</head>
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1>Products</h1>
<p>Alltheavailableproductsinourstore</p>
</div>
</div>
</section>
<sectionclass="container">
<divclass="row">
<divclass="col-sm-6col-md-3"style="padding-bottom:15px">
<divclass="thumbnail">
<divclass="caption">
<h3>${product.name}</h3>
<p>${product.description}</p>
<p>${product.unitPrice}USD</p>
<p>Available${product.unitsInStock}unitsinstock</p>
</div>
</div>
</div>
</div>
</section>
</body>
</html>
4. Finally,runtheapplicationandentertheURL
http://localhost:8080/webstore/products.Youwillbeabletoseeawebpage
displayingtheproductinformationasshowninthefollowingscreenshot:
TheProductspagedisplayingtheproductinformation
Whatjusthappened?
Ouraimistoshowthedetailsofaproductonourwebpage;thus,inordertodothis,we
firstneedadomainobjecttoholdthedetailsoftheproduct.That’swhatwedidinstep1;
wejustcreatedaclasscalledProduct(Product.java)tostoreinformationaboutthe
product,suchasthename,description,price,andsoon.
AswehavealreadylearnedfromtheAnoverviewoftheSpringMVCrequestflowsection,
toshowanydynamicdataonawebpage,priortothis,weneedtoputthisdatainamodel;
onlythenwilltheviewbeabletoreadthisdatafromthemodelandrenderitontheweb
page.So,toputtheproductinformationinamodel,wejustcreatedonemorecontroller
calledProductController(ProductController.java)instep3.
IntheProductControllerclass,wejusthaveasinglemethodcalledlistwhose
responsibilityistocreateaproductdomainobjecttoholdtheinformationabouttheApple
iPhone5sandaddthatobjecttothemodel.Andfinally,wereturntheviewnameas
products.That’swhatweweredoingthroughthefollowinglinesinthelistmethodof
ProductController:
model.addAttribute("product",iphone);
return"products";
SinceweconfiguredInternalResourceViewResolverasourviewresolverintheweb
applicationcontextconfigurationfile,intheprocessofresolvingtheviewfileforthe
givenviewname(inourcase,theviewnameisproducts),theviewresolverwilltryto
lookforafileproducts.jspunder/WEB-INF/views/.That’swhy,wecreated
products.jspinstep4.Ifyouskipstep4,youwillgettheHTTPStatus404errorwhen
runningtheproject.
Forabettervisualexperience,products.jspcontainslotsofdivtagswithBootstrapCSS
stylesapplied(BootstrapisanopensourceCSSframework),sodon’tthinkthat
products.jspisverycomplex;asamatteroffact,itisverysimple.Youneednotbother
aboutthedivtags.Thesearepresentjustfortheappeal.Youonlyneedtoobservethe
followingfourtagscarefullyinproducts.jsptounderstanddataretrievalfromthemodel:
<h3>${product.name}</h3>
<p>${product.description}</p>
<p>${product.unitPrice}USD</p>
<p>Available${product.unitsInStock}unitsinstock</p>
Notethe${product.unitPrice}expressioncarefully;thetextproductintheexpression
isthenameofthekeythatweusedtostoretheiphoneobjectinthemodel.(Remember
thislinemodel.addAttribute("product",iphone);fromtheProductController
class.)ThetextunitPriceisnothingbutoneofthefieldsfromtheProductdomainclass
(Product.java).Similarly,weshowsomeimportantfieldsoftheproductdomainclassin
theproducts.jspfile.
Tip
WhenIsaythatpriceisthefieldname,Iamactuallymakinganassumptionherethatyou
havefollowedthestandardJavabeannamingconventionsforthegettersandsettersof
yourdomainclass.
Thisisbecause,whenSpringevaluatestheexpression${product.unitPrice},itis
actuallytryingtocallthegettermethodofthefieldtogetthevalue,soitwillexpecta
getUnitPrice()methodintheProduct.javafile.
Aftercompletingstep4,ifwerunourapplicationandentertheURL
http://localhost:8080/WebStore/products,wewillbeabletoseeawebpage
displayingtheproductinformationasshowninthepreviousscreenshot.
So,wehavecreatedadomainclasstoholdinformationaboutaproduct,createdasingle
productobjectinthecontroller,andaddedittothemodel.Finally,weshowedtheproduct
informationintheview.
Thepersistencelayer
Sincewehadasingleproduct,wejustinstantiateditinthecontrolleritselfanddisplayed
thisproductinformationonourwebpagesuccessfully.However,atypicalwebstore
containsthousandsofproducts;alltheinformationfortheseproductsisusuallystoredina
database.So,weneedtomakeourProductControllerclasssmartenoughtoloadallthe
productinformationfromthedatabaseintothemodel.However,ifwewriteallthedata
retrievallogicintheProductControllerclassitselftoretrieveproductinformationfrom
thedatabase,ourProductControllerclasswillblowdownintoabigchunkoffile.
Logicallyspeaking,dataretrievalisnotthedutyofthecontrollerbecausethecontrolleris
apresentationlayercomponent.Moreover,weneedtoorganizedataretrievalcodeina
separatelayersothatwecanreusethislogicasmuchaspossiblefromothercontrollers
andlayers.
HowdoweretrievedatafromthedatabasetheSpringMVCway?Therecomesthe
conceptofthepersistencelayer.Apersistencelayerusuallycontainsrepositoryobjectsto
accessdomainobjects.Arepositoryobjectmakesqueriestothedatasourceforthedata,
thereaftermapsthedatafromthedatasourcetoadomainobject,andfinally,persiststhe
changesinthedomainobjecttothedatasource.So,arepositoryobjectistypically
responsibleforCRUDoperations(Create,Read,Update,andDelete)ondomainobjects.
The@Repositoryannotation(org.springframework.stereotype.Repository)isan
annotationthatmarksaspecificclassasarepository.The@Repositoryannotationalso
indicatesthattheSQLexceptionsthrownfromtherepositoryobject’smethodsshouldbe
translatedintoSpring’sDataAccessExceptions.Let’screatearepositorylayerforour
application.
Timeforaction–creatingarepository
object
Performthefollowingstepstocreatearepositoryclasstoaccessyourproductdomain
objects:
1. CreateaninterfacecalledProductRepositoryunderthepackage
com.packt.webstore.domain.repositoryinthesourcefoldersrc/main/java.Add
asinglemethoddeclarationinit,asfollows:
List<Product>getAllProducts();
2. CreateaclasscalledInMemoryProductRepositoryunderthepackage
com.packt.webstore.domain.repository.implinthesourcefolder
src/main/java.Now,addthefollowingcodeintoit:
packagecom.packt.webstore.domain.repository.impl;
importjava.math.BigDecimal;
importjava.util.ArrayList;
importjava.util.List;
importorg.springframework.stereotype.Repository;
importcom.packt.webstore.domain.Product;
importcom.packt.webstore.domain.repository.ProductRepository;
@Repository
publicclassInMemoryProductRepositoryimplementsProductRepository{

privateList<Product>listOfProducts=newArrayList<Product>();

publicInMemoryProductRepository(){
Productiphone=newProduct("P1234","iPhone5s",new
BigDecimal(500));
iphone.setDescription("AppleiPhone5ssmartphonewith4.00-inch
640x1136displayand8-megapixelrearcamera");
iphone.setCategory("SmartPhone");
iphone.setManufacturer("Apple");
iphone.setUnitsInStock(1000);

Productlaptop_dell=newProduct("P1235","DellInspiron",new
BigDecimal(700));
laptop_dell.setDescription("DellInspiron14-inchLaptop(Black)
with3rdGenerationIntelCoreprocessors");
laptop_dell.setCategory("Laptop");
laptop_dell.setManufacturer("Dell");
laptop_dell.setUnitsInStock(1000);

Producttablet_Nexus=newProduct("P1236","Nexus7",new
BigDecimal(300));
tablet_Nexus.setDescription("GoogleNexus7isthelightest7inch
tabletWithaquad-coreQualcommSnapdragon™S4Proprocessor");
tablet_Nexus.setCategory("Tablet");
tablet_Nexus.setManufacturer("Google");
tablet_Nexus.setUnitsInStock(1000);

listOfProducts.add(iphone);
listOfProducts.add(laptop_dell);
listOfProducts.add(tablet_Nexus);
}
publicList<Product>getAllProducts(){
returnlistOfProducts;
}
}
3. OpenProductControllerfromthepackagecom.packt.webstore.controllerin
thesourcefoldersrc/main/java,andaddaprivatereferencetoProductRepository
withthe@Autowiredannotation
(org.springframework.beans.factory.annotation.Autowired),asfollows:
@Autowired
privateProductRepositoryproductRepository;
4. Now,alterthebodyofthelistmethod,asfollows,inProductController:
@RequestMapping("/products")
publicStringlist(Modelmodel){
model.addAttribute("products",productRepository.getAllProducts());
return"products";
}
5. Then,opentheviewfileproducts.jspfromsrc/main/webapp/WEB-INF/views/,
andremovealloftheexistingcodeandreplaceitwiththefollowingcodesnippet:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<head>
<metahttp-equiv="Content-Type"content="text/html;charset=ISO-
8859-1">
<linkrel="stylesheet"

href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<title>Products</title>
</head>
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1>Products</h1>
<p>Alltheavailableproductsinourstore</p>
</div>
</div>
</section>
<sectionclass="container">
<divclass="row">
<c:forEachitems="${products}"var="product">
<divclass="col-sm-6col-md-3"style="padding-bottom:15px">
<divclass="thumbnail">
<divclass="caption">
<h3>${product.name}</h3>
<p>${product.description}</p>
<p>$${product.unitPrice}</p>
<p>Available${product.unitsInStock}unitsinstock</p>
</div>
</div>
</div>
</c:forEach>
</div>
</section>
</body>
</html>
6. Finally,runtheapplicationandentertheURL
http://localhost:8080/webstore/products.Youwillseeawebpagedisplaying
theproductinformationasshowninthefollowingscreenshot:
TheProductspagedisplayingalloftheproductinformationfromthein-memory
repository
Whatjusthappened?
Sincewedon’twanttowriteallofthedataretrievallogicinsideProductController
itself,wedelegatedthistasktoanotherclasscalledInMemoryProductRepository.The
InMemoryProductRepositoryclasshasasinglemethodcalledgetAllProducts(),which
returnsalistofproductdomainobjects.
Asthenameimplies,InMemoryProductRepositoryisjustadummy,in-memoryproduct
repository.Itdoesnotretrieveanyrealproductdomainobjectinformationfromany
databaseassuch;rather,itjustinstantiatesalistofproductdomainobjectsinits
constructor.So,instep2,wejustcreatedtheInMemoryProductRepositoryclass,addeda
singlemethodgetAllProducts()toit,andinstantiatedsomeproductsintheconstructor.
Youmaywonder,then,whatwedidinstep1.Instep1,wejustcreatedaninterfacecalled
ProductRepository,whichdefinestheexpectedbehaviorofaproductrepository.Asof
now,theonlyexpectedbehaviorofaProductRepositoryinterfaceistoreturnalistof
productdomainobjects(getAllProducts),andourInMemoryProductRepositoryclassis
justanimplementationofthisinterface.
Writingrealdataretrievalcodeisbeyondthescopeofthisbook,soIhavecreated
InMemoryProductRepositoryjustfordemonstrationpurposes.However,itispossibleto
replacetheInMemoryProductRepositoryclasswithanyotherrealimplementationthat
canretrieverealdatafromthedatabase.
Whydowehaveaninterfaceandanimplementationfortheproductrepository?
Rememberthatweareactuallycreatingapersistencelayerforourapplication.Whois
goingtouseourpersistencelayerrepositoryobject?Itwillpossiblybeusedbya
controllerobject(inourcase,ProductController)fromthecontrollerlayer,soitisnot
thebestpracticetoconnecttwolayers(controllerandpersistence)withadirectreference.
Instead,wecan,infuture,haveaninterfacereferenceinthecontrollersothatwecan
easilyswitchtodifferentimplementationsoftherepositorywithoutdoinganycode
changesinthecontrollerclass,ifwewant.
That’sthereasonwhywehadtheProductRepositoryreferenceinour
ProductControllerclassinstep3,andnottheInMemoryProductRepositoryclass
reference.NotethefollowinglinesinProductController:
@Autowired
privateProductRepositoryproductRepository;
Whatistheneedofthe@Autowiredannotationhere?Ifyouobservethe
ProductControllerclasscarefully,youmaywonderwhywedidn’tinstantiateanyobject
forthereference,productRepository.Nowherecouldweseeasinglelinesaying
somethinglikeproductRepository=newInMemoryProductRepository();.
SohowcometheexecutionofthelineproductRepository.getAllProducts()worksjust
finewithoutanyNullPointerExceptionerrorinthelistmethodofthe
ProductControllerclass?
model.addAttribute("products",productRepository.getAllProducts());
WhoassignstheInMemoryProductRepositoryobjecttotheproductRepository
reference?TheansweristhattheSpringFrameworkassignsthe
InMemoryProductRepositoryobjecttotheproductRepositoryreference.
RememberwelearnedthatSpringcreatesandmanagesbeans(objects)forevery
@controllerclass?Similarly,Springcreatesandmanagesbeansfor@Repositoryclasses
aswell.AssoonasSpringseesthe@Autowiredannotationontopofthe
ProductRepositoryreference,itassignstheobjectofInMemoryProductRepositoryto
thisreferencesinceSpringalreadycreatedandholdstheInMemoryProductRepository
objectinitsobjectcontainer(thewebapplicationcontext).
Ifyouremember,weconfiguredacomponentscanthroughthefollowingtagintheweb
applicationcontextconfigurationfile:
<context:component-scanbase-package="com.packt.webstore"/>
Also,welearnedearlierthatifweconfigureourwebapplicationcontextasmentioned,it
notonlydetectscontrollers(@controller),butitalsodetectsotherstereotypessuchas
repositories(@Repository)andservices(@Service).
Sinceweaddedthe@RepositoryannotationontopoftheInMemoryProductRepository
class,SpringknowsthatifanyreferenceofthetypeproductRepositoryhasan
@Autowiredannotationontopofit,thenitshouldassigntheimplementationobject
InMemoryProductRepositorytothatreference.Thisprocessofmanagingthedependency
betweenclassesiscalleddependencyinjectionorwiringintheSpringworld.So,tomark
anyclassasarepositoryobject,weneedtoannotatethatclasswiththe@Repository
annotation(org.springframework.stereotype.Repository).
Weunderstandhowthepersistencelayerworks,butaftertherepositoryobjectreturnsa
listofproducts,howdoweshowitonthewebpage?Ifyourememberhowweaddedour
firstproducttothemodel,itisverysimilartothat.Insteadofasingleobject,thistimewe
addalistofobjectstothemodelthroughthefollowinglineinthelistmethodof
ProductController:
model.addAttribute("products",productRepository.getAllProducts());
Intheprecedingcode,productRepository.getAllProducts()justreturnsalistof
productdomainobjects(List<Product>),andwedirectlyaddthislisttothemodel.
Inthecorrespondingviewfile(products.jsp),usingthe<C:forEach>tag,weloop
throughthelistanddisplaytheinformationforeachproductinsideastyleddivtag:
<c:forEachitems="${products}"var="product">
<divclass="col-sm-6col-md-3"style="padding-bottom:15px">
<divclass="thumbnail">
<divclass="caption">
<h3>${product.name}</h3>
<p>${product.description}</p>
<p>${product.unitPrice}USD</p>
<p>Available${product.unitsInStock}unitsinstock</p>
</div>
</div>
</div>
</c:forEach>
Again,notethatthetextproductsintheexpression${products}isnothingbutthekey
thatweusedwhenaddingtheproductlisttothemodelfromtheProductController
class.
TheforeachloopisaspecialJSTLloopingtagthatwillrunthroughthelistofproducts
andassigneachproducttoavariablecalledproduct(var="product")oneachiteration.
Fromtheproductvariable,wefetchinformationsuchasthename,description,and
unitPriceoftheproductanddisplayitwithinthe<h3>and<p>tags.That’showweare
finallyabletoseethelistofproductsontheproductswebpage.
Theservicelayer
Sofarsogood;wecreatedapresentationlayerthatcontainsacontroller,dispatcher
servlet,viewresolvers,andsoon.Then,wecreatedadomainlayerthatcontainsasingle
domainclass,Product.Finally,wecreatedthepersistencelayer,whichcontainsa
repositoryinterfaceandanimplementationtoaccessourProductdomainobjects.
However,wearestillmissingonemoreconceptcalledtheservicelayer.Whydoweneed
theservicelayer?Wesawhowapersistencelayerdealswithallofthelogicrelatedtodata
access(CRUD)andthepresentationlayerdealswithalloftheactivitiesrelatedtotheweb
requestandview;thedomainlayercontainsclassestoholdinformationthatisretrieved
fromdatabaserecords/thepersistencelayer.However,wherecanweputthecodefor
businessoperations?
TheservicelayerexposesbusinessoperationsthatcouldbecomposedofmultipleCRUD
operations.TheseCRUDoperationsareusuallyperformedbytherepositoryobjects.For
example,youcouldhaveabusinessoperationtoprocessacustomerorder,andinorderto
performsuchabusinessoperation,youwouldneedtoperformthefollowingoperations:
1. First,ensurethatalloftheproductsintherequestedorderareavailableinyourstore.
2. Second,haveasufficientquantityoftheseproductsinyourstore.
3. Finally,updatetheproductinventorybyreducingtheavailablecountforeach
productthatwasordered.
Serviceobjectsaregoodcandidatesforsuchbusinessoperationslogic.Theservice
operationscouldalsorepresenttheboundariesofSQLtransactions;thismeansthatallof
theelementaryCRUDoperationsperformedinsidethebusinessoperationshouldbeinside
atransaction:eitherallofthemshouldsucceedortheyshouldrollbackincaseoferror.
Timeforaction–creatingaserviceobject
Performthefollowingstepstocreateaserviceobjectthatwillperformthesimplebusiness
operationoforderprocessing:
1. OpentheinterfaceProductRepositoryfromthepackage
com.packt.webstore.domain.repositoryinthesourcefoldersrc/main/java,and
addonemoremethoddeclarationonit,asfollows:
ProductgetProductById(StringproductID);
2. OpentheimplementationclassInMemoryProductRepositoryandaddan
implantationforthepreviouslydeclaredmethod,asfollows:
publicProductgetProductById(StringproductId){
ProductproductById=null;

for(Productproduct:listOfProducts){
if(product!=null&&product.getProductId()!=null&&
product.getProductId().equals(productId)){
productById=product;
break;
}
}

if(productById==null){
thrownewIllegalArgumentException("Noproductsfoundwiththe
productid:"+productId);
}

returnproductById;
}
3. CreateaninterfacecalledOrderServiceunderthepackage
com.packt.webstore.serviceinthesourcefoldersrc/main/java.Now,adda
methoddeclarationinitasfollows:
voidprocessOrder(StringproductId,intcount);
4. CreateaclasscalledOrderServiceImplunderthepackage
com.packt.webstore.service.implinthesourcefoldersrc/main/java.Then,add
thefollowingcodeintoit:
packagecom.packt.webstore.service.impl;
importorg.springframework.beans.factory.annotation.Autowired;
importorg.springframework.stereotype.Service;
importcom.packt.webstore.domain.Product;
importcom.packt.webstore.domain.repository.ProductRepository;
importcom.packt.webstore.service.OrderService;
@Service
publicclassOrderServiceImplimplementsOrderService{
@Autowired
privateProductRepositoryproductRepository;

publicvoidprocessOrder(StringproductId,longquantity){
ProductproductById=productRepository.getProductById(productId);

if(productById.getUnitsInStock()<quantity){
thrownewIllegalArgumentException("OutofStock.AvailableUnits
instock"+productById.getUnitsInStock());
}

productById.setUnitsInStock(productById.getUnitsInStock()-
quantity);
}
}
5. Now,createonemorecontrollerclasscalledOrderControllerunderthepackage
com.packt.webstore.controllerinthesourcefoldersrc/main/java,andaddthe
followingcodeintoit:
packagecom.packt.webstore.controller;
importorg.springframework.beans.factory.annotation.Autowired;
importorg.springframework.stereotype.Controller;
importorg.springframework.ui.Model;
importorg.springframework.web.bind.annotation.RequestMapping;
importcom.packt.webstore.service.OrderService;
@Controller
publicclassOrderController{

@Autowired
privateOrderServiceorderService;
@RequestMapping("/order/P1234/2")
publicStringprocess(){
orderService.processOrder("P1234",2);
return"redirect:/products";
}
}
6. Finally,runtheapplicationandentertheURL
http://localhost:8080/webstore/order/P1234/2.Youwillbeabletoseeaweb
pagedisplayingtheproductinformationasshowninthefollowingscreenshot(note
thattheavailableunitsinstockforiPhone5sshowasAvailable998unitsinstock):
TheProductspagedisplayingtheproductinformationafterthestockwasupdated
viaaservicecall
Whatjusthappened?
Beforegoingthroughthesteps,Ijustwanttoremindyouofafactregardingrepository
objects:allofthedataaccess(CRUD)operationsonadomainobjectshouldbecarried
throughrepositoryobjectsonly.Factnumbertwoisthatserviceobjectsrelyonrepository
objectstocarryoutalloperationsrelatedtodataaccess.That’swhy,beforecreatingthe
actualserviceinterface/implementation,wecreatedarepositoryinterface/
implementationmethod(getProductById)insteps1and2.
ThegetProductByIdmethodfromtheInMemoryProductRepositoryclassjustreturnsa
productdomainobjectforthegivenproductID.Weneedthismethodwhenwewritethe
logicforourserviceobjectmethod(processOrder)intheOrderServiceImplclass.Ifthe
productisnotfoundforthegivenID,thenInMemoryProductRepositorythrows
IllegalArgumentException.
Now,let’sreviewsteps3and4,wherewecreatedtheactualservicedefinitionand
implementation.Instep3,wecreatedaninterfacecalledOrderServicetodefineallofthe
expectedresponsibilityofanorderservice.Wedefinedonlyoneresponsibility,asofnow,
withinthatinterface;thatis,toprocesstheorderviathemethod,processOrder.The
processOrdermethodhastwoparameters:oneisproductIdandtheotherisquantity.In
step4,weimplementedtheprocessOrdermethodwithintheOrderServiceImplclass,
wherewereducedtheamountofstockavailableforthegivenproductIdbythequantity
parameter.
Inthepreviousexercise,withintheProductControllerclass,weconnectedcontroller
andrepositorythroughtheProductRepositoryinterfacereferencetomaximizeloose
coupling.Similarly,wehavenowconnectedtheservicelayerandrepositorylayerthrough
theProductRepositoryinterfacereference,asfollows,intheOrderServiceImplclass:
@Autowired
privateProductRepositoryproductRepository;
Aswehavealreadylearned,SpringassignedtheInMemoryProductRepositoryobjectto
theproductRepositoryreferenceinthepreviouslymentionedcodebecausethe
productRepositoryreferencehasthe@Autowiredannotation,andweknowthatSpring
createsandmanagesallofthe@Serviceand@Repositoryobjects.Notethat
OrderServiceImplhasthe@Serviceannotation
(org.springframework.stereotype.Service)ontopofit.Weusedthe
productRepositoryreferencetogettheproductforthegivenIDwithintheprocessOrder
methodoftheOrderServiceImplclassasfollows:
publicvoidprocessOrder(StringproductId,longquantity){
ProductproductById=productRepository.getProductById(productId);

if(productById.getUnitsInStock()<quantity){
thrownewIllegalArgumentException("OutofStock.AvailableUnitsin
stock"+productById.getUnitsInStock());
}

productById.setUnitsInStock(productById.getUnitsInStock()-quantity);
}
Tip
Toensuretransactionalbehavior,Springprovidesthe@Transactionalannotation
(org.springframework.transaction.annotation.Transactional).Weneedtoannotate
servicemethodswiththe@Transactionalannotationtodefinetransactionattributes,and
weneedtodosomemoreconfigurationinourapplicationcontextfortransactional
behaviortotakeeffect.
However,sinceweareusingdummy,in-memoryrepositoriestomimicdataaccess,to
annotateservicemethodswiththe@Transactionalannotationismeaningless.Toknow
moreabouttransactionmanagementinSpring,referto
http://docs.spring.io/spring/docs/current/spring-framework-
reference/html/transaction.html.
Wealreadycreatedtheservicelayer,andnowitisreadytobeconsumedfromthe
presentationlayer.Itistimeforustoconnectourservicelayerwiththecontroller.Instep
5,wecreatedonemorecontroller,OrderController,witharequestmappingmethod
calledprocessinitthatisshowninthefollowingcodesnippet:
@RequestMapping("/order/P1234/2")
publicStringprocess(){
orderService.processOrder("P1234",2);
return"redirect:/products";
}
TheprocessmethodfromtheOrderControllerclassusesourorderServicereferenceto
processtheorderfortheproductID,P1234.Aftersuccessfullyexecutingtheprocess
methodofOrderController,theavailableunitsinstockshouldgetreducedby2forthe
productwiththeID,P1234.
Youwillalsonoticethatwemappedthe/order/P1234/2URLpathtotheprocess
methodusingthe@RequestMappingannotation.So,whenwefinallytrytohittheURL
http://localhost:8080/webshop/order/P1234/2,wewillbeabletoseethatthe
availableunitsinstockgetreducedbytwofortheproduct,P1234.
Haveagohero–accessingtheproductdomain
objectviaaservice
InourProductControllerclass,weonlyhavetheProductRepositoryreferenceto
accesstheProductdomainobject.However,toaccessProductRepositorydirectlyfrom
ProductControllerisnotthebestpractice;itisalwaysgoodtoaccessthepersistence
layerrepositoryviatheserviceobject.However,wehavenotcreatedanyserviceobjectto
mediatebetweenProductControllerandProductRepository.
Whydon’tyoucreateaservicelayertomediatebetweenProductControllerand
ProductRepository?Thefollowingaresomeofthethingsyoucantryout:
1. CreateaninterfacecalledProductServicewithamethoddeclaration,List
<Products>getAllProducts();.
2. Createanimplementationclass,ProductServiceImpl,fortheProductService
interface.
3. AutowiretheProductRepositoryreferenceintheProductServiceImplclassand
usethisreferencewithinthegetAllProductsmethodtogetalloftheproductsfrom
ProductRepository.
4. ReplacetheProductRepositoryreferencewiththeProductServicereferenceinthe
ProductControllerclass.Accordingly,changethelistmethodinthe
ProductControllerclass.
5. Afterfinishingthis,youwillbeabletoseethesameproductlistingsundertheURL,
http://localhost:8080/webshop/products/.
Anoverviewofthewebapplication
architecture
Sofar,wehaveseenhowtoorganizeourcodeintolayerssothatwecanavoidtight
couplingbetweenvariouscodefiles,andimprovereusabilityandtheseparationof
concerns.Wejustcreatedonedomainclass,onerepositoryclass,andoneserviceclassfor
demonstrationpurposes,butatypical,real-worldMVCapplicationmaycontainasmany
domain,repository,andserviceclassesasrequired.Eachlayerisusuallyconnected
throughinterfacesandalwayscontrolleraccessdomainobjectsfromtherepositoryviathe
serviceinterfaceonly.
Everytypical,enterprise-levelSpringMVCapplicationwilllogicallyhavefourlayers:
presentation,domains,persistence,andservices.Thedomainlayerissometimescalledthe
modellayer.Thefollowingblockdiagramwillhelpyouconceptualizethisidea:
ThelayersofaSpringMVCapplication
So,welearnedhowtocreateaservicelayerobjectandrepositorylayerobject;whatwe
sawintheservicelayerandrepositorylayerwasjustaglimpse.Springhasextensive
supporttodealwithdatabasesandtransactions;handlingtheseisaveryvasttopicand
deservesitsownbook.Intheupcomingchapters,wewillconcentratemoreonthe
presentationlayer,whichcontainsmostoftheconceptsrelatedtoSpringMVCratherthan
thoserelatedtothedatabaseandtransaction.
Haveagohero–listingallourcustomers
ItisgreatthatyouhavelistedalloftheproductsinyourwebapplicationundertheURL,
http://localhost:8080/webstore/products,butinordertobecomeasuccessfulweb
store,maintainingonlytheproductinformationisnotenough.Youneedtomaintain
informationaboutthecustomeraswellsothatyoucanattractthembygivingspecial
discountsbasedontheirpurchasehistory.
Whydon’tyoumaintaincustomerinformationinyourapplication?Executethefollowing
stepstomakesomeimprovementstoyourapplicationtomaintaincustomerinformation:
1. AddonemoredomainclasscalledtheCustomerdomainclassinthesamepackage
wheretheproductexists.
2. AddfieldssuchascustomerId,name,address,andnoOfOrdersMadetotheCustomer
class.
3. Createapersistencelayertoreturnallcustomers.
4. CreateaninterfacecalledCustomerRepositorywithamethoddeclaration,List
<Customers>getAllCustomers();.
5. CreateanimplementationInMemoryCustomerRepositoryforCustomerRepository
andinstantiateadummycustomerintheconstructorof
InMemoryCustomerRepository,asyoudidforInMemoryProductRepository.
6. Createaservicelayertogetallofthecustomersfromtherepository.
7. CreateaninterfacecalledCustomerServicewithamethoddeclaration,List
<Customers>getAllCustomers().
8. CreateanimplementationCustomerServiceImplforCustomerService.
9. CreateonemorecontrollercalledCustomerController.
10. AddarequestmappingmethodtomaptheURL,
http://localhost:8080/webstore/customers.
11. Createaviewfilecalledcustomers.jsp.
Afterfinishingthisexercise,youwillbeabletoseeallofyourcustomersundertheURL,
http://localhost:8080/webstore/customers.Thisisverysimilartothewaywelisted
allofourproductsundertheURL,http://localhost:8080/webstore/products.
Summary
Atthestartofthischapter,welearnedthedutyofadispatcherservletandhowitmapsa
requestusingthe@RequestMappingannotation.Next,wesawwhatawebapplication
contextisandhowtoconfigureitforourwebapplication.Afterthat,wegotalittle
introductionaboutviewresolversandhowInternalResourceViewResolverresolvesthe
viewfileforthegivenlogicalviewname.WealsolearnedtheconceptofMVCandthe
overallrequestflowofaSpringMVCapplication,andthenwelearnedaboutweb
applicationarchitecture.Inthewebapplicationarchitecturesection,wesawhowtocreate
andorganizecodeunderthevariouslayersofaSpringMVCapplication,suchasthe
domainlayer,persistencelayer,andservicelayer.Atthesametime,wesawhowto
retrieveproductdomainobjectsfromtherepositoryandpresentthemonthewebpage
usingthecontroller.Wealsolearnedwhereaserviceobjectfitsin.Finally,wesawan
overviewofthewebapplicationarchitecture.
IhopeyougotagoodoverviewofSpringMVCandthevariouscomponentsinvolvedin
developingaSpringMVCapplication.Inthenextchapter,wearespecificallygoingto
learnmoreaboutcontrollersandrelatedconcepts.Meetyouinthenextchapter!
Chapter3.ControlYourStorewith
Controllers
InChapter2,SpringMVCArchitecture–ArchitectingYourWebStore,welearnedthe
overallarchitectureofaSpringMVCapplication.Wedidn’tgointoanyoftheconceptsin
detail;ourtotalaimwastounderstandtheoverallflow.Inthischapter,wearegoingto
haveanin-depthlookatthecontrollersinSpringMVCastheyhaveanimportantrole.
Thischapterwillcoverthefollowingconcepts:
Definingacontroller
URItemplatepatterns
Matrixvariables
Requestparameters
Definingacontroller
Controllersarepresentationlayercomponentsthatareresponsibleforrespondingtouser
actions.TheseactionscouldbeenteringaparticularURLonthebrowser,clickingona
link,submittingaformonawebpage,andsoon.AnyregularJavaclasscanbe
transformedintoacontrollerbysimplybeingannotatedwiththe@Controllerannotation
(org.springframework.stereotype.Controller).
Andwehadalreadylearnedthatthe@ControllerannotationsupportsSpring’s
autodetectionmechanismforauto-registeringthebeandefinitioninthewebapplication
context.Toenablesuchauto-registering,wemustaddthe<context:component-scan>tag
inthewebapplicationcontextconfigurationfile;wehaveseenhowtodothatintheThe
webapplicationcontextconfigurationsectionofChapter2,SpringMVCArchitecture–
ArchitectingYourWebStore.
Acontrollerclassismadeupofrequest-mappedmethods,alsocalledhandlermethods.
Handlermethodsareannotatedwiththe@RequestMappingannotation
(org.springframework.web.bind.annotation.RequestMapping).The@RequestMapping
annotationisusedtomapURLstoparticularhandlermethods.InChapter2,SpringMVC
Architecture–ArchitectingYourWebStore,wesawabriefintroductiononthe
@RequestMappingannotationandlearnedhowtoapplythe@RequestMappingannotation
onthehandlermethodlevel.However,inSpringMVC,wecanevenspecifythe
@RequestMappingannotationatthecontrollerclasslevel.Inthatcase,SpringMVCwill
considerthecontrollerclasslevel@RequestMappingannotationvaluebeforemappingthe
URLtothehandlermethods.Thisfeatureiscalledrelativerequestmapping.
Note
Thetermsrequestmappedmethod,mappedmethod,handlermethod,andcontroller
methodallmeanthesamething;thesetermsareusedtospecifythecontrollermethod
withan@RequestMappingannotation.Theyhavebeenusedinterchangeablyinthisbook.
Timeforaction–addingclass-level
requestmapping
Let’sadda@RequestMappingannotationonourProductControllerclasstodemonstrate
therelativerequestmappingfeature.However,beforethat,wejustwanttoensurethatyou
havealreadyreplacedtheProductRepositoryreferencewiththeProductService
referenceintheProductControllerclassaspartofthepreviouschapter’sTimeforaction
–creatingaserviceobjectsection.Becausecontactingthepersistencelayerdirectlyfrom
thepresentationlayerisnotabestpractice,allaccesstothepersistencelayershouldgo
throughtheservicelayer.Performthefollowingsteps(thosewhohavecompletedthis
exercisecandirectlystartfromstep5;otherspleasecontinuefromstep1):
1. CreateaninterfacecalledProductServiceunderthecom.packt.webstore.service
packageinsrc/main/javaandaddtwomethoddeclarationsinitasfollows:
List<Product>getAllProducts();
ProductgetProductById(StringproductID);
2. CreateaclasscalledProductServiceImplunderthe
com.packt.webstore.service.implpackageinsrc/main/javaandaddthe
followingcodeintoit:
packagecom.packt.webstore.service.impl;
importjava.util.List;
importorg.springframework.beans.factory.annotation.Autowired;
importorg.springframework.stereotype.Service;
importcom.packt.webstore.domain.Product;
importcom.packt.webstore.domain.repository.ProductRepository;
importcom.packt.webstore.service.ProductService;
@Service
publicclassProductServiceImplimplementsProductService{

@Autowired
privateProductRepositoryproductRepository;
publicList<Product>getAllProducts(){
returnproductRepository.getAllProducts();
}
publicProductgetProductById(StringproductID){
returnproductRepository.getProductById(productID);
}
}
3. OpenProductController,removetheexistingProductRepositoryreference,and
addtheProductServicereferenceasfollows:
@Autowired
privateProductServiceproductService;
4. Now,alterthebodyofthelistmethodintheProductControllerclassasfollows
(notethatthistimeweusedtheproductServicereferencetogetalloftheproducts):
@RequestMapping("/products")
publicStringlist(Modelmodel){
model.addAttribute("products",productService.getAllProducts());

return"products";
}
5. IntheProductControllerclass,addthefollowingannotationontopoftheclass:
@RequestMapping("/products")
6. Fromthelistmethod’s@RequestMappingannotation,removethevalueattribute
completely;sonow,thelistmethodwillhaveaplain@RequestMappingannotation
withoutanyattributesasfollows:
@RequestMapping
publicStringlist(Modelmodel){
7. Now,addonemorehandlermethodintheProductControllerclassasfollows:
@RequestMapping("/all")
publicStringallProducts(Modelmodel){
model.addAttribute("products",productService.getAllProducts());

return"products";
}
8. Finally,runtheapplicationagainandentertheURL
http://localhost:8080/webstore/products/allinthebrowsertoviewallofthe
products.
Whatjusthappened?
Whatwehavedemonstratedhereisasimpleconceptcalledrelativerequestmapping.We
didthefollowingthreethingsintheProductControllerclass:
Weaddedan@RequestMappingannotationattheclasslevelwithavalueattribute
definedas"/products"instep5
Weremovedthevalueattributefromthe@RequestMappingannotationofthelist
methodinstep6
Finally,weaddedonemorehandlermethodcalledallProducts,whichalsoputsthe
samelistofproductsonthemodelasthelistmethod,butunderadifferentURL
mapping—@RequestMapping("/all")
Inallourpreviousexamples,weannotatedthe@RequestMappingannotationsonlyatthe
controllermethodlevel,butSpringMVCalsoallowsustospecifyrequestmappingatthe
controllerclasslevel.Inthiscase,SpringMVCmapsaspecificURLpathatthemethod
levelthatisrelativetotheclasslevel@RequestMappingURLvalue.
Instep5,wejustaddedthe@RequestMappingannotationattheProductControllerclass
levelwiththeURLmappingvalue/products.Andinstep7,weaddedanewhandler
methodcalledallProductswithaURLmappingvalue/all.So,thefinalrequestpathfor
theallProductsmethodisformedbycombiningtheclassandmethodrequestmapping
values,whichis/products/all.So,ifwedefinedanyclasslevelrequestmapping,
SpringMVCwouldconsiderthatclasslevelrequestpathbeforemappingtherequestto
themethod.
Note
Steps1to4justteachyouhowtocreateandconnectaservicelayerobjectwiththe
ProductControllerclass.Asofnow,theProductServiceImplclassdoesnothaveany
distinguishablebusinesslogicinit;rather,itsimplydelegatesthecalltothepersistence
layer’srepositoryobject(ProductRepository)toaccesstheProductdomainobject.Soas
ofnow,thereisnorealmeaningtohaveaservicelayerforProductRepository;however,
infuture,ifwedecidetoreplacetheInMemoryProductRepositoryobjectwithareal
databasebackedrepositoryobject,wewilldefinitelyneedthisservicelayertowritecode
tohandletransaction-relatedtasks.So,justtomaintaintheindustry’sbestpractices,Ihave
retainedtheservicelayersinmostoftheexamplesinthisbook.
Instep6,wesimplydidn’tspecifyanyrequestpathvalueinthe@RequestMapping
annotationofthelistmethod.Bydoingso,wemadethelistmethodthedefaultrequest
mappingmethodfortheProductControllerclass.So,wheneverarequestURLendsup
withthecontrollerclasslevelrequestpathvaluewithoutanyfurtherrelativepath,Spring
MVCinvokesthismethodasaresponsetotherequest.
So,finallyinourcase,theURLhttp://localhost:8080/webstore/productswillbe
mappedtothelistmethodandhttp://localhost:8080/webstore/products/allwill
bemappedtotheallProductsmethod.
Note
Ifyouspecifymorethanonedefaultmappingmethodinsideacontroller,youwillget
IllegalStateExceptionwiththemessageAmbiguousmappingfound.So,acontroller
canhaveonlyonedefaultrequestmappingmethodatmost.
Popquiz–class-levelrequestmapping
Q1.Inawebapplicationcalledlibrarythathasthefollowingrequestmappingata
controllerclasslevelandinthemethodlevel,whichistheappropriaterequestURLto
maptherequesttothebooksmethod?
@RequestMapping("/books")
publicclassBookController{
...
@RequestMapping(value="/list")
publicStringbooks(Modelmodel){
...
1. http://localhost:8080/library/books/list
2. http://localhost:8080/library/list
3. http://localhost:8080/library/list/books
4. http://localhost:8080/library/
Q2.IfwehaveanotherhandlermethodcalledbookDetailsunderBookControlleras
follows,whatwilltheURLthatmapstothatmethodbe?
@RequestMapping()
publicStringbookDetails(Modelmodel){
...
1. http://localhost:8080/library/books/details
2. http://localhost:8080/library/books
3. http://localhost:8080/library/details
4. http://localhost:8080/library/
TheroleofacontrollerinSpringMVC
InSpringMVC,controllermethodsarethefinaldestinationpointthatawebrequestcan
reach.Afterbeinginvoked,thecontrollermethodstartstoprocessthewebrequestby
interactingwiththeservicelayertocompletetheworkthatneedstobedone.Usually,the
servicelayerexecutessomebusinessoperationsondomainobjectsandcallsthe
persistencelayertoupdatethedomainobjects.Aftertheprocessinghasbeencompleted
bytheservicelayerobject,thecontrollerisresponsibleforupdatingandbuildingupthe
modelobjectandchoosesaviewfortheusertoseenextasaresponse.
RememberthatSpringMVCalwayskeepsthecontrollersunawareofanyview
technologyused.That’swhythecontrollerreturnsonlyalogicalviewname;later,
DispatcherServletconsultswithViewResolvertofindouttheexactviewtobe
rendered.Accordingtothecontroller,ModelisacollectionofarbitraryobjectsandViewis
specifiedwithalogicalname.
Inallourpreviousexercises,thecontrollersusedtoreturnthelogicalviewnameand
updatethemodelviathemodelparameteravailableinthecontrollermethod.Thereis
another,seldomusedwayofupdatingthemodelandreturningtheviewnamefromthe
controllerwiththehelpoftheModelAndViewobject
(org.springframework.web.servlet.ModelAndView).Lookatthefollowingcode
snippet,forexample:
@RequestMapping("/all")
publicModelAndViewallProducts(){
ModelAndViewmodelAndView=newModelAndView();

modelAndView.addObject("products",productService.getAllProducts());
modelAndView.setViewName("products");
returnmodelAndView;
}
Theprecedingcodesnippetjustshowshowwecanencapsulatethemodelandviewusing
theModelAndViewobject.
Handlermapping
WehavelearnedthatDispatcherServletistheonethatdispatchestherequesttothe
handlermethodsbasedontherequestmapping;however,inordertointerpretthe
mappingsdefinedintherequestmapping,DispatcherServletneedsaHandlerMapping
implementation(org.springframework.web.servlet.HandlerMapping).The
DispatcherServletconsultswithoneormoreHandlerMappingimplementationstofind
outwhichcontroller(handler)canhandletherequest.So,HandlerMapping
determineswhichcontrollertocall.
TheHandlerMappinginterfaceprovidestheabstractionformappingrequeststohandlers.
TheHandlerMappingimplementationsarecapableofinspectingtherequestandcoming
upwithanappropriatecontroller.SpringMVCprovidesmanyHandlerMapping
implementations,andtheoneweareusingtodetectandinterpretmappingsfromthe
@RequestMappingannotationistheRequestMappingHandlerMappingclass
(org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping
TostartusingRequestMappingHandlerMapping,wehavetoaddthe<mvc:annotation-
driven>elementinourwebapplicationcontextconfigurationfilesothatSpringMVC
cancreateandregisterabeanforRequestMappingHandlerMappinginourwebapplication
context.Wealreadyconfigured<mvc:annotation-driven>inChapter2,SpringMVC
Architecture–ArchitectingYourWebStore,intheThewebapplicationcontext
configurationsection.
UsingURItemplatepatterns
Inthepreviouschapters,wesawhowtomapaparticularURLtoacontrollermethod;for
example,iftheURLenteredwashttp://localhost:8080/webstore/products,we
mappedthatrequesttothelistmethodofProductControllerandlistedalltheproduct
informationonthewebpage.
Whatifwewanttolistonlyasubsetoftheproductsbasedoncategory,forinstance,we
wanttodisplayonlytheproductsthatfallunderthecategoryoflaptopsiftheuserentered
theURLhttp://localhost:8080/webstore/products/laptop?Similarly,whatifthe
URLishttp://localhost:8080/webstore/products/tabletandwewouldliketoshow
onlytabletsonthewebpage?
Onewaytodothisistohaveaseparaterequestmappingmethodinthecontrollerfor
everyuniquecategory.However,itwon’tscaleifwehavehundredsofcategories;inthat
case,we’llhavetowriteahundredrequestmappingmethodsinthecontroller.Sohowdo
wedothisinanelegantway?
WeusetheSpringMVCURItemplatepatternfeature.IfyounotethefollowingURLs,
theonlypartthatchangesintheURListhecategorytype(laptopandtablet);otherthan
that,everythingremainsthesame:
http://localhost:8080/webstore/products/laptop
http://localhost:8080/webstore/products/tablet
So,wecandefineacommonURItemplateforthepreviouslymentionedURLs,which
mightlooklikehttp://localhost:8080/webstore/products/{category}.SpringMVC
canleveragethisfactandmakethattemplateportion({category})oftheURLavariable,
calledapathvariableintheSpringworld.
Timeforaction–showingproductsbased
oncategory
Let’saddacategoryviewtotheproductspageusingthepathvariable:
1. OpentheProductRepositoryinterfaceandaddonemoremethoddeclarationonits
getProductsByCategorymethod:
List<Product>getProductsByCategory(Stringcategory);
2. OpentheimplementationclassInMemoryProductRepositoryandaddan
implementationforthepreviouslydeclaredmethodasfollows:
publicList<Product>getProductsByCategory(Stringcategory){
List<Product>productsByCategory=newArrayList<Product>();

for(Productproduct:listOfProducts){
if(category.equalsIgnoreCase(product.getCategory())){
productsByCategory.add(product);
}
}

returnproductsByCategory;
}
3. Similarly,opentheProductServiceinterfaceandaddonemoremethoddeclaration
onitsgetProductsByCategorymethod:
List<Product>getProductsByCategory(Stringcategory);
4. OpentheserviceimplementationclassProductServiceImplandaddan
implementationasfollows:
publicList<Product>getProductsByCategory(Stringcategory){
returnproductRepository.getProductsByCategory(category);
}
5. OpentheProductControllerclassandaddonemorerequestmappingmethodas
follows:
@RequestMapping("/{category}")
publicStringgetProductsByCategory(Modelmodel,
@PathVariable("category")StringproductCategory){
model.addAttribute("products",
productService.getProductsByCategory(productCategory));
return"products";
}
6. RuntheapplicationandentertheURL
http://localhost:8080/webstore/products/tablet;youwillseesomethingas
specifiedinthefollowingscreenshot:
Showingproductsbycategorywiththehelpofpathvariables
Whatjusthappened?
Step5isthemostimportantinthewholesequencefromthepreviouslist,becauseallthe
stepspriortostep5aretheprerequisitesforstep5.Whatwearedoinginstep5isnothing
butaddingalistofproductobjectstothemodellikewenormallywould:
model.addAttribute("products",productService.getProductsByCategory(ProductC
ategory));
OnethingweneedtonotehereisthegetProductsByCategorymethodfrom
productService;weneedthismethodtogetthelistofproductsforthegivencategory,
andproductServiceassuchcannotgivethelistofproductsforthegivencategory.Itwill
asktherepository.That’swhy,instep4,weusedtheproductRepositoryreferencetoget
thelistofproductsbycategorywithintheProductServiceImplclass.Notethefollowing
codesnippetfromProductServiceImpl:
returnproductRepository.getProductsByCategory(category);
Anotherimportantthingtobenotedinthecodesnippetfromstep5isthe
@RequestMappingannotation’srequestpathvalueasfollows:
@RequestMapping("/{category}")
Byenclosingaportionofarequestpathwithincurlybraces,weindicatetotheSpring
MVCthatitisaURItemplatevariable.AccordingtoSpringMVCdocumentation,aURI
templateisaURI-likestringthatcontainsoneormorevariablenames.Whenyou
substitutevaluesforthesevariables,thetemplatebecomesaURI.
Forexample,theURItemplate
http://localhost:8080/webstore/products/{category}containsthevariable
category.Assigningthevaluelaptoptothevariableyields
http://localhost:8080/webstore/products/laptop.InSpringMVC,wecanusethe
@PathVariableannotation
(org.springframework.web.bind.annotation.PathVariable)toreadaURItemplate
variable.
Sincewehavethe@RequestMapping("/products")annotationattheProductController
level,theactualrequestpathofthegetProductsByCategorymethodwillbe
/products/{category}.Soatruntime,ifwegiveawebrequestURLas
http://localhost:8080/webstore/products/laptop,thenthecategorypathvariable
willhavethevaluelaptop.Similarly,forthewebrequest
http://localhost:8080/webstore/products/tablet,thecategorypathvariablewill
havethevaluetablet.
HowdoweretrievethevaluestoredintheURItemplatepathvariablecategory?Aswe
alreadymentioned,the@PathVariableannotationwillhelpusreadthatvariable.Allwe
needtodoissimplyannotatethegetProductsByCategorymethodparameterwiththe
@PathVariableannotationasfollows:
publicStringgetProductsByCategory(@PathVariable("category")String
productCategory,Modelmodel){
So,SpringMVCwillreadwhatevervalueispresentinthecategoryURItemplate
variableandassignittothemethodparameterproductCategory.So,wehavethe
categoryvalueinavariable,andwejustpassittoproductServicetogetthelistof
productsinthatcategory.Oncewegetthatlistofproducts,wesimplyaddittothemodel
andreturnthesameviewnamethatwehaveusedtolistalltheproducts.
Thevalueattributeinthe@PathVariableannotationshouldbethesameasthevariable
nameinthepathexpressionofthe@RequestMappingannotation.Forexample,ifthepath
expressionis"/products/{identity}",thentoretrievethepathvariableidentity,you
havetoformthe@PathVariableannotationas@PathVariable("identity").
Note
Ifthe@PathVariableannotationhasbeenspecifiedwithoutanyvalueattribute,itwilltry
toretrieveapathvariablewiththesamenameasthatofthevariablethatithasbeen
annotatedwith.
Forexample,ifyouspecifysimply@PathVariableStringproductId,thenSpringwill
assumethatitshouldlookforaURItemplatevariable"{productId}"intheURL.A
requestmappingmethodcanhaveanynumberof@PathVariableannotations.
Finally,instep6,whenweentertheURL
http://localhost:8080/webstore/products/tablet,weseeinformationabout
Google’sNexus7,whichisatablet.Similarly,ifweentertheURL
http://localhost:8080/webstore/products/laptop,weseeinformationaboutDell’s
Inspironlaptop.
Popquiz–requestpathvariable
Q1.InawebapplicationcalledWebStorethathasthefollowingrequestmappingata
controllerclasslevelandinthemethodlevel,whichistheappropriaterequestURLthat
canbeused?
@RequestMapping("/items")
publicclassProductController{
...
@RequestMapping(value="/type/{type}",method=RequestMethod.GET)
publicStringproductDetails(@PathVariable("type")StringproductType,
Modelmodel){
1. http://localhost:8080/WebStore/items/electronics
2. http://localhost:8080/WebStore/items/type/electronics
3. http://localhost:8080/WebStore/items/productType/electronics
4. http://localhost:8080/WebStore/type/electronics
Q2.Forthefollowingrequestmappingannotation,whicharethecorrectmethod
signaturestoretrievethepathvariables?
@RequestMapping(value="/manufacturer/{
manufacturerId}/product/{productId}")
1. publicStringproductByManufacturer(@PathVariableString
manufacturerId,@PathVariableStringproductId,Modelmodel)
2. publicStringproductByManufacturer(@PathVariableStringmanufacturer,
@PathVariableStringproduct,Modelmodel)
3. publicStringproductByManufacturer(@PathVariable("manufacturer")
StringmanufacturerId,@PathVariable("product")StringproductId,Model
model)
4. publicStringproductByManufacturer(@PathVariable("manufacturerId")
Stringmanufacturer,@PathVariable("productId")Stringproduct,Model
model)
Usingmatrixvariables
Inthelastsection,wesawtheURItemplatefacilitytobindvariablesintheURLrequest
path.However,thereisonemorewaytobindvariablesintherequestURLinaname-
valuepairstyle;theseboundvariablesarereferredtoasmatrixvariableswithinSpring
MVC.LookatthefollowingURL:
http://localhost:8080/webstore/products/filter/price;low=500;high=1000
InthisURL,theactualrequestpathisjustupto
http://localhost:8080/webstore/products/filter/price,afterwhichwehave
somethinglikelow=500;high=1000;here,lowandhigharejustmatrixvariables.
However,whatmakesmatrixvariablessospecialistheabilitytoassignmultiplevalues
forasinglevariable;thismeansthatwecanassignalistofvaluestoaURIvariable.Take
alookatthefollowingURL:
http://localhost:8080/webstore/products/filter/ByCriteria;brand=google,dell;category=tablet,laptop
InthegivenURL,wehavetwovariables,namely,brandandcategory;bothhave
multiplevalues,brand=google,dellandcategory=tablet,laptop.Howdoweread
thesevariablesfromtheURLduringrequestmapping?Weusethespecialbinding
annotation@MatrixVariable
(org.springframework.web.bind.annotation.MatrixVariable).Onecoolthingabout
the@MatrixVariableannotationisthatitallowsustocollectthematrixvariablesina
mapofcollections(Map<String,List<String>>),whichwillbemorehelpfulwhenwe
aredealingwithcomplexwebrequests.
Timeforaction–showingtheproducts
basedonfilter
Considerasituationwherewewanttofiltertheproductlistbasedonthebrandand
categoryvariables.Forexample,youwanttolistalltheproductsthatfallunderthe
categorylaptopandtabletsandfromthemanufacturersgoogleanddell.Withthehelp
ofthematrixvariables,wecanformaURLtobindthebrandandcategoryvariables’
valuesintotheURLasfollows:
http://localhost:8080/webstore/products/filter/ByCriteria;brand=google,dell;category=tablet,laptop
Let’smapthisURLtoahandlermethodwiththehelpofthe@MatrixVariableannotation:
1. OpentheProductRepositoryinterfaceandaddonemoremethoddeclaration,
getProductsByFilter,onit:
Set<Product>getProductsByFilter(Map<String,List<String>>
filterParams);
2. Opentheimplementationclass,InMemoryProductRepository,andaddthefollowing
methodimplementationforgetProductsByFilter:
publicSet<Product>getProductsByFilter(Map<String,List<String>>
filterParams){
Set<Product>productsByBrand=newHashSet<Product>();
Set<Product>productsByCategory=newHashSet<Product>();
Set<String>criterias=filterParams.keySet();

if(criterias.contains("brand")){
for(StringbrandName:filterParams.get("brand")){
for(Productproduct:listOfProducts){
if(brandName.equalsIgnoreCase(product.getManufacturer())){
productsByBrand.add(product);
}
}
}
}

if(criterias.contains("category")){
for(Stringcategory:filterParams.get("category")){

productsByCategory.addAll(this.getProductsByCategory(category));
}
}

productsByCategory.retainAll(productsByBrand);

returnproductsByCategory;
}
3. OpentheinterfaceProductServiceandaddonemoremethoddeclarationonit
calledgetProductsByFilterasfollows:
Set<Product>getProductsByFilter(Map<String,List<String>>
filterParams);
4. Opentheserviceimplementationclass,ProductServiceImpl,andaddthefollowing
methodimplementationforgetProductsByFilter:
publicSet<Product>getProductsByFilter(Map<String,List<String>>
filterParams){
returnproductRepository.getProductsByFilter(filterParams);
}
5. OpenProductControllerandaddonemorerequestmappingmethodasfollows:
@RequestMapping("/filter/{ByCriteria}")
publicStringgetProductsByFilter(@MatrixVariable(pathVar=
"ByCriteria")Map<String,List<String>>filterParams,Modelmodel){
model.addAttribute("products",
productService.getProductsByFilter(filterParams));
return"products";
}
6. Openthewebapplicationcontextconfigurationfile(DispatcherServlet-
context.xml)fromsrc/main/webapp/WEB-INF/spring/webcontext/andenable
matrixvariablesupportbysettingenable-matrix-variablestotrueinthe
<mvc:annotation-driven>tagasfollows:
<mvc:annotation-drivenenable-matrix-variables="true"/>
7. Finally,runtheapplicationandentertheURL
http://localhost:8080/webstore/products/filter/ByCriteria;brand=google,dell;category=tablet,laptop
youwillseetheproductlistingasshowninthefollowingscreenshot:
Usageofmatrixvariablesshowingproductlistfilteredbycriteria
Whatjusthappened?
OuraimistoretrievethematrixvariablevaluesfromtheURLanddosomethinguseful;
inourcase,theURLwearetryingtomapis
http://localhost:8080/webstore/products/filter/ByCriteria;brand=google,dell;category=tablet,laptop
wherewewanttoextractthematrixvariablesbrandandcategory.Thebrandand
categoryvariableshavethevaluesgoogle,dellandtablet,laptop,respectively.Inthe
previousURL,therequestpathisupto
http://localhost:8080/webstore/products/filter/ByCriteriaonly.That’swhy,in
step5,weannotatedourgetProductsByFilterrequestmappingmethodasfollows:
@RequestMapping("/filter/{ByCriteria}")
However,youmaywonderwhywehaveaURItemplate(/{ByCriteria})inthe
@RequestMappingannotation,whichislikemappingtoapathvariable.Itisbecauseifour
requestURLcontainsthematrixvariable,thenwewillhavetoformthe@RequestMapping
annotationwithaURItemplatetoidentifythestartingofmatrixvariable’ssegments
withinURL.That’swhywedefinedByCriteriaasaURItemplateintherequestmapping
annotation(@RequestMapping("/filter/{ByCriteria}")).
Note
AURLcanhavemultiplematrixvariables;eachmatrixvariablewillbeseparatedwitha;
(semicolon).Toassignmultiplevaluestoasinglevariable,eachvaluemustbeseparated
bya“,”(comma),orwecanrepeatthevariablename.SeethefollowingURL,whichisa
repeatedvariableversionofthesameURLthatweusedinourexample:
http://localhost:8080/webstore/products/filter/ByCategory;brand=google;brand=dell;category=tablet;category=laptop
NotethatwerepeatedthevariablesbrandandcategorytwiceintheURL.
WemappedthewebrequesttothegetProductsByFiltermethod,buthowdoweretrieve
thevaluefromthematrixvariables?Theansweristhe@MatrixVariableannotation.Itis
quitesimilartothe@PathVariableannotation;ifyounoticethegetProductsByFilter
methodsignatureinstep5,weannotatedthemethodparameterfilterParamswiththe
@MatrixVariableannotationasfollows:
publicStringgetProductsByFilter(@MatrixVariable(pathVar="ByCriteria")
Map<String,List<String>>filterParams,Modelmodel)
So,SpringMVCwillreadallthematrixvariablesfoundintheURLafterthe
{ByCriteria}URItemplateandplacethosematrixvariablesintothemapofthemethod
parameterfilterParams.ThefilterParamsmapwillhaveeachmatrixvariablenameas
keyandthecorrespondinglistwillcontainthemultiplevaluesassignedforthematrix
variable.ThepathVarattributefromthe@MatrixVariableannotationisusedtoidentify
thematrixvariablesegmentintheURL;that’swhyithasthevalueByCriteria,whichis
nothingbuttheURItemplatevaluethatweusedinourrequestmappingURL.
AURLcanhavemultiplematrixvariablesegments.TakealookatthefollowingURL:
http://localhost:8080/webstore/products/filter/ByCriteria;brand=google,dell;category=tablet,laptop/BySpecification;dimention=10,20,15;color=red,green,blue
Itcontainstwomatrixvariablesegments,eachidentifiedbytheprefixesByCriteriaand
BySpecification,respectively.Soinordertocaptureeachmatrixvariablesegmentintoa
map,wehavetoformthecontrollermethodsignatureasfollows:
@RequestMapping("/filter/{ByCriteria}/{BySpecification}")
publicStringfilter(@MatrixVariable(pathVar="ByCriteria")
Map<String,List<String>>criteriaFilter,@MatrixVariable(pathVar="
BySpecification")Map<String,List<String>>specFilter,Modelmodel){
WegotthevalueofthematrixvariablesintothemethodparameterfilterParams,but
whatdidwedowiththatfilterParamsmap?Wesimplypasseditasaparametertothe
servicemethodtoretrievetheproductsbasedoncriteriaasfollows:
productService.getProductsByFilter(filterParams)
Again,theservicepassesthatmaptotherepositorytogetthelistofproductsbasedonthe
criteria.Oncewegetthelist,wesimplyaddthatlisttothemodelandreturnthesame
viewnamethatwasusedtolisttheproducts.
ToenabletheuseofmatrixvariablesinSpringMVC,wesettheenable-matrix-
variablesattributeofthe<mvc:annotation-driven>tagtotrue;wedidthisinstep6.
Finally,wewereabletoviewtheproductsbasedonthespecifiedcriteriainstep7onour
productlistingpage.
Understandingrequestparameters
MatrixvariablesandpathvariablesareagreatwayofbindingvariablesintheURL
requestpath.However,thereisonemorewaytobindvariablesintheHTTPrequest,not
onlyasapartoftheURLbutalsointhebodyoftheHTTPwebrequest,whicharetheso-
calledHTTPparameters.YoumighthaveheardabouttheGETorPOSTparameters.GET
parametershavebeenusedforyearsasastandardwaytobindvariablesintheURL,and
POSTparametersareusedtobindvariablesinthebodyoftheHTTPrequest.Wewill
learnaboutPOSTparametersinthenextchapterduringformsubmission.
Okay,nowlet’sseehowtoreadGETrequestparametersusingtheSpringMVCstyle.To
demonstratetheuseoftherequestparameter,let’saddaproductdetailspagetoour
application.
Timeforaction–addingtheproduct
detailspage
Sofarinourproductlistingpage,wehaveonlyshownproductinformationsuchasthe
product’sname,description,price,andavailableunitsinstock.However,wehaven’t
showninformationsuchasthemanufacturer’sname,category,productID,andsoon.
Let’screateaproductdetailspagedisplayingthisinformationasfollows:
1. OpentheProductControllerclassandaddonemorerequestmappingmethodas
follows:
@RequestMapping("/product")
publicStringgetProductById(@RequestParam("id")StringproductId,
Modelmodel){
model.addAttribute("product",
productService.getProductById(productId));
return"product";
}
2. AddonemoreJSPviewfilecalledproduct.jspunderthedirectory
src/main/webapp/WEB-INF/views/,andaddthefollowingcodesnippetintoitand
saveit:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<head>
<metahttp-equiv="Content-Type"content="text/html;charset=ISO-8859-
1">
<linkrel="stylesheet"

href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<title>Products</title>
</head>
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1>Products</h1>
</div>
</div>
</section>
<sectionclass="container">
<divclass="row">
<divclass="col-md-5">
<h3>${product.name}</h3>
<p>${product.description}</p>
<p>
<strong>ItemCode:</strong><spanclass="labellabel-
warning">${product.productId}</span>
</p>
<p>
<strong>manufacturer</strong>:${product.manufacturer}
</p>
<p>
<strong>category</strong>:${product.category}
</p>
<p>
<strong>Availbleunitsinstock</strong>:
${product.unitsInStock}
</p>
<h4>${product.unitPrice}USD</h4>
<p>
<ahref="#"class="btnbtn-warningbtn-large"><span
class="glyphicon-shopping-cartglyphicon"></span>OrderNow
</a>
</p>
</div>
</div>
</section>
</body>
</html>
3. Now,runtheapplicationandentertheURL
http://localhost:8080/webstore/products/product?id=P1234;youwillseethe
productdetailspageasshowninthefollowingscreenshot:
Usageofrequestparametershowingproductdetailspage
Whatjusthappened?
Whatwedidinstep1isverysimilartowhatwedidinthegetProductsByCategory
methodofProductController.Wejustaddedaproductobjecttothemodelthatis
returnedbytheserviceobjectasfollows:
model.addAttribute("product",productService.getProductById(productId));
However,theimportantquestionhereis,whoisgivingthevalueoftheparameter
productId?Theanswerissimple,asyouguessed;sinceweannotatedtheparameter
productIdwiththe@RequestParam("id")annotation
(org.springframework.web.bind.annotation.RequestParam),SpringMVCwilltryto
readaGETrequestparameterwiththenameidfromtheURLandassignittothe
getProductByIdmethodparameter,productId.
The@RequestParamannotationalsofollowsthesameconventionforotherbinding
annotations;thatis,ifthenameoftheGETrequestparameterandthenameofthevariable
itisannotatedwitharethesame,thentherewillbenoneedtospecifythevalueattribute
inthe@RequestParamannotation.
Finally,instep6,weaddedonemoreviewfilecalledproduct.jspbecausewewanteda
detailedviewoftheproductsothatwecoulddisplayalltheinformationabouttheproduct.
Nothingfancyinthisproduct.jsp;asusual,wegetthevaluefromthemodelandshowit
withinHTMLtagsusingtheusualJSTLexpressionlanguagenotation${}asfollows:
<h3>${product.name}</h3>
<p>${product.description}</p>
......
WesawhowtoretrieveaGETrequestparameterfromtheURL,buthowdowepassmore
thanoneGETrequestparameterintheURL?Theansweristhatweneedtodelimiteach
parametervaluepairwithan&symbol;forexample,ifwewanttopasscategoryand
priceasGETrequestparametersinaURL,wehavetoformtheURLasfollows:
http://localhost:8080/WebStore/products/product?category=laptop&price=700
Similarly,tomaptheprecedingURLinarequestmappingmethod,ourrequestmapping
methodshouldhaveatleasttwoparameterswiththe@RequestParamannotation:
publicStringgetProducts(@RequestParamStringcategory,@RequestParam
Stringprice){
Popquiz–therequestparameter
Q1.WhichistheappropriaterequestURLforthefollowingrequestmappingmethod
signature?
@RequestMapping(value="/products",method=RequestMethod.GET)
publicStringproductDetails(@RequestParamStringrate,Modelmodel)
1. http://localhost:8080/webstore/products/rate=400
2. http://localhost:8080/webstore/products?rate=400
3. http://localhost:8080/webstore/products?rate/400
4. http://localhost:8080/webstore/products/rate=400
Timeforaction–implementingamaster
detailview
Amasterdetailviewisnothingbutthedisplayofveryimportantinformationonamaster
page.Onceweselectaniteminthemasterview,adetailedpageoftheselecteditemwill
beshowninthedetailviewpage.Let’sbuildamasterdetailviewforourproductlisting
pagesothatwhenweclickonanyproduct,weseethedetailedviewofthatproduct.
Wehavealreadyimplementedtheproductlistingpage
(http://localhost:8080/webshop/products)andproductdetailspage
(http://localhost:8080/webstore/products/product?id=P1234),sotheonlything
neededistoconnectthesetwoviewstomakeamasterdetailview.Performthefollowing
steps:
1. Openproducts.jsp;youcanfindproducts.jspundersrc/main/webapp/WEB-
INF/views/inyourprojectandaddthefollowingspringtaglibreferenceontopof
thefile:
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
2. AddthefollowinglinesaftertheAvailableunitsinstockparagraphtagin
products.jsp:
<p>
<ahref="<spring:urlvalue="/products/product?
id=${product.productId}"/>"class="btnbtn-primary">
<spanclass="glyphicon-info-signglyphicon"/></span>Details
</a>
</p>
3. Now,openproduct.jsp;youcanfindproduct.jspundersrc/main/webapp/WEB-
INF/views/inyourprojectandaddthefollowingspringtaglibreferenceontopof
thefile:
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
And,addthefollowinglinesjustbeforetheOrderNowlinkinproduct.jsp:
<ahref="<spring:urlvalue="/products"/>"class="btnbtn-default">
<spanclass="glyphicon-hand-leftglyphicon"></span>back
</a>
4. RuntheapplicationandentertheURL
http://localhost:8080/webstore/products;youwillbeabletoseeaproductlist
pagethathasaDetailsbuttonwitheveryproduct,asspecifiedinthefollowing
screenshot:
Themasterviewoftheproductlisting
5. Finally,clickonanyproduct’sDetailsbutton,andyouwillbeabletoseethedetail
viewwiththebackbuttonlinktotheproductlistingpage.
Whatjusthappened?
Whatwedidissimple.Instep2,weaddedahyperlinkusingthefollowingtagin
products.jsp:
<ahref="<spring:urlvalue="/products/product?id=${product.productId}"
/>"htmlEscape="true"/>"class="btnbtn-primary">
<spanclass="glyphicon-info-signglyphicon"/></span>Details
</a>
Notethehrefattributeofthe<a>tagasfollows,whichhasa<spring:url>tagasthe
value:
<spring:urlvalue="/products/product?id=${product.productId}"/>
This<spring:url>tagisusedtoconstructavalidSpringURL.Weneededthis
<spring:url>tobeusedinstep2;that’swhyweaddedareferencetothespringtag
libraryinstep1.Observethevalueattributeofthe<spring:url>tag;wecannotethatfor
theidURLparameter,weassignedtheexpression${product.productId}.So,while
renderingthislink,SpringMVCwillassignthecorrespondingproductIDinthat
expression.
Forexample,whilerenderingthelinkofthefirstproduct,SpringMVCwillassignthe
valueP1234fortheproductID.So,thefinalURLvaluewithin<spring:url>willbecome
/products/product?id=P1234,whichisnothingbuttherequestmappingpathofthe
productdetailspage.So,whenyouclickonthislink,youlandonthedetailspageofthat
product.
Similarly,weneedalinktotheproductlistingpagefromtheproductdetailspage;that’s
whyweaddedanotherlinkintheproduct.jsptaginstep4asfollows:
<ahref="<spring:urlvalue="/products"/>"class="btnbtn-default">
<spanclass="glyphicon-hand-leftglyphicon"></span>back
</a>
Notethatthespantagisjustforstylingthebuttonwiththeicon,soyouneedn’tmindit
thatmuch.Theonlyinterestingthingforusisthehrefattributeofthe<a>tag,whichhas
the<spring:url>tagwiththevalueattribute/productsonit.
Haveagohero–addingmultiplefilterstolist
products
ItisgoodthatwelearnedvarioustechniquestobindparameterswithURLs,suchasusing
pathvariables,matrixvariables,andGETparameters.Wesawhowtogetproductsofa
particularcategoryusingpathvariables,howtogetproductswithinaparticularprice
range,andfinally,wesawhowtogetaparticularproductbytheproductID.
Now,imaginethatyouwanttoapplymultiplecriteriatoviewadesiredproduct;for
example,whatifyouwanttoviewaproductthatfallsunderthetabletcategory,iswithin
thepricerangeof$200to$400,andhasbeenmanufacturedbyGoogle?
Toretrieveaproductthatcansatisfyallofthepreviouslymentionedcriteria,wecanform
aURLasfollows:
http://localhost:8080/webstore/products/tablet/price;low=200;high=400?
manufacturer="Google"
Whydon’tyouwriteacorrespondingcontrollermethodtoservetheprecedingrequest
URL?Herearesomehintstoaccomplishtherequirement:
Createarepositorylayermethodtoreturnalltheproductsbasedonmanufacturer.
Forthis,addamethoddeclarationintheproductRepositoryinterfacetogetthe
productsbymanufacturerasfollows:
List<Product>getProductsByManufacturer(Stringmanufacturer);
AddanimplementationforthegetProductsByManufacturer()methodin
InMemoryProductRepository.ItislikethegetProductsByCategory()method;the
onlydifferenceisthatinsteadofthecategory,wefetchtheproductsbymanufacturer
name.
ExtendtheproductServiceinterfacewiththegetProductsByManufacturer()
methodandimplementthesamemethodintheproductServiceImplclass.
CreateonemorerequestmappingmethodcalledfilterProductsinthe
productControllerclasstomapthefollowingURL:
http://localhost:8080/webstore/products/tablet/price;low=200;high=400?
manufacturer="Google"
RememberthatthisURLcontainsthematrixvariableslowandhightorepresentthe
pricerange,theGETparametermanufacturertoidentifythemanufacturer,and
finally,aURItemplatepathvariabletablettorepresentthecategory.
Usethesameviewfileproducts.jsptolistthefilteredproducts.
RememberthatgetProductsByCategoryfromproductServicereturnsproductsbasedon
category,thegetProductsBypriceFiltermethodreturnsproductswithinacertainprice
range,andfinally,ournewlyintroducedmethod,getProductsByManufacturer,returns
productsbelongingtoaparticularmanufacturer.Youhavetocombinethesethreemethod
resultsbeforeupdatingthemodelwiththeproductlistinthefilterProductscontroller
method.Youcanprobablyusejava.util.Settocombinetheresultsofthesethree
servicemethodstoavoidduplication.Goodluck!
Summary
Inthischapter,welearnedhowtodefineacontrollerandtheusageofthe@Controller
annotation.Afterthat,welearnedtheconceptofrelativerequestmapping,wherewesaw
howtodefinerequestmappingatthecontrollerlevelandunderstoodhowSpring
relativelymapsawebrequesttothecontrollerrequestmappingmethod.Wethenlearned
abouttheroleofacontrollerinSpringMVCandabouthowthedispatcherservletuses
handlermappingtofindouttheexacthandlermethods.Wealsosawvariousparameter
bindingtechniques,suchasURItemplatepatterns,matrixvariables,andHTTPGET
requestparameterstobindparameterswithURLs.Finally,wesawhowtoimplementa
masterdetailview.
Inthenextchapter,wearegoingtoexplorevariousSpringtagsthatareavailableinthe
springtaglibrary.Wewillalsolearnmoreaboutformprocessingandhowtobindform
datawiththeHTTPPOSTparameter.Getreadyforthenextchapter!
Chapter4.WorkingwithSpringTag
Libraries
Inpreviouschapters,welearnedhowtoputdataintothemodelfromthecontroller,but
wehaven’tseenhowtodothistheotherwayaround.Thismeansthatwehaven’tlearned
howtoputthedatafromtheviewintothemodel.InSpringMVC,theprocessofputtingan
HTMLformelement’svaluesintomodeldataiscalledformbinding.
SpringMVCprovidessomeJSPtaglibrariestomakeiteasiertobindformelementsto
modeldata.Springtaglibrariesalsosupportvariousothercommonfunctionalities,such
as,externalizingmessagesanderrorhandling.Inthischapter,wearegoingtolearnmore
abouthowtomakeuseofthesepredefinedtaglibrariesofSpring.
Afterfinishingthischapter,wewillhaveagoodideaaboutthefollowingtopics:
Servingandprocessingwebforms
Formbindingandwhitelisting
Springtaglibraries
Servingandprocessingforms
Springsupportsdifferentviewtechnologies,butifweareusingJSP-basedviews,wecan
makeuseoftheSpringtaglibrarytagstomakeupourJSPpages.Thesetagsprovide
manyuseful,commonfunctionalitiessuchasformbinding,evaluatingerrorsoutputting
internationalizedmessages,andsoon.Inordertousethesetags,wemustaddreferences
tothistaglibraryinourJSPpagesasfollows:
<%@taglibprefix="form"uri="http://www.springframework.org/tags/form"%>
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
Inallofourpreviouschapters’examples,wesawthatthedatatransfertookplacefrom
modeltoviewviathecontroller.Thefollowinglineisatypicalexampleofhowweput
dataintothemodelfromacontroller:
model.addAttribute(greeting,"Welcome")
SimilarlythenextlineshowshowweretrievethatdataintheviewusingtheJSTL
expression:
<p>${greeting}</p>
Note
JavaServerPagesStandardTagLibrary(JSTL)isalsoataglibraryprovidedby
Oracle.AnditisacollectionofusefulJSPtagsthatencapsulatesthecorefunctionality
commontomanyJSPpages.WecanaddareferencetotheJSTLtaglibraryinourJSP
pagesas<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>.
However,whatifwewanttoputdataintothemodelfromtheview?Howdoweretrieve
thatdatafromthecontroller?Forexample,considerascenariowhereanadminofour
storewantstoaddnewproductinformationinourstorebyfillingandsubmittingan
HTMLform.HowcanwecollectthevaluesfilledintheHTMLformelementsand
processitinthecontroller?ThisiswheretheSpringtaglibrarytagshelpustobindthe
HTMLtagelement’svaluestoaform-backingbeaninthemodel.Later,thecontrollercan
retrievetheform-backingbeanfromthemodelusingthe@ModelAttributeannotation
(org.springframework.web.bind.annotation.ModelAttribute).
Note
Form-backingbeans(sometimescalledformbeans)areusedtostoreformdata.Wecan
evenuseourdomainobjectsasformbeans;thisworkswellwhenthere’saclosematch
betweenthefieldsontheformandthepropertiesonourdomainobject.Anotherapproach
istocreateseparateclassesforformbeans,whicharesometimescalledDataTransfer
Objects(DTOs).
Timeforaction–servingandprocessing
forms
TheSpringtaglibraryprovidessomespecial<form>and<input>tagsthataremoreor
lesssimilartoHTMLformandinputtags,butithassomespecialattributestobindthe
formelementsdatawiththeform-backingbean.Let’screateaSpringwebforminour
applicationtoaddnewproductstoourproductlistbyperformingthefollowingsteps:
1. WeopenourProductRepositoryinterfaceandaddonemoremethoddeclarationin
itasfollows:
voidaddProduct(Productproduct);
2. WethenaddanimplementationforthismethodintheInMemoryProductRepository
classasfollows:
publicvoidaddProduct(Productproduct){
listOfProducts.add(product);
}
3. WeopenourProductServiceinterfaceandaddonemoremethoddeclarationinitas
follows:
voidaddProduct(Productproduct);
4. And,weaddanimplementationforthismethodintheProductServiceImplclassas
follows:
publicvoidaddProduct(Productproduct){
productRepository.addProduct(product);
}
5. WeopenourProductControllerclassandaddtwomorerequestmappingmethods
asfollows:
@RequestMapping(value="/add",method=RequestMethod.GET)
publicStringgetAddNewProductForm(Modelmodel){
ProductnewProduct=newProduct();
model.addAttribute("newProduct",newProduct);
return"addProduct";
}

@RequestMapping(value="/add",method=RequestMethod.POST)
publicStringprocessAddNewProductForm(@ModelAttribute("newProduct")
ProductnewProduct){
productService.addProduct(newProduct);
return"redirect:/products";
}
6. Finally,weaddonemoreJSPviewfilecalledaddProduct.jspunder
src/main/webapp/WEB-INF/views/andaddthefollowingtagreferencedeclaration
initastheveryfirstline:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglibprefix="form"uri="http://www.springframework.org/tags/form"
%>
7. Now,weaddthefollowingcodesnippetunderthetagdeclarationlineandsave
addProduct.jsp(notethatIhaveskippedthe<form:input>bindingtagsforsomeof
thefieldsoftheproductdomainobject,butIstronglyencouragethatyouaddbinding
tagsfortheskippedfieldswhenyoutryoutthisexercise):
<html>
<head>
<metahttp-equiv="Content-Type"content="text/html;charset=ISO-8859-
1">
<link
rel="stylesheet"href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/boo
tstrap.min.css">
<title>Products</title>
</head>
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1>Products</h1>
<p>Addproducts</p>
</div>
</div>
</section>
<sectionclass="container">
<form:formmodelAttribute="newProduct"class="form-horizontal">
<fieldset>
<legend>Addnewproduct</legend>
<divclass="form-group">
<labelclass="control-labelcol-lg-2col-lg-2"
for="productId">ProductId</label>
<divclass="col-lg-10">
<form:inputid="productId"path="productId"type="text"
class="form:input-large"/>
</div>
</div>
<!--Similarlybind<form:input>tagfor
name,unitPrice,manufacturer,category,unitsInStockandunitsInOrder
fields-->
<divclass="form-group">
<labelclass="control-labelcol-lg-2"
for="description">Description</label>
<divclass="col-lg-10">
form:textareaid="description"path="description"rows=
"2"/>
</div>
</div>
<divclass="form-group">
<labelclass="control-labelcol-lg-2"
for="discontinued">Discontinued</label>
<divclass="col-lg-10">
<form:checkboxid="discontinued"path="discontinued"/>
</div>
</div>

<divclass="form-group">
<labelclass="control-labelcol-lg-2"
for="condition">Condition</label>
<divclass="col-lg-10">
<form:radiobuttonpath="condition"value="New"/>New
<form:radiobuttonpath="condition"value="Old"/>Old
<form:radiobuttonpath="condition"value="Refurbished"
/>Refurbished
</div>
</div>

<divclass="form-group">
<divclass="col-lg-offset-2col-lg-10">
<inputtype="submit"id="btnAdd"class="btnbtn-primary"
value="Add"/>
</div>
</div>
</fieldset>
</form:form>
</section>
</body>
</html>
8. Now,werunourapplicationandentertheURL
http://localhost:8080/webstore/products/add.Wewillbeabletoseeaweb
pagethatdisplaysawebformwherewecanaddtheproductinformationasshownin
thefollowingscreenshot:
Addtheproduct’swebform
9. Now,weenteralltheinformationrelatedtothenewproductthatwewanttoaddand
clickontheAddbutton;wewillseethenewproductaddedintheproductlisting
pageundertheURLhttp://localhost:8080/webstore/products.
Whatjusthappened?
Inthewholesequence,steps5and6areveryimportantstepsthatneedtobeobserved
carefully.Whateverismentionedpriortostep5isfamiliaraswehaveseenitinprevious
recipes;anyhow,Iwillgiveyouabriefnoteonwhatwehavedoneinsteps1to4.
Instep1,wecreatedamethoddeclarationaddProductinourProductRepository
interfacetoaddnewproducts.Instep2,weimplementedtheaddProductmethodinour
InMemoryProductRepositoryclass;theimplementationisjusttoupdatetheexisting
listOfProductsbyaddinganewproducttothelist.Steps3and4arejustaservicelayer
extensionforProductRepository.Instep3,wedeclaredasimilarmethod,addProduct,
inourProductServiceinterfaceandimplementeditinstep4toaddproductstothe
repositoryviatheproductRepositoryreference.
Okay,comingbacktotheimportantstep;wehavedonenothingbutaddedtworequest
mappingmethods,namely,getAddNewProductFormandprocessAddNewProductForm,in
step5asfollows:
@RequestMapping(value="/add",method=RequestMethod.GET)
publicStringgetAddNewProductForm(Modelmodel){
ProductnewProduct=newProduct();
model.addAttribute("newProduct",newProduct);
return"addProduct";
}

@RequestMapping(value="/add",method=RequestMethod.POST)
publicStringprocessAddNewProductForm(@ModelAttribute("newProduct")
ProductproductToBeAdded){
productService.addProduct(productToBeAdded);
return"redirect:/products";
}
Ifyouobservethesemethodscarefully,youwillnoticeapeculiarthing,whichisthatboth
themethodshavethesameURLmappingvalueintheir@RequestMappingannotation
(value="/add").So,ifweentertheURL
http://localhost:8080/webstore/products/addinthebrowser,whichmethodwill
SpringMVCmapthatrequestto?
Theanswerliesinthesecondattributeofthe@RequestMappingannotation(method=
RequestMethod.GETandmethod=RequestMethod.POST).Ifyouwillnoticeagain,even
thoughbothmethodshavethesameURLmapping,theydifferinrequestmethod.
So,whatishappeningbehindthescreenisthatwhenweentertheURL
http://localhost:8080/webstore/products/addinthebrowser,itisconsideredasa
GETrequest.So,SpringMVCmapsthisrequesttothegetAddNewProductFormmethod,
andwithinthismethod,wesimplyattachanewemptyProductdomainobjecttothe
modelundertheattributename,newProduct.
ProductnewProduct=newProduct();
model.addAttribute("newProduct",newProduct);
Sointheviewaddproduct.jsp,wecanaccessthismodelobject,newProduct.Before
jumpingintotheprocessAddNewProductFormmethod,let’sreviewtheaddproduct.jsp
viewfileforsometimesothatweareabletounderstandtheformprocessingflowwithout
confusion.Inaddproduct.jsp,wehavejustaddeda<form:form>tagfromtheSpringtag
libraryusingthefollowinglineofcode:
<form:formmodelAttribute="newProduct"class="form-horizontal">
Sincethisspecial<form:form>tagisacquiredfromtheSpringtaglibrary,weneedtoadd
areferencetothistaglibraryinourJSPfile.That’swhywehaveaddedthefollowingline
atthetopoftheaddProducts.jspfileinstep6:
<%@taglibprefix="form"uri="http://www.springframework.org/tags/form"%>
IntheSpring<form:form>tag,oneoftheimportantattributesismodelAttribute.Inour
case,weassignedthevaluenewProductasthevalueofmodelAttributeinthe
<form:form>tag.Ifyourecallcorrectly,youwillnoticethatthisvalueofmodelAttribute
andtheattributenameweusedtostorethenewProductobjectinthemodelfromour
getAddNewProductFormmethodarethesame.So,thenewProductobjectthatweattached
tothemodelinthecontrollermethod(getAddNewProductForm)isnowboundtotheform.
Thisobjectiscalledtheform-backingbeaninSpringMVC.
Okay,nownoticeeach<form:input>taginsidethe<form:form>tagshowninthe
followingcode.Youwillobservethatthereisacommonattributeineverytag.This
attributenameispath:
<form:inputid="productId"path="productId"type="text"class="form:input-
large"/>
Thepathattributejustindicatesthefieldnamethatisrelativetotheform-backingbean.
So,thevaluethatisenteredinthisinputboxatruntimewillbeboundtothe
correspondingfieldoftheformbean.
Okay,nowisthetimetocomebackandreviewourprocessAddNewProductFormmethod.
Whenwillthismethodbeinvoked?Thismethodwillbeinvokedoncewepressthesubmit
buttonofourform.Yes,sinceeveryformsubmissionisconsideredasaPOSTrequest,
thistimethebrowserwillsendaPOSTrequesttothesameURL,thatis,
http://localhost:8080/webstore/products/add.
So,thistime,theprocessAddNewProductFormmethodwillgetinvokedsinceitisaPOST
request.InsidetheprocessAddNewProductFormmethod,wesimplycalltheservice
methodaddProducttoaddthenewproducttotherepository,asfollows:
productService.addProduct(productToBeAdded);
However,theinterestingquestionhereis,howistheproductToBeAddedobjectpopulated
withthedatathatweenteredintheform?Theanswerlieswithinthe@ModelAttribute
annotation(org.springframework.web.bind.annotation.ModelAttribute).Notethe
methodsignatureoftheprocessAddNewProductFormmethodshowninthefollowingline
ofcode:
publicStringprocessAddNewProductForm(@ModelAttribute("newProduct")
ProductproductToBeAdded)
Here,ifyounoticethevalueattributeofthe@ModelAttributeannotation,youwill
observeapattern.Thevaluesofthe@ModelAttributeannotationandmodelAttribute
fromthe<form:form>tagarethesame.So,SpringMVCknowsthatitshouldassignthe
form-boundnewProductobjecttotheproductToBeAddedparameterofthe
processAddNewProductFormmethod.
The@ModelAttributeannotationisnotonlyusedtoretrieveanobjectfromamodel,but
ifwewantto,wecanevenuseittoaddobjectstothemodel.Forinstance,werewriteour
getAddNewProductFormmethodtosomethinglikethefollowingcodewiththeuseofthe
@ModelAttributeannotation:
@RequestMapping(value="/add",method=RequestMethod.GET)
publicStringgetAddNewProductForm(@ModelAttribute("newProduct")Product
newProduct){
return"addProduct";
}
Youcannoticethatwehaven’tcreatedanynewemptyProductdomainobjectand
attachedittothemodel.AllwehavedonewasaddedaparameterofthetypeProductand
annotateditwiththe@ModelAttributeannotationsothatSpringMVCwouldknowthatit
shouldcreateanobjectofProductandattachittothemodelunderthenamenewProduct.
OnemorethingthatneedstobeobservedintheprocessAddNewProductFormmethodis
thelogicalviewname,redirect:/products,thatitreturns.So,whatarewetryingtotell
SpringMVCbyreturningastringredirect:/products?Togettheanswer,observethe
logicalviewnamestringcarefully.Ifwesplitthisstringwiththe:(colon)symbol,we
willgettwoparts;thefirstpartistheprefixredirectandthesecondpartissomething
thatlookslikearequestpath,/products.So,insteadofreturningaviewname,wesimply
instructSpringtoissuearedirectrequesttotherequestpath,/products,whichisthe
requestpathforthelistmethodofourProductControllerclass.So,aftersubmittingthe
form,welisttheproductsusingthelistmethodofProductController.
Note
Asamatteroffact,whenwereturnanyrequestpathwiththeredirect:prefixfroma
requestmappingmethod,Springusesaspecialviewobject,RedirectView
(org.springframework.web.servlet.view.RedirectView),toissuearedirectcommand
behindthescreen.WewillseemoreaboutRedirectViewintheupcomingchapter.
Insteadoflandinginawebpageafterthesuccessfulsubmissionofawebform,weare
spawninganewrequesttotherequestpath/productswiththehelpofRedirectView.
ThispatterniscalledRedirectAfterPost,whichisacommonpatterntousewithweb-
basedforms.Weareusingthispatterntoavoiddoublesubmissionofthesameform;
sometimes,ifwepressthebrowser’srefreshbuttonorbackbuttonaftersubmittingthe
form,therearechancesthatthesameformwillberesubmitted.
Customizingdatabinding
Inthelastsection,wesawhowtobinddatasubmittedbyanHTMLformorbyquery
stringparameterstoaform-backingbean.Inordertodothebinding,SpringMVC
internallyusesaspecialbindingobjectcalledWebDataBinder
(org.springframework.web.bind.WebDataBinder).
TheWebDataBinderobjectextractsthedataoutoftheHttpServletRequestobject,
convertsittoaproperdataformat,loadsitintoaform-backingbean,andvalidatesit.To
customizethebehaviorofthedatabinding,wecaninitializeandconfigurethe
WebDataBinderobjectinourcontroller.The@InitBinderannotation
(org.springframework.web.bind.annotation.InitBinder)helpsusdothis.The
@InitBinderannotationdesignatesamethodtoinitializeWebDataBinder.
Let’sseeapracticalwayofcustomizingWebDataBinder.Sinceweareusingtheactual
domainobjectitselfastheform-backingbean,duringformsubmission,thereisachance
ofsecurityvulnerability.SinceSpringautomaticallybindsHTTPparameterstoformbean
properties,anattackercouldbindsuitablynamedHTTPparameterswithformproperties
thatweren’tintendedforbinding.Toaddressthisproblem,wecanexplicitlytellSpring
whichfieldsareallowedforformbinding.Technicallyspeaking,theprocessofexplicitly
specifyingtheallowedfieldsforformbindingiscalledwhitelistingformfieldsinSpring
MVC;wecandowhitelistingusingWebDataBinder.
Timeforaction–whitelistingformfields
Inthepreviousexercise,whileaddinganewproduct,weboundeveryfieldoftheProduct
domainintheform.However,itismeaninglesstospecifytheunitsInOrderand
discontinuedvaluesduringtheadditionofanewproductbecausenobodycanmakean
orderbeforeaddingtheproducttothestore,andsimilarly,thediscontinuedproducts
neednotbeaddedinourproductlist.So,weshouldnotallowthesefieldstobeboundto
theformbeanwhileaddinganewproducttoourstore.However,alltheotherfieldsofthe
Productdomainobjectneedtobebound.Let’sseehowtodothiswiththefollowing
steps:
1. WeopenourProductControllerclassandaddamethodasfollows:
@InitBinder
publicvoidinitialiseBinder(WebDataBinderbinder){
binder.setDisallowedFields("unitsInOrder","discontinued");
}
2. WethenaddanextraparameterofthetypeBindingResult
(org.springframework.validation.BindingResult)tothe
processAddNewProductFormmethodasfollows:
publicStringprocessAddNewProductForm(@ModelAttribute("newProduct")
ProductproductToBeAdded,BindingResultresult)
3. InthesameprocessAddNewProductFormmethod,weaddthefollowingconditionjust
beforethelinewherewesavedtheproductToBeAddedobject:
String[]suppressedFields=result.getSuppressedFields();
if(suppressedFields.length>0){
thrownewRuntimeException("Attemptingtobinddisallowedfields:"
+StringUtils.arrayToCommaDelimitedString(suppressedFields));
}
4. Now,werunourapplicationandentertheURL
http://localhost:8080/webstore/products/add;wewillbeabletoseeaweb
pagethatdisplaysawebformwherewecanaddnewproductinformation.Let’sfill
everyfield,particularlyUnitsinorderandDiscontinued.
5. Now,clickontheAddbutton.YouwillseeanHTTPStatus500errorontheweb
page,asshowninthefollowingscreenshot:
Addproductpageshowingerrorfordisallowedfields
6. Now,weopenaddProduct.jspfrom/webstore/src/main/webapp/WEB-INF/views/
inourprojectandremovetheinputtagsthatarerelatedtotheUnitsinorderand
Discontinuedfields.Basically,weneedtoremovethefollowingblockofcode:
<divclass="form-group">
<labelclass="control-labelcol-lg-2"for="unitsInOrder">UnitsIn
Order</label>
<divclass="col-lg-10">
<form:inputid="unitsInOrder"path="unitsInOrder"type="text"
class="form:input-large"/>
</div>
</div>
<divclass="form-group">
<labelclass="control-labelcol-lg-2"
for="discontinued">Discontinued</label>
<divclass="col-lg-10">
<form:checkboxid="discontinued"path="discontinued"/>
</div>
</div>
7. Now,werunourapplicationagainandentertheURL
http://localhost:8080/webstore/products/add.Wewillbeabletoseeaweb
pagethatdisplaysawebformwherewecanaddanewproduct,butthistime,
withouttheUnitsinorderandDiscontinuedfields.
8. Now,weenteralloftheinformationrelatedtothenewproductandclickontheAdd
button;wewillseethenewproductaddedintheproductlistingpageundertheURL
http://localhost:8080/webstore/products.
Whatjusthappened?
OurintentionwastoputsomerestrictionsonbindingtheHTTPparameterswiththeform-
backingbean.Aswealreadydiscussed,theautomaticbindingfeatureofSpringcouldlead
toapotentialsecurityvulnerability,incaseweusedthedomainobjectitselfastheform
bean.So,wehavetoexplicitlyspecifytoSpringMVCwhattheonlyallowedfieldsare.
That’swhatwedidinstep1.
The@InitBinderannotationdesignatesacontrollermethodasahookmethodtodosome
customconfigurationregardingdatabindingonWebDataBinder.And,WebDataBinderis
theonethatdoesthedatabindingatruntime,soweneedtospecifytoWebDataBinder
onlythefieldsallowedforbinding.IfyouobserveourinitialiseBindermethodfrom
ProductController,ithasaparametercalledbinder,whichisofthetype
WebDataBinder.WesimplycallthesetAllowedFieldsmethodonthebinderobjectand
passthefields’namesthatareallowedforbinding.SpringMVCcallsthismethodto
initializeWebDataBinderbeforebindingsinceithasthe@InitBinderannotation.
Note
TheWebDataBinderclassalsohasamethodcalledsetDisallowedFieldstostrictly
specifythedisallowedfieldsforbinding.Ifyouusethismethod,SpringMVCallowsany
HTTPrequestparameterstobebound,exceptthatthesefieldnamesarespecifiedinthe
setDisallowedFieldsmethod.
Okay,weconfiguredwhichfieldsareallowedforbinding,butweneedtoverifywhether
anyotherfieldsotherthantheonesallowedareboundwiththeform-backingbean.That’s
whatwedidinsteps2and3.
WechangedprocessAddNewProductFormbyaddingoneextraparametercalledresult,
whichisofthetypeBindingResult.SpringMVCwillfillthisobjectwiththeresultofthe
binding.Ifanyattemptismadetobindanythingotherthantheallowedfields,the
getSuppressedFieldscountoftheBindingResultobjectwillbegreaterthanzero.That’s
why,wecheckedsuppressedfieldcountandthrewRuntimeExceptionasfollows:
if(suppressedFields.length>0){
thrownewRuntimeException("Attemptingtobinddisallowedfields:"+
StringUtils.arrayToCommaDelimitedString(suppressedFields));
}
Wewantedtoensurethatourbindingconfigurationisworking;that’swhy,weranour
applicationwithoutchangingtheviewfileaddProduct.jspinstep4.Asexpected,wegot
theHTTPStatus500errorsayingAttemptingtobinddisallowedfieldswhenwe
submittedtheaddproductformwiththeunitsInOrderanddiscontinuedfieldsfilled.
Werealizedthatourbinderconfigurationisworking,sowechangedourviewfiletonot
bindthedisallowedfields.That’swhatwedidinstep6;wejustremovedtheinputfield
elementsthatarerelatedtothedisallowedfieldsfromtheaddProduct.jspfile.
Afterthis,ourpageforaddingnewproductsworksjustfine,asexpected.Incaseanyof
theoutsideattackerstrytotamperthePOSTrequestandattachaHTTPparameterwiththe
samefieldnameoftheform-backingbean,theywillgetRuntimeException.
Whitelistingisjustanexampleofhowwecancustomizethebindingwiththehelpof
WebDataBinder.However,usingWebDataBinder,wecandoothertypesofbinding
customizationsaswell.Forexample,WebDataBinderinternallyusesmany
PropertyEditor(java.beans.PropertyEditor)implementationstoconvertHTTP
requestparameterstothetargetfieldoftheform-backingbean.Wecanevenregisterthe
customPropertyEditorobjectswithWebDataBindertoconvertmorecomplexdatatypes.
Forinstance,takealookatthefollowingcodesnippetthatshowshowtoregisterthe
customPropertyEditorclasstoconvertaDatetype:
@InitBinder
publicvoidinitialiseBinder(WebDataBinderbinder){
DateFormatdateFormat=newSimpleDateFormat("MMMd,YYYY");
CustomDateEditororderDateEditor=newCustomDateEditor(dateFormat,
true);
binder.registerCustomEditor(Date.class,orderDateEditor);
}
TherearemanyadvancedconfigurationswecandowithWebDataBinderintermsofdata
binding,butforabeginnerlevel,wedon’tneedtogosodeep.
Externalizingtextmessages
Sofar,inallourviewfiles,wehardcodedtextvaluesforallofthelabels.Forinstance,
takeouraddProduct.jspfilefortheproductIDinputtag;wehavealabeltagwitha
hardcodedtextvalueasProductId,asfollows:
<labelclass="control-labelcol-lg-2col-lg-2"for="productId">Product
Id</label>
Externalizingthesetextsfromaviewfileintoapropertiesfilewillhelpushavesingle,
centralizedcontrolofallthelabelmessages,andmoreover,itwillhelpusmakeourweb
pagesreadyforinternationalization.Wewillseemoreaboutinternationalizationin
Chapter6,InterceptYourStorewithInterceptor,butinordertodointernationalization,we
needtoexternalizethelabelmessagesfirst.Sonow,wearegoingtoseeonlyhowto
externalizethelocale-sensitivetextmessagesfromourwebpage.
Timeforaction–externalizingmessages
Let’sseehowtoexternalizethelabeltextsinouraddProduct.jspfile:
1. WeopenouraddProduct.jspfileandaddthefollowingtaglibreferenceatthetop:
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
2. ChangetheproductID<label>tag’svalueas<spring:message
code="addProdcut.form.productId.label"/>,asshownasfollows:
<labelclass="control-labelcol-lg-2col-lg-2"for="productId">
<spring:messagecode="addProduct.form.productId.label"/></label>
3. Wecreateafilecalledmessages.propertiesunder/src/main/resourcesinour
projectandaddthefollowinglineinit:
addProduct.form.productId.label=NewProductID
4. Now,weopenourwebapplicationcontextconfigurationfileDispatcherServlet-
context.xmlfromsrc/main/webapp/WEB-INF/spring/webcontext/andaddthe
followingbeandefinitioninit:
<beanid="messageSource"
class="org.springframework.context.support.ResourceBundleMessageSource"
>
<propertyname="basename"value="messages"/>
</bean>
5. Now,werunourapplicationagainandentertheURL
http://localhost:8080/webstore/products/add.Wewillbeabletoseetheadd
productpagewiththeproductIDlabelNewProductID.
Whatjusthappened?
SpringMVChasaspecialatagcalled<spring:message>toexternalizetextsfromJSP
files.Inordertousethistag,weneedtoaddareferencetotheSpringtaglibrary,whichis
whatwedidinstep1.WejustaddedareferencetotheSpringtaglibraryinour
addProduct.jspfileasfollows:
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
Instep2,weusedthistagtoexternalizethelabeltextoftheproductIdinputtag,as
follows:
<labelclass="control-labelcol-lg-2col-lg-2"for="productId">
<spring:messagecode="addProduct.form.productId.label"/></label>
Here,animportantthingthatneedstobenotedisthecodeattributeofthe
<spring:message>tagthatwehaveassignedthevalue
addProduct.form.productId.labelasthecodeforthis<spring:message>tag.This
codeattributeisakindofkey,andatruntime,Springwilltrytoreadthecorresponding
valueforthegivenkey(code)fromamessagesourcepropertyfile.
WesaidthatSpringwillreadthemessagevaluefromamessagesourcepropertyfile,so
weneedtocreatethatpropertyfile,whichiswhatwedidinstep3.Wejustcreateda
propertyfilewiththenamemessages.propertiesundertheresourcedirectory.Insidethis
file,weassignedthelabeltextvaluetothemessagetagcodeasfollows:
addProduct.form.productId.label=NewProductID
Notethatfordemonstrationpurposes,Ijustexternalizedasinglelabel,butatypicalweb
applicationwillhaveexternalizedmessagesalmostforallofthelabels.Inthatcase,the
messages.propertiesfilewillhavemanycode-valuepairentries.
Okay,wehavecreatedthemessagesourcepropertyfileandaddedthe<spring:message>
taginourJSPfile.However,toconnectthesetwo,weneedtocreateonemoreSpring
beaninourwebapplicationcontextforthe
org.springframework.context.support.ResourceBundleMessageSourceclasswiththe
namemessageSource.Wedidthisinstep4asfollows:
<beanid="messageSource"
class="org.springframework.context.support.ResourceBundleMessageSource">
<propertyname="basename"value="messages"/>
</bean>
Oneimportantpropertythatneedstobenotedhereisthebasenameproperty.Weassigned
thevaluemessagesforthatproperty;ifyouremember,thisisthenameofthepropertyfile
thatwecreatedinstep3.
ThatisallthatwehavedonetoenabletheexternalizationofmessagesinaJSPfile.Now,
ifweruntheapplicationandopenuptheaddproductpage,wecanseethattheproductID
labelhasthesametextasthatassignedtothecodeaddProduct.form.productId.label
inthemessages.propertiesfile.
UsingSpringSecuritytags
Atthestartofthischapter,wesawhowtoserveandprocesswebforms.Inthatexercise,
wecreatedawebpagetoaddproducts.Anyonewithaccesstotheaddproductspagecan
addnewproductstoourwebstore.However,inatypicalwebstore,onlytheadministrator
canaddproducts.So,howdowerestrictotherusersfromaccessingtheaddproducts
page?TherecomesSpringSecuritytohelpus.
SpringSecurityisavasttopic,sowearenotgoingtoseeallofthecapabilitiesofSpring
Security;instead,weareonlygoingtoseehowtoaddbasicauthenticationtoourweb
pages.
Timeforaction–addingaloginpage
WearegoingtouseSpringSecurityfeaturestorestrictaccesstotheaddproductspage.
Onlyanauthorizeduserwithavalidusernameandpasswordwillbeabletoaccesstheadd
productspage.Let’sseehowwecandothisinSpringMVCwiththefollowingsteps:
1. Weopenpom.xml,whichcanbefoundundertheprojectrootfolderitself.
2. Wewillbeabletoseesometabsatthebottom,underthepom.xmlfile;weselectthe
DependenciestabandclickontheAddbuttonoftheDependenciessection.
3. ASelectDependencywindowwillappear;here,weenterGroupIdas
org.springframework.security,ArtifactIdasspring-security-config,Version
as3.1.4.RELEASE,andselectScopeascompileandclickontheOKbutton.
4. Similarly,weaddonemoredependencyGroupIdas
org.springframework.security,ArtifactIdasspring-security-web,Versionas
3.1.4.RELEASE,andselectScopeascompileandclickontheOKbutton.Andmost
importantly,wesavepom.xml.
5. Now,wegototheadjacenttab,whichistheDependencyHierarchytabinpom.xml.
WecanseetheResolvedDependenciessectionontheright,whichlistsallthe
resolveddependencyentries.
6. Wejustright-clickontheentrywiththenamespring-
asm:3.0.7.RELEASE[compile]fromtheResolvedDependencieslistandchoosethe
ExcludeMavenArtifact…optionandclickonOK.Then,wesavepom.xml.
7. Now,wecreateonemorecontrollerclasscalledLoginControllerunderthe
com.packt.webstore.controllerpackageinsrc/main/javaandaddthefollowing
codeintoit:
packagecom.packt.webstore.controller;
importorg.springframework.stereotype.Controller;
importorg.springframework.ui.Model;
importorg.springframework.web.bind.annotation.RequestMapping;
importorg.springframework.web.bind.annotation.RequestMethod;
@Controller
publicclassLoginController{
@RequestMapping(value="/login",method=RequestMethod.GET)
publicStringlogin(){
return"login";
}
@RequestMapping(value="/loginfailed",method=RequestMethod.GET)
publicStringloginerror(Modelmodel){
model.addAttribute("error","true");
return"login";
}
@RequestMapping(value="/logout",method=RequestMethod.GET)
publicStringlogout(Modelmodel){
return"login";
}
}
8. And,weaddonemoreJSPviewfilecalledlogin.jspundersrc/main/webapp/WEB-
INF/views/andaddthefollowingcodesnippetintoitandsaveit:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglibprefix="form"uri="http://www.springframework.org/tags/form"
%>
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"
%>
<html>
<head>
<metahttp-equiv="Content-Type"content="text/html;charset=ISO-8859-
1">
<link
rel="stylesheet"href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/boo
tstrap.min.css">
<title>Products</title>
</head>
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1>Products</h1>
<p>Addproducts</p>
</div>
</div>
</section>
<divclass="container">
<divclass="row">
<divclass="col-md-4col-md-offset-4">
<divclass="panelpanel-default">
<divclass="panel-heading">
<h3class="panel-title">Pleasesignin</h3>
</div>
<divclass="panel-body">
<c:iftest="${notemptyerror}">
<divclass="alertalert-danger">
<spring:message
code="AbstractUserDetailsAuthenticationProvider.
badCredentials"/><br/>
</div>
</c:if>
<formaction="<c:urlvalue="/j_spring_security_check">
</c:url>"method="post">
<fieldset>
<divclass="form-group">
<inputclass="form-control"placeholder="UserName"
name='j_username'type="text">
</div>
<divclass="form-group">
<inputclass="form-control"placeholder="Password"
name='j_password'type="password"value="">
</div>
<inputclass="btnbtn-lgbtn-successbtn-block"
type="submit"value="Login">
</fieldset>
</form>
</div>
</div>
</div>
</div>
</div>
</body>
9. Now,weopenouraddProduct.jspfileandaddthefollowingcodetagwithinthe
jumbotrondivtag:
<ahref="<c:urlvalue="/j_spring_security_logout"/>"class="btnbtn-
dangerbtn-minipull-right">logout</a>
10. Then,weopenourmessagesourcefilemessages.propertiesfrom
/src/main/resourcesandaddthefollowinglineinit:
AbstractUserDetailsAuthenticationProvider.badCredentials=Theusername
orpasswordyouenteredisincorrect.
11. Now,wecreateonemorebeanconfigurationfilecalledsecurity-context.xml
undersrc/main/webapp/WEB-INF/spring/webcontextandaddthefollowing
contentintoitandsaveit:
<?xmlversion="1.0"encoding="UTF-8"?>
<beansxmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:security="http://www.springframework.org/schema/security"
xsi:schemaLocation="http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
http://www.springframework.org/schema/security
http://www.springframework.org/schema/security/spring-security-3.1.xsd
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.2.xsd">

<security:httpauto-config="true">
<security:intercept-urlpattern="/products/add"access="ROLE_ADMIN"
/>

<security:form-loginlogin-page="/login"
default-target-url="/products/add"
authentication-failure-url="/loginfailed"/>
<security:logoutlogout-success-url="/logout"/>
</security:http>

<security:authentication-manager>
<security:authentication-provider>
<security:user-service>
<security:username="Admin"password="Admin123"
authorities="ROLE_ADMIN"/>
</security:user-service>
</security:authentication-provider>
</security:authentication-manager>
</beans>
12. Then,weaddthefollowingtagsinweb.xmlunderthe<web-app>tag:
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>
/WEB-INF/spring/webcontext/security-context.xml
</param-value>
</context-param>

<listener>
<listener-class>
org.springframework.web.context.ContextLoaderListener
</listener-class>
</listener>
13. Now,wealsoaddthefollowingtagsinweb.xmlunderthe<web-app>tagandsaveit:
<filter>
<filter-name>springSecurityFilterChain</filter-name>
<filter-class>
org.springframework.web.filter.DelegatingFilterProxy
</filter-class>
</filter>

<filter-mapping>
<filter-name>springSecurityFilterChain</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
14. WerunourapplicationandentertheURL
http://localhost:8080/webstore/products/add.Wewillbeabletoseealogin
page,asshowninthefollowingscreenshot:
Theloginpageshowinganerrormessageforinvalidcredentials
15. Now,weenterUserNameasAdminandPasswordasAdmin123andclickonthe
Loginbutton.Finally,wewillbeabletoseetheregularaddproductspagewitha
Logoutbutton.
Whatjusthappened?
Asusual,inordertouseSpringSecurityinourproject,weneedsomeSpringSecurity
relatedjars;fromsteps1to4,wejustaddedthosejarsasMavendependencies.However,
wedidsomethingunusualinsteps5and6.Weexcludedthespring-asmdependency
(spring-asm:3.0.7.RELEASE[compile])fromtheresolveddependencieslist.
FromtheSpring3.2versiononwards,thespring-asmmodulehadalreadybeenincluded
inthespring-coremodule,sothereisnoneedtohavespring-asmasaseparate
transitivedependency.Ifyouhaveskippedsteps5and6,youwillget
java.lang.IncompatibleClassChangeErrorwhenstartinguptheproject.
Instep7,wecreatedonemorecontroller(LoginController)tohandleallourlogin-
relatedwebrequeststhatcontainsimplythreerequestmappingmethodscorrespondingly
tohandlelogin,loginfailure,andlogoutrequests.Allthreemethodsreturnthesameview
name,outofwhichtheloginerrormethodsetsamodelvariableerrortotrueinthe
model.
Sinceinstep7,alltherequestmappingmethodsreturntheviewnamelogin,weneedto
createaviewfilelogin.jsp,whichiswhatwedidinstep8.
Thelogin.jspfilecontainsmanytagswithaBootstrap-styleclassappliedtoenhancethe
lookandfeeloftheloginform;wedon’tneedtoconcentrateonthesetags.However,
therearesomeimportanttagsouttherethatcanbeusedtounderstandtheflow;thefirst
oneisthe<c:if>tag,asshowninthefollowingcode:
<c:iftest="${notemptyerror}">
<divclass="alertalert-danger">
<spring:message
code="AbstractUserDetailsAuthenticationProvider.badCredentials"/>
</div>
</c:if>
The<c:if>tagisaspecialJSTLtagusedtocheckacondition;itismorelikeanif
conditionthatweuseinourprogramminglanguage.Usingthis<c:if>tag,wesimply
checkwhetherthemodelvariableerrorcontainsanyvalue.Ifthemodelvariableerroris
notempty,wesimplyshowanerrormessagewithinthedivtagusingthe
<spring:message>tag.
RememberthatfromtheExternalizingtextmessagesexercise,wealreadylearned
howtoexternalizemessages.Inthisrecipe,wesimplyusedthepredefinederrorkey,
AbstractUserDetailsAuthenticationProvider.badCredentials,ofSpringSecurityas
themessagekey.Sincewedidthis,wejustoverrodethedefaulterrormessageinstep10.
Okay,comingbacktostep8,whataretheotherimportanttagsinthelogin.jspfile?The
nextimportanttagistheformtag,whichrepresentstheloginform.Notetheaction
attributeoftheformtagshowninthefollowingcode:
<formaction="<c:urlvalue="/j_spring_security_check"></c:url>"
method="post">
Wesimplypostourloginformvalues,suchasusernameandpassword,totheSpring
SecurityauthenticationhandlerURL,whichis/j_spring_security_check.Here,the
special<c:url>JSTLtagisusedtoformattheURL.
WhilepostingtheusernameandpasswordtotheSpringSecurityauthenticationhandler,
Springexpectsthesevaluestobeboundunderthevariablenamesj_usernameand
j_passwordcorrespondingly.That’swhy,ifyounoticetheinputtagfortheusernameand
password,itcarriesthenameattributesasj_usernameandj_password,asfollows:
<inputclass="form-control"placeholder="UserName"name='j_username'
type="text">
<inputclass="form-control"placeholder="Password"name='j_password'
type="password"value="">
Similarly,Springhandlesthelogoutoperationunderthej_spring_security_logout
URL;that’swhy,instep9,weformedthelogoutlinkontheaddproductspageasfollows:
<ahref="<c:urlvalue="/j_spring_security_logout"/>"class="btnbtn-danger
btn-minipull-right">logout</a>
WearealmostdonewiththecodingtoincorporateSpringSecurityintoourproject,but
stillweneedtodosomemoreconfigurationtogetitupandrunningwiththebasic
authenticationfortheaddproductspage.Forthefirstconfiguration,weneedtodefineour
authenticationmanagerandspecifytheauthenticatedusersandrolestoSpringSecurity.
Wedidthiswiththehelpofasecuritycontextfile.
Asecuritycontextfileismoresimilartoawebapplicationcontextconfigurationfile.
Basedontheconfigurationandbeandefinitionfoundinthisfile,Springcreatesand
managesthenecessarybeansrelatedtoSpringSecurity.Wecreatedsuchasecurity
contextfileinstep11.Thefirstconfigurationtagthatisfoundinthissecuritycontextfile
(security-context.xml)is<security:http>,asfollows:
<security:httpauto-config="true">
<security:intercept-urlpattern="/products/add"access="ROLE_ADMIN"/>

<security:form-loginlogin-page="/login"
default-target-url="/products/add"
authentication-failure-url="/loginfailed"/>
<security:logoutlogout-success-url="/logout"/>
</security:http>
The<security:http>tagcontainsalotofinformation,andwewillseethemonebyone.
Thefirstconfigurationwithinthe<security:http>tagisasfollows:
<security:intercept-urlpattern="/products/add"access="ROLE_ADMIN"/>
ThisinstructsSpringtointercepteverywebrequestthatisreceivedbytherequestpath
/products/addandonlyallowsaccesstowhicheveruserhastheroleofROLE_ADMIN.If
yourecall,/products/addisnothingbuttherequestpathforouraddproductspage.
Thenextconfigurationwithinthe<security:http>tagisasfollows:
<security:form-loginlogin-page="/login"
default-target-url="/products/add"
authentication-failure-url="/loginfailed"/>
Here,thelogin-pageattributedenotestheURLthatitshouldforwardtherequestto,to
gettheloginform;rememberthatthisrequestpathshouldbethesameastherequest
mappingofthelogin()methodofLoginController.Also,default-target-urldenotes
thedefaultlandingpageafterasuccessfullogin,andthefinalattributeauthentication-
failure-urlindicatestheURLthattherequestneedstobeforwardedtointhecaseofa
loginfailure.
Thefinalconfiguration,<security:logoutlogout-success-url="/logout"/>,denotes
wheretherequestneedstobeforwardedafteralogout.Rememberthatthisalsocarriesthe
samerequestmappingvalue,whichisthevalueofthelogoutmethod,fromthe
LoginControllerclass.
Thenextconfigurationtaginthesecuritycontextfileisthe<security:authentication-
manager>tag;refertothefollowingcode:
<security:authentication-manager>
<security:authentication-provider>
<security:user-service>
<security:username="Admin"password="Admin123"
authorities="ROLE_ADMIN"/>
</security:user-service>
</security:authentication-provider>
</security:authentication-manager>
Theimportantinformationconfiguredundertheauthenticationmanageriswhotheusers
are,whattheircorrespondingpasswordis,andwhichrolestheyhave,asfollows:
<security:username="Admin"password="Admin123"authorities="ROLE_ADMIN"/>
TheprecedingpieceofconfigurationsaysthatitisauserwiththenameAdminandhasa
passwordAdmin123andaroleROLE_ADMIN.Wecanaddasmanyrolesaswewantby
separatingthemwithacomma.
Okay,wedefinedthesecurity-relatedconfigurationinthesecuritycontextfile,butSpring
shouldknowaboutthisfileandhavetoreadthisfilebeforebootingtheapplication.Then
onlywillitbeabletocreateandmanagethesecurity-relatedbeans.Howdoweinstruct
Springtopickupthisfile?Theansweristhesame:thecontextConfigLocationlocation
propertythatwehaveusedtolocatethewebapplicationcontextconfigurationfile.
However,thistime,weloadedthesecuritycontextfilethroughthe
ContextLoaderListenerclassandnotthroughthedispatcherservlet.That’swhy,we
initiatedContextLoaderListenerinweb.xmlandgavecontextConfigLocationviathe
<context-param>taginstep12,asfollows:
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/spring/webcontext/security-context.xml</param-
value>
</context-param>

<listener>
<listener-class>
org.springframework.web.context.ContextLoaderListener
</listener-class>
</listener>
Basedontheprecedingconfiguration,theContextLoaderListenerclasswillloadour
securitycontextfile(/WEB-INF/spring/webcontext/security-context.xml)intothe
SpringruntimesothatSpringcancreatethenecessarybeanswhilebootingthe
application.
Asafinalstep,weneedtoconfiguretheSpringSecurityfilterinourweb.xmlfilesothat
everywebrequestcanbeexaminedforuserauthentication.Thisiswhatweconfiguredin
step13,asfollows:
<filter>
<filter-name>springSecurityFilterChain</filter-name>
<filter-class>
org.springframework.web.filter.DelegatingFilterProxy
</filter-class>
</filter>

<filter-mapping>
<filter-name>springSecurityFilterChain</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
Afterfinishingallthesteps,ifweaccesstheURL
http://localhost:8080/WebStore/products/add,SpringMVCwillpromptusto
providetheusernameandpassword.Sincewehaveconfiguredanadminuserinstep11
withUserNameasAdminandPasswordasAdmin123,wehavetoprovidethese
credentialstoproceedtotheaddproductspage.
Summary
Atthestartofthischapter,wesawhowtoserveandprocessforms;welearnedhowto
bindformdatawithaform-backingbeanandreadthatbeaninthecontroller.Afterthat,
wewentalittledeeperintoformbeanbindingandconfiguredthebinderinourcontroller
towhitelistsomeofthePOSTparametersfrombeingboundtotheformbean.Wesaw
howtouseonemorespecialtag,<spring:message>,ofSpringtoexternalizemessagesin
aJSPfile.Finallywealsosawhowtoincorporatespringsecuritytodobasic
authenticationtoaccessproductaddpage.
Inthenextchapter,wewilllearnmoreaboutviewandviewresolvers.
Chapter5.WorkingwithViewResolver
Inthepreviouschapter,welearnedhowwecanusesomeoftheSpringtagsthatcanonly
beusedinJSPandJSTLviews.However,Springhasexcellentsupportforotherview
technologiesaswell,suchastheXMLview,JSONview,andsoon.SpringMVCmaintains
ahighlevelofdecouplingbetweentheviewandcontroller.Thecontrollerknowsnothing
aboutviewexcepttheviewname.Itistheresponsibilityoftheviewresolvertomapthe
correctviewforthegivenviewname.
Inthischapter,wewilltakeadeeperlookintoviewsandviewresolvers.Afterfinishing
thischapter,youwillhaveaclearideaaboutthefollowingtopics:
Viewsandresolvingviews
Staticviews
Themultipartviewresolver
Contentnegotiation
Thehandlerexceptionresolver
Resolvingviews
Aswealreadymentioned,SpringMVCdoesnotmakeanyassumptionaboutanyspecific
viewtechnology.AccordingtoSpringMVC,aviewisidentifiableasanimplementation
oftheorg.springframework.web.servlet.Viewinterface,shownasfollows:
publicinterfaceView{
StringgetContentType();
voidrender(Map<String,?>model,HttpServletRequestrequest,
HttpServletResponseresponse)throwsException;
}
TherendermethodfromtheSpringMVCViewinterfacedefinesthemainresponsibility
ofaviewobject.Theresponsibilityisthatitshouldrenderofpropercontentasaresponse
(javax.servlet.http.HttpServletResponse)basedonModelandrequest
(javax.servlet.http.HttpServletRequest).
BecauseofthesimplicityofSpringMVC’sViewinterface,wecanwriteourownview
implementationifwewant.However,SpringMVCprovidesmanyconvenientview
implementationsthatarereadyforusebysimplyconfiguringitinourwebapplication’s
contextconfigurationfile.
OnesuchviewisInternalResourceView
(org.springframework.web.servlet.view.InternalResourceView),whichrendersthe
responseasaJSPpage.Similarly,thereareotherviewimplementationssuchas
RedirectView,TilesView,FreeMarkerView,andVelocityView,whichareavailablefor
specificviewtechnologies.SpringMVCdoesnotencouragecouplingtheviewobject
withthecontrollerasitwillleadthecontrollermethodtotightlycouplewithonespecific
viewtechnology.However,ifyouwanttodoso,youcandosomethingsimilartowhatis
showninthefollowingcodesnippet:
@RequestMapping("/home")
publicModelAndViewgreeting(Map<String,Object>model){

model.put("greeting","WelcometoWebStore!");
model.put("tagline","Theoneandonlyamazingwebstore");

Viewview=newInternalResourceView("/WEB-INF/views/welcome.jsp");

returnnewModelAndView(view,model);
}
Intheprecedingcodehandlermethod,wehaven’treturnedanylogicalviewname;rather,
wedirectlyinstantiatedInternalResourceViewoutofwelcome.jspandcomposeditinto
theModelAndView(org.springframework.web.servlet.ModelAndView)object.The
precedingexampleisnotencouragedsinceithastightlycoupledthegreetinghandler
methodwithInternalResourceView.Instead,whatwecandoisreturnalogicalview
nameandconfigureanappropriateviewresolverofourchoiceinourwebapplication’s
contexttocreateaviewobject.
Springcomeswithquiteafewviewresolverstoresolvevarioustypesofviews.We
alreadylearnedhowwecanconfigureInternalResourceViewResolverasourview
resolvertoresolveJSPviewsinChapter2,SpringMVCArchitecture–ArchitectingYour
WebStore,andwealsolearnedhowInternalResourceViewResolverresolvesa
particularlogicalviewnameintoaview(seetheViewresolverssection,inChapter2,
SpringMVCArchitecture–ArchitectingYourWebStore).Anyhow,Iwillrepeatitbriefly
here.
InternalResourceViewResolverwillresolvetheactualview’sfilepathbyprepending
theconfiguredprefixvalueandappendingthesuffixvaluewiththelogicalviewname;the
logicalviewnameisthevalueusuallyreturnedbythecontrollermethod.So,the
controllermethoddidn’treturnanyactualview;itjustreturnedtheviewname.Itisthe
jobofInternalResourceViewResolvertoformthecorrectURLpathofactualJSPview
fileforInternalResourceView.
Theredirectview
Inawebapplication,URLredirectionorforwardingarethetechniquestomovevisitorsto
adifferentwebpagethantheonetheyrequest.Mostofthetime,thistechniqueisused
aftersubmittingawebformtoavoidresubmissionofthesameformduetotheeventof
pressingthebrowser’sbackbuttonorrefreshbutton.SpringMVChasaspecialView
objectcalledRedirectviewtohandleredirectionandforwarding.TouseRedirectview
(org.springframework.web.servlet.view.Redirectview)withourcontroller,we
simplyneedtoreturnthetargetURLstringwiththeredirectionprefixfromthecontroller.
TherearetworedirectionprefixesavailableinSpringMVC,asshowninthefollowing
codesnippet:
returnredirect:/products/productDetail
And:
returnforward:/products/productDetail
Timeforaction–examiningRedirectView
Thoughbothredirectionandforwardingareusedtopresentadifferentwebpagethanthe
onerequested,thereisalittledifferencebetweenthem.Let’strytounderstandtheseby
examiningthem:
1. OpenourHomeControllerclassandaddonemorerequestmappingmethodas
follows:
@RequestMapping("/welcome/greeting")
publicStringgreeting(){
return"welcome";
}
2. Now,alterthereturnstatementoftheexistingwelcomerequestmappingmethod,
andsaveitasfollows:
return"forward:/welcome/greeting";
3. Now,runourapplicationandenterhttp://localhost:8080/webstore/.Youwillbe
abletoseeawelcomemessageonthewebpage.
4. Now,alterthereturnstatementoftheexistingwelcomerequestmappingmethod
againandsaveitasfollows:
return"redirect:/welcome/greeting";
5. Now,runourapplicationandenterhttp://localhost:8080/webstore/.Youwill
seeablankpagewithoutanywelcomemessage.
6. Finally,revertthereturnvalueofthewelcomemethodofHomeControllertothe
originalvalue,shownasfollows:
return"welcome";
Whatjusthappened?
So,whatwehavedemonstratedhereishowwecaninvoketheredirectviewfromthe
controllermethod.Instep1,wesimplycreatedarequestmappingmethodcalled
greetingforthewelcome/greetingrequestpath.Thismethodsimplyreturnsalogical
viewnameaswelcome.
Sincewereturnedthelogicalviewnameaswelcome,thewelcome.jspfilewillbe
renderedbyInternalResourceViewatruntime.Thewelcome.jspfileexpectstwomodel
attributes,namelygreetingandtagline,duringrendering.Instep2,wealteredthe
returnstatementoftheexitingrequestmappingmethodtoreturnaredirectedURL,as
follows:
@RequestMapping("/")
publicStringwelcome(Modelmodel){
model.addAttribute("greeting","WelcometoWebStore!");
model.addAttribute("tagline","Theoneandonlyamazingwebstore");
return"forward:/welcome/greeting";
}
Whatwehavedoneinstep2ismoreimportant;insteadofreturningalogicalviewname,
wesimplyreturntherequestpathvalueofthegreetinghandlermethodwiththe
forward:keywordprefixed.
ThemomentSpringMVCseesthis,itcanunderstandthatitisnotaregularlogicalview
name,soitwon’tsearchforanyviewfileunderthesrc/main/webapp/WEB-INF/views/
directory;rather,itwillconsiderthisrequestforittobeforwardedtoanotherrequest
mappingmethodbasedontherequestpathattachedaftertheforward:keyword.
Oneimportantthingtorememberhereisthattheforwardedrequestisstilltheactive
originalrequest,sowhatevervaluewehaveputinthemodelatthestartoftherequest
wouldstillbeavailable.ThisiswhywedidnotaddanyvaluetoModelinsidethe
greetingmethod.Wesimplyreturntheviewnameaswelcomeandthewelcome.jspfile
ontheassumptionthattherewillbemodelattributes,namelygreetingandtagline,
availableinthemodel.So,whenwefinallyrunourapplication,asmentionedinstep3,
eventhoughweissuedtherequesttotheURLhttp://localhost:8080/webstore/,the
RedirectViewwillforwardourrequestto
http://localhost:8080/webstore/welcome/greeting,andwewillabletoseethe
welcomemessageonthewebpage.
Againinstep4,wesimplychangedthereturnstatementofthewelcomemethodwiththe
redirect:prefix.Thistime,Springwillconsiderthisrequestasanewrequest,so
whatevervaluewehaveputinthemodel(insidethewelcomemethod)atthestartofthe
originalrequestwouldhavebeengone.Thisiswhyyousawanemptywelcomepagein
step6,sincethewelcome.jsppagecan’treadthegreetingandtaglinemodelattributes
fromthemodel.
So,basedonthisexercise,weunderstandthatRedirectViewwillgetintothepictureifwe
returnaredirectedURLwiththeappropriateprefixfromthecontrollermethod.
RedirectViewwillkeeptheoriginalrequestorspawnanewrequestbasedonredirection
orforwarding.
Popquiz–redirectview
Considerthefollowingcustomercontroller:
@Controller("/customers")
publicclassCustomerController{
@RequestMapping("/list")
publicStringlist(Modelmodel){
return"customers";
}
@RequestMapping("/process")
publicStringprocess(Modelmodel){
//return
}
}
Q1.IfIwanttogetredirectedtothelistmethodfromprocess,howshouldIformthe
returnstatementwithintheprocessmethod?
1. return"redirect:list";.
2. return"redirect:/list";.
3. return"redirect:customers/list";.
4. return"redirect:/customers/list";.
Servingstaticresources
Sofar,wehaveseenthateveryrequestgoesthroughthecontrollerandreturnsa
correspondingviewfilefortherequest;mostofthetime,theseviewfilescontaindynamic
content.Bydynamiccontent,Imeanthemodelvaluesthataredynamicallypopulatedin
theviewfileduringtherequestprocessing.Forexample,iftheviewfileisoftheJSPtype,
thenwepopulatemodelvaluesintheJSPfileusingtheJSPexpressionnotation,${}.
However,whatifwehavesomestaticcontentthatwewanttoservetotheclient?For
example,consideranimagethatisstaticcontent;wedon’twanttogothroughcontrollers
inordertoserve(fetch)animageasthereisnothingtoprocessorupdateanyvaluesinthe
model.Wesimplyneedtoreturntherequestedimage.
Let’ssaywehaveadirectory(/resources/images/)thatcontainssomeproductimages,
andwewanttoservetheseimagesuponrequest.Forexample,iftherequestedURLis
http://localhost:8080/webstore/resource/images/P1234.png,thenwewouldliketo
servetheimagewiththeP1234.pngname.Similarly,iftherequestedURLis
http://localhost:8080/webstore/resource/images/P1236.png,thenanimagewith
thenameP1236.pngneedstobeserved.
Timeforaction–servingstaticresources
Let’sseehowwecanservestaticimageswithSpringMVC:
1. Placesomeimagesunderthesrc/main/webapp/resources/images/directory;I
haveusedthreeproductimages,namelyP1234.png,P1235.png,andP1236.png.
2. Addthefollowingtaginourwebapplicationcontext’sconfiguration
DispatcherServlet-context.xmlfile:
<mvc:resourceslocation="/resources/"mapping="/resource/**"/>
3. Now,runourapplicationandenter
http://localhost:8080/webstore/resource/images/P1234.png(changethe
imagenameintheURLbasedontheimagesyouplacedinstep1).
4. Youarenowabletoviewtheimageyourequestedinthebrowser.
Whatjusthappened?
Whatjusthappenedwassimple;instep1,weplacedsomeimagefilesunderthe
src/main/webapp/resources/images/directory.Instep2,wejustaddedthe
<mvc:resources>taginthewebapplicationcontextconfigurationtotellSpringwhere
theseimagefilesarelocatedinourprojectsothatspringcanservethosefilesupon
request.Considerthefollowingcodesnippet:
<mvc:resourceslocation="/resources/"mapping="/resource/**"/>
Thelocationattributeofthe<mvc:resources>tagdefinesthebasedirectorylocationof
staticresourcesthatyouwanttoserve.Inourcase,wewanttoserveallimagesthatare
availableunderthesrc/main/webapp/resources/images/directory;youmaywonder
whywehavegivenonly/resources/asthelocationvalueinsteadof
src/main/webapp/resources/images/.Thisisbecauseweconsidertheresources
directoryasthebasedirectoryforallresources,wecanhavemultiplesubdirectoriesunder
resourcesdirectorytoputourimagesandotherstaticresourcefiles
Thesecondattribute,mapping,justindicatestherequestpaththatneedstobemappedto
thisresourcedirectory.Inourcase,wehaveassigned/resources/**asthemapping
value.So,ifanywebrequeststartswiththe/resourcerequestpath,thenitwillbe
mappedtotheresourcesdirectory,andthe/**symbolindicatestherecursivelookfor
anyresourcefilesunderneaththebaseresourcedirectory.
Thisiswhy,ifyounoticeinstep3,weformedtheURLas
http://localhost:8080/webstore/resource/images/P1234.png.So,whileservingthis
webrequest,SpringMVCwillconsider/resource/images/P1234.pngastherequest
path.So,itwilltrytomap/resourcetotheresourcebasedirectory,resources.Fromthis
directory,itwilltrytolookfortheremainingpathoftheURL,whichis
/images/P1234.png.Sincewehavetheimagesdirectoryundertheresourcesdirectory,
Springcaneasilylocatetheimagefilefromtheimagesdirectory.
Asamatteroffact,behindthescreen,SpringMVCuses
org.springframework.web.servlet.resource.ResourceHttpRequestHandlertoserve
theresourcesthatareconfiguredbythe<mvc:resources>tag.So,inourapplication,if
anyrequestcomeswiththerequestpath’s/resourceprefixinitsURL,thenSpringwill
lookintothelocationdirectorythatisconfiguredinthe<mvc:resources>tagandwill
returntherequestedfiletothebrowser.Remember,Springallowsyoutohostnotonly
images,butalsoanytypeofstaticfiles,suchasPDFs,Worddocuments,Excelsheets,and
sooninthisfashion.
Itisgoodthatweareabletoserveproductimageswithoutaddinganyextrarequest
mappingmethodsinthecontroller.
Popquiz–staticview
Considerthefollowingresourceconfiguration:
<mvc:resourceslocation="/pdf/"mapping="/resources/**"/>
Q1.Underthepdfdirectory,ifIhaveasubdirectorysuchasproduct/manuals/,which
containsa.pdffilecalledmanual-P1234.pdf,howcanIformtherequestpathtoaccess
that.pdffile?
1. /pdf/product/manuals/manual-P1234.pdf.
2. /resources/pdf/product/manuals/manual-P1234.pdf.
3. /product/manuals/manual-P1234.pdf.
4. /resource/pdf/product/manuals/manual-P1234.pdf.
Timeforaction–addingimagestothe
productdetailpage
Let’sextendthistechniquetoshowproductimagesinourproductlistingpageandinthe
productdetailpage.Performthefollowingsteps:
1. Openproducts.jsp;youcanfindproducts.jspunderthe/src/main/webapp/WEB-
INF/views/directoryinyourproject.Now,addthefollowing<img>tagafterthe
<divclass="thumbnail">tag:
<imgsrc="<c:urlvalue="/resource/images/${product.productId}.png">
</c:url>"alt="image"style="width:100%"/>
2. Similarly,openproduct.jspandaddthefollowing<img>tagafterthe<div
class="row">tag:
<divclass="col-md-5">
<imgsrc="<c:urlvalue="/resource/images/${product.productId}.png">
</c:url>"alt="image"style="width:100%"/>
</div>
3. Now,runourapplicationandenterhttp://localhost:8080/webstore/products.
Youwillbeabletoseetheproductlistpagewitheveryproductthathasaproduct
image,asshowninthefollowingfigure:
Productlistingswiththeimageattached
4. Now,clickontheDetailsbuttonofanyproduct,andyouwillbeabletoseethe
correspondingviewoftheproductdetailswiththeimageattachedtothedetailspage,
asfollows:
Theproductdetailpagewiththeimageattached
Whatjusthappened?
Whatwehavedoneissimple.Welearnedhowwecanservestaticresourcesandhowwe
canhostproductimages.Duringthisexercise,welearnedthatinourapplication,ifany
requestcomeswiththerequestpath’s/resourceprefix,itwouldgetmappedtothebase
resourcedirectory,andanyremainingURLpathwouldleadtothestaticfile.
Weleveragedthisfact,andformedtheimage’ssrcURLaccordingly;noticethesrc
attributeofthe<img>tagweaddedinstep1:
<imgsrc="<c:urlvalue="/resource/images/${product.productId}.png">
</c:url>"alt="image"style="width:100%"/>
Thesrcattributevaluethatweareforminginthepreceding<img>taghasanexpression
languagenotationtofetchtheproductID;aftergettingtheproductID,wesimply
concatenateittotheexistingvaluetoformavalidrequestpath,shownasfollows:
/resource/images/${product.productId}.png
Forexample,iftheproductIDisP1234,thenwewouldgetanimagerequestURLas
/resource/images/P1234.png,whichisnothingbutoneoftheimagefilenamesthatwe
havealreadyputupinthe/resources/imagesdirectory.So,Springcaneasilyreturnthe
imagefilethatweshowedusingthe<img>taginsteps1and2.
Themultipartrequestinaction
Intheprecedingexercise,welearnedhowwecanincorporatethestaticviewtoshow
productimagesintheproducts’detailspage.Wesimplyputsomeimagesinadirectoryin
theserverandperformedaconfiguration,andSpringMVCwasabletopickupthesefiles
duringtherenderingofthepagethathadtheproductdetails.Whatifweautomatethis
process?Imeaninsteadofputtingtheseimages,whatifweareabletouploadimagesto
theimagedirectory?
Howcanwedothis?Therecomesthemultipartrequest.Themultipartrequestisatypeof
HTTPrequestthatsendsthefileanddatatotheserver.SpringMVChasgoodsupportfor
amultipartrequest.Let’ssaywewanttouploadsomefilestotheserver.Toaccomplish
this,wewillhavetoformamultipartrequest.
Timeforaction–addingimagestothe
productpage
Let’saddtheimageuploadfacilitytoouraddproductspage:
1. Addabeandefinitioninourwebapplication’scontextconfigurationfile
(DispatcherServlet-context.xml)forCommonsMultipartResolver,asfollows:
<beanid="multipartResolver"
class="org.springframework.web.multipart.commons.CommonsMultipartResolv
er">
<propertyname="maxUploadSize"value="10240000"/>
</bean>
2. Openpom.xml;youcanfindpom.xmlundertheprojectrootdirectoryitself.
3. Youwillbeabletoseesometabsatthebottomofthepom.xmlfile.Selectthe
DependenciestabandclickontheAddbuttonoftheDependenciessection.
4. ASelectDependencywindowwillappear;enterGroupIdascommons-fileupload,
ArtifactIdascommons-fileupload,Versionas1.2.2;selectScopeascompile;and
clickontheOKbutton.
5. Similarly,addonemoreGroupIddependencyasorg.apache.commons,ArtifactId
ascommons-io,Versionas1.3.2;selectScopeascompile;clickontheOKbutton;
andsavethepom.xmlfile.
6. Openourproduct’sdomainclass(Product.java)andaddareferenceto
org.springframework.web.multipart.MultipartFilewiththecorresponding
settersandgettersasfollows:
privateMultipartFileproductImage;
7. OpenaddProduct.jsp;youcanfindaddProduct.jspunderthe
/src/main/webapp/WEB-INF/views/directoryinyourproject.Addthefollowingset
oftagsafterthe<form:inputid="condition">taggroup:
<divclass="form-group">
<labelclass="control-labelcol-lg-2"for="productImage">
<spring:messagecode="addProdcut.form.productImage.label"/></label>
<divclass="col-lg-10">
<form:inputid="productImage"path="productImage"type="file"
class="form:input-large"/>
</div>
</div>
8. Addanentryinourmessagebundlesource(messages.properties)fortheproduct’s
imagelabel,asfollows:
addProdcut.form.productImage.label=ProductImagefile
9. Now,settheenctypeattributetomultipart/form-dataintheformtagasfollows
andsaveaddProduct.jsp:
<form:formmodelAttribute="newProduct"class="form-
horizontal"enctype="multipart/form-data">
10. OpenourProductController.javafileandmodifytheprocessAddNewProductForm
method’ssignaturebyaddinganextramethodparameteroftheHttpServletRequest
type(javax.servlet.http.HttpServletRequest);sobasically,your
processAddNewProductFormmethodsignatureshouldlooklikethefollowingcode
snippet:
publicStringprocessAddNewProductForm(@ModelAttribute("newProduct")
ProductnewProduct,BindingResultresult,HttpServletRequestrequest){
11. AddthefollowingcodesnippetinsidetheprocessAddNewProductFormmethodjust
beforeproductService.addProduct(newProduct);:
MultipartFileproductImage=productToBeAdded.getProductImage();
StringrootDirectory
=request.getSession().getServletContext().getRealPath("/");
if(productImage!=null&&!productImage.isEmpty()){
try{

productImage.transferTo(newFile(rootDirectory+"resources\\images\\"+pro
ductToBeAdded.getProductId()+".png"));
}catch(Exceptione){
thrownewRuntimeException("ProductImagesavingfailed",e);
}
}
12. WithintheinitialiseBindermethod,addtheproductImagefieldtothewhitelisting
setasfollows:
binder.setAllowedFields("productId","name","unitPrice","description","m
anufacturer","category","unitsInStock","productImage");
13. Now,runourapplicationandentertheURL
http://localhost:8080/webstore/products/add.Youwillbeabletoseeouradd
productspagewithanextrainputfieldtochooseafiletoupload.Justfillevery
informationasusualandmoreimportantly,chooseanimagefileofyourchoiceto
addanewimagefile,andclickontheAddbutton.Youwillthenbeabletoseethat
theimagehasbeenaddedtotheproductspageandtheproductdetailspage,asshown
inthefollowingscreenshot:
Addproductpagewithimageselectionoption
Whatjusthappened?
Spring’sCommonsMultipartResolver
(org.springframework.web.multipart.commons.CommonsMultipartResolver)class
determineswhetherthegivenrequestcontainsmultipartcontentornotandparsesthe
givenHTTPrequestintomultipartfilesandparameters.Thisiswhyweinitiatedthisclass
withinourservletcontextinstep1.ThroughthemaxUploadSizeproperty,wehaveseta
maximumof10240000bytesastheallowedfilesizetobeuploaded:
<bean
id="multipartResolver"class="org.springframework.web.multipart.commons.Comm
onsMultipartResolver">
<propertyname="maxUploadSize"value="10240000"/>
</bean>
Fromsteps2to5,weaddedsomeoftheorg.apache.commonslibrariesasourmaven
dependency.ThisisbecauseSpringusestheselibrariesinternallytosupportthefile
uploadingfeature.
Sincetheimagethatwewereuploadingbelongstoaproduct,itisbettertokeepthat
imageaspartoftheproductinformation;thisiswhyinstep6,weaddedareferenceto
MultipartFileinourdomainclass(Product.java)andaddedcorrespondingsettersand
getters.ThisMultipartFilereferenceholdstheactualproductimagefilethatwewere
uploading.
Wewanttoincorporatetheimageuploadingfacilityinouraddproductspage;thisiswhy,
intheaddProduct.jspviewfile,weaddedafileinputtagtochoosethedesiredimage,
shownasfollows:
<divclass="form-group">
<labelclass="control-labelcol-lg-2"for="productImage"><spring:message
code="addProdcut.form.productImage.label"/>
</label>
<divclass="col-lg-10">
<form:inputid="productImage"path="productImage"type="file"
class="form:input-large"/>
</div>
</div>
Intheprecedingsetoftag,theimportantoneisthe<form:input>tag.Ithasthetype
attributeasfilesothatitcanhavetheChooseFilebuttontodisplaythefilechooser
window.Asusual,wewantthisformfieldtobeboundwiththedomainobjectfield;thisis
whywehavesetthepathattributeasproductImage.Ifyouremembercorrectly,this
pathnameisnothingbutthesameMultipartFilereferencenamethatweaddedinstep6.
Asusual,wewanttoexternalizethelabelmessageforthisfileinputtagaswell,andthat’s
whyweaddedthe<spring:message>tag,andinstep8,weaddedthecorresponding
messageentryinthemessagesourcefile(messages.properties).
Sinceouraddproductformisnowcapableofsendingimagefilesaswellaspartofthe
request,weneedtoencodetherequestasamultipartrequest.Thisiswhy,instep9,we
addedtheenctypeattributetothe<form:form>tagandsetitsvalueasmultipart/form-
data.Theenctypeattributeindicateshowtheformdatashouldbeencodedwhenweare
submittingittotheserver.
Wewantedtosavetheimagefileintheserverunderthelocation’sresources/images
directory;thisdirectorystructurewouldbeavailabledirectlyundertherootdirectoryof
ourwebapplicationatruntime.So,inordertogettherootdirectoryofourweb
application,weneedHttpServletRequest.Seethefollowingcodesnippet:
StringrootDirectory=
request.getSession().getServletContext().getRealPath("/");
Thisiswhyweaddedanextramethodparametercalledrequestofthe
HttpServletRequesttypetoourprocessAddNewProductFormmethodinstep10.
Remember,SpringwillfillthisrequestparameterwiththeactualHTTPrequest.
Instep11,wesimplyreadtheimagefilefromthedomainobjectandwroteitintoanew
filewiththeproductIDasthename,asshowninthefollowingcodesnippet:
MultipartFileproductImage=productToBeAdded.getProductImage();
StringrootDirectory=
request.getSession().getServletContext().getRealPath("/");
if(productImage!=null&&!productImage.isEmpty()){
try{
productImage.transferTo(new
File(rootDirectory+"resources\\images\\"+
productToBeAdded.getProductId()+".png"));
}catch(Exceptione){
thrownewRuntimeException("ProductImagesavingfailed",e);
}
}
Remember,wepurposelysavetheimageswiththeproductIDnamebecausewehave
alreadydesignedourproducts(products.jsp)pageanddetail(product.jsp)page
accordinglyinordertodisplaytherightimagebasedontheproductID.
Asafinalstep,weaddedthenewlyintroducedproductImagefiletothewhitelistingsetin
thebinderconfigurationwithintheinitialiseBindermethod.
Now,ifyourunourapplicationandenter
http://localhost:8080/webstore/products/add,youwillbeabletoseeouradd
productspagewithanextrainputfieldtochoosethefiletoupload.
Haveagohero–uploadingproductusermanuals
totheserver
Itisnicethatwewereabletouploadtheproductimagetotheserverwhileaddinganew
product.Whydon’tyouextendthisfacilitytouploadaPDFfiletoserver?Forexample,
considerthateveryproducthasausermanualandyouwanttouploadtheseusermanuals
aswellwhileaddingaproduct.
HerearesomeofthethingsyoucandotouploadPDFfiles:
Createadirectorywiththepdfnameunderthesrc/main/webapp/resources/
directoryinyourproject.
AddonemoreMultipartFilereferenceinyourproductdomainclass
(Product.java)toholdthePDFfileandchangeProduct.javaaccordingly.
ExtendaddProduct.jsp.
ExtendProductController.javaaccordingly;don’tforgettoaddthenewlyadded
fieldtothewhitelist.
Sofinally,youwillbeabletoaccessthePDFunder
http://localhost:8080/webstore/resource/pdf/P1237.pdfifthenewlyadded
productidisP1237.Goodluck!
UsingContentNegotiatingViewResolver
Contentnegotiationisamechanismthatmakesitpossibletoserveadifferent
representationofthesameresource.Forexample,sofarwehavedisplayedourproduct
detailpageinaJSPrepresentation.Whatifwewanttorepresentthesamecontentinan
XMLformat,andsimilarly,whatifwewantthesamecontentinaJSONformat?There
comesSpringMVC’sContentNegotiatingViewResolver
(org.springframework.web.servlet.view.ContentNegotiatingViewResolver)tohelp
us.TheXMLandJSONformatsarepopulardatainterchangeformatsthatareusedinweb
servicecommunicationsheavily.So,usingContentNegotiatingViewResolver,wecan
incorporatemanyviewssuchasMappingJacksonJsonView(forJSON)and
MarshallingView(forXML)torepresentthesameproductinformationasthe
XML/JSONformat.
Timeforaction–configuring
ContentNegotiatingViewResolver
ContentNegotiatingViewResolverdoesnotresolveviewsitselfbutdelegatesthemto
otherviewresolversbasedontherequest.Now,let’saddthecontentnegotiationcapability
toourapplication:
1. Openpom.xml;youcanfindpom.xmlundertheprojectrootdirectoryitself.
2. Youwillbeabletoseesometabsatthebottomofpom.xmlfile.Selectthe
DependenciestabandclickontheAddbuttonoftheDependenciessection.
3. ASelectDependencywindowwillappear;enterGroupIdas
org.springframework,ArtifactIdasspring-oxm,Versionas4.0.3.RELEASE;
selectScopeascompile;andthenclickontheOKbutton.
4. Similarly,addonemoredependencyGroupIdasorg.codehaus.jackson,Artifact
Idasjackson-mapper-asl,Versionas1.9.10,andselectScopeascompile.Then,
clickontheOKbuttonandsavepom.xml.
5. AddthebeanconfigurationforContentNegotiatingViewResolverinourweb
application’scontextconfigurationfile,DispatcherServlet-context.xml,as
follows:
<bean
class="org.springframework.web.servlet.view.ContentNegotiatingViewResol
ver">
<propertyname="defaultViews">
<list>
<refbean="jsonView"/>
<refbean="xmlView"/>
</list>
</property>
</bean>
6. Now,addthebeanconfigurationfortheJSONviewasfollows:
<beanid="jsonView"
class="org.springframework.web.servlet.view.json.MappingJacksonJsonView
">
<propertyname="prettyPrint"value="true"/>
</bean>
7. Finally,addthebeanconfigurationfortheXMLviewasfollows:
<beanid="xmlView"
class="org.springframework.web.servlet.view.xml.MarshallingView">
<constructor-arg>
<beanclass="org.springframework.oxm.jaxb.Jaxb2Marshaller">
<propertyname="classesToBeBound">
<list>
<value>com.packt.webstore.domain.Product</value>
</list>
</property>
</bean>
</constructor-arg>
</bean>
8. Openourproductdomainclass(Product.java),andaddthe@XmlRootElement
annotationatthetopoftheclass.
9. Similarly,addthe@XmlTransientannotationatthetopofthegetProductImage()
methodandaddanother@JsonIgnoreannotationontopoftheproudctImagefield.
10. Now,runourapplicationandenter
http://localhost:8080/webstore/products/product?id=P1234.Youwillnowbe
abletoviewthedetailpageoftheproductwiththeP1234ID.
11. NowchangetheURLwiththe.xmlextension
(http://localhost:8080/webstore/products/product.xml?id=P1234).Youwill
beabletoseethesamecontentintheXMLformat,asshowninthefollowing
screenshot:
TheproductdetailpagethatshowstheproductinformationintheXMLformat
12. Similarly,thistimechangetheURLwiththe.jsonextension
(http://localhost:8080/webstore/products/product.json?id=P1234).Youwill
beabletoseetheJSONrepresentationofthatcontentasshowninthefollowing
screenshot:
TheproductdetailpagethatshowstheproductinformationintheJSONformat
Whatjusthappened?
SincewewantanXMLrepresentationforourmodeldatatoconvertourmodelobjects
intoXML,weneedSpring’sobject/XMLmappingsupport.Thisiswhyweaddedthe
dependencyforspring-oxm.jarinsteps1to3.Thespring-oxmnotationwillhelpus
convertanXMLdocumenttoandfromaJavaobject.
Similarly,toconvertmodelobjectsintoJSON,SpringMVCwillusejackson-mapper-
asl.jar,soweneedthatJARinourprojectaswell.Instep4,wejustaddedthe
dependencyconfigurationforthatjar.
Ifyouremember,wehavealreadydefinedInternalResourceViewResolverinourweb
applicationcontextasourviewresolvertoresolveJSP-basedviews.However,thistime,
wewantaviewresolvertoresolveXMLandJSONviews.Thisiswhy,instep6and7,we
configuredMappingJacksonJsonView(forJSON)andMarshallingView(forXML)inour
webapplicationcontext.
AsIalreadymentioned,ContentNegotiatingViewResolverdoesnotresolveviewsitself.
Instead,itdelegatestootherviewsbasedontherequest,soweneedtointroduceother
viewstoContentNegotiatingViewResolver.Wedidthatinstep5throughthe
defaultViewspropertyinContentNegotiatingViewResolver.Notethatinthe
ContentNegotiatingViewResolverbeanconfiguration,wejustaddedthebeanreference
fortheJSONviewandXMLviewunderthedefaultViewsproperty:
<bean
class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver"
>
<propertyname="defaultViews">
<list>
<refbean="jsonView"/>
<refbean="xmlView"/>
</list>
</property>
</bean>
WeconfiguredbeanreferencesforjsonViewandxmlViewinside
ContentNegotiatingViewResolver.
ThexmlViewbeanconfiguration,especially,hasoneimportantpropertycalled
classesToBeBound,whichliststhedomainobjectsthatneedsXMLconversionduringthe
requestprocessing.SinceourproductdomainobjectneedstheXMLconversion,weadded
com.packt.webstore.domain.ProductinthelistofclassesToBeBound,shownas
follows:
<beanid="xmlView"
class="org.springframework.web.servlet.view.xml.MarshallingView">
<constructor-arg>
<beanclass="org.springframework.oxm.jaxb.Jaxb2Marshaller">
<propertyname="classesToBeBound">
<list>
<value>
com.packt.webstore.domain.Product
</value>
</list>
</property>
</bean>
</constructor-arg>
</bean>
InordertoconverttoXML,weneedtogiveonemorehinttoMarshallingViewto
identifytherootXMLelementintheProductdomainobject.Thisiswhy,instep8,we
annotatedourclasswiththe@XmlRootElementannotation
(javax.xml.bind.annotation.XmlRootElement).
Instep9,weaddedthe@XmlTransientannotation
(javax.xml.bind.annotation.XmlTransient)ontopofthegetProductImage()method
andaddedanotherannotation,@JsonIgnore
(org.codehaus.jackson.annotate.JsonIgnore),ontopoftheproductImagefield.This
isbecausewedon’twanttorepresenttheproductimageaspartoftheXMLvieworJSON
view.Sincebothformatsarepurelytext-basedrepresentation,itisnotpossibleto
representimagesintexts.
Instep10,wesimplyaccessedourproductdetailpageinaregularwaybyfiringtheweb
requesthttp://localhost:8080/webstore/products/product?id=P1234fromthe
browser,andwewillbeabletoseethenormalJSPview,asexpected.
Instep11,wejustchangedtheURLslightlybyaddinga.xmlextensiontothe
http://localhost:8080/webstore/products/product.xml?id=P1234requestpath.
Thistime,wewillbeabletoseethesameproductinformationintheXMLformat.
Similarly,fortheJSONview,wechangedtheextensionbyadding.jsontothe
http://localhost:8080/webstore/products/product.json?id=P1234path,andwe
willbeabletoseetheJSONrepresentationofthesameproductinformation.
Workingwiththehandlerexception
resolver
SpringMVCprovidesseveralapproachestoexceptionhandling.InSpring,oneofthe
mainexceptionhandlingconstructsistheHandlerExceptionResolverinterface
(org.springframework.web.servlet.HandlerExceptionResolver).Anyobjectsthat
implementthisinterfacecanresolveexceptionsthatarethrownduringcontrollermapping
orexecution.TheHandlerExceptionResolverimplementersaretypicallyregisteredas
beansinthewebapplicationcontext.
SpringMVCcreatestwosuchHandlerExceptionResolverimplementationsbydefaultto
facilitateexceptionhandling:
ResponseStatusExceptionResolveriscreatedtosupportthe@ResponseStatus
annotation
ExceptionHandlerExceptionResolveriscreatedtosupportthe@ExceptionHandler
annotation
Timeforaction–addingtheresponse
statusexception
First,wewilllookatthe@ResponseStatusannotation
(org.springframework.web.bind.annotation.ResponseStatus).InChapter3,Control
YourStorewithControllers,wecreatedarequestmappingmethodtodisplayproductsby
categoryundertheURItemplate,
http://localhost:8080/webstore/products/{category}.Ifnoproductswerefound
underthegivencategory,wewouldshowanemptywebpage,whichisnotcorrect
semantically.WeshouldshowanHTTPstatuserrortoindicatethatnoproductsexist
underthegivencategory.Let’sseehowwecandothatwiththehelpofthe
@ResponseStatusannotation:
1. CreateaclasscalledNoProductsFoundUnderCategoryExceptionunderthe
com.packt.webstore.exceptionpackageinthesourcefolder,src/main/java.Now
addthefollowingcodeintoit:
packagecom.packt.webstore.exception;
importorg.springframework.http.HttpStatus;
importorg.springframework.web.bind.annotation.ResponseStatus;
@ResponseStatus(value=HttpStatus.NOT_FOUND,reason="Noproductsfound
underthiscategory")
publicclassNoProductsFoundUnderCategoryExceptionextends
RuntimeException{
privatestaticfinallongserialVersionUID=3935230281455340039L;
}
2. Now,openourProductControllerclassandmodifythegetProductsByCategory
methodasfollows:
@RequestMapping("/{category}")
publicStringgetProductsByCategory(Model
model,@PathVariable("category")Stringcategory){
List<Product>products
=productService.getProductsByCategory(category);
if(products==null||products.isEmpty()){
thrownewNoProductsFoundUnderCategoryException();
}
model.addAttribute("products",products);
return"products";
}
3. Nowrunourapplicationandenter
http://localhost:8080/webstore/products/HeadPhones.YouwillseeanHTTP
statuserrorthatsaysNoproductsfoundunderthiscategory,shownasfollows:
TheproductcategorypagethatshowsHTTPStatus404for“Noproductsfound
underthiscategory”
Whatjusthappened?
Instep1,wejustcreatedaruntimeexceptioncalled
NoProductsFoundUnderCategoryExceptiontoindicatenoproductsfoundunderthegiven
category.Oneoftheimportantconstructsthatneedtobenoticedinthe
NoProductsFoundUnderCategoryExceptionclassisthe@ResponseStatusannotation,
whichinstructstheSpringMVCtoreturnaspecificHTTPstatusifthisexceptionhas
beenthrownfromarequest-mappingmethod.
WecanconfiguretheHTTPstatusthatneedstobereturnedviathevalueattributeofthe
@ResponseStatusannotation;inourcase,weconfiguredHttpStatus.NOT_FOUND
(org.springframework.http.HttpStatus),whichindicatesthefamiliarHTTP404
response.Thesecondattribute,reason,denotesthereasontobeusedfortheHTTP
responseerror.
Instep2,wejustmodifiedthegetProductsByCategorymethodinthe
ProductControllerclasstocheckwhethertheproductlistforthegivencategoryis
empty.Ifso,wesimplythrowtheexceptionwecreatedinstep1,whichcausestheHTTP
404statuserrortoreturntotheclientsayingNoproductsfoundunderthiscategory.
Sofinally,instep3,wefiredthewebrequest,
http://localhost:8080/webstore/products/HeadPhones,whichwouldtrytolookfor
productsundertheHeadPhonescategory,butsincewedidn’thaveanyproductsunderthe
HeadPhonescategory,wegottheHTTP404statuserror.
ItisgoodthatwehaveshowntheHTTPstatuserrorforproductsnotfoundunderagiven
category,butsometimes,youmaywishtohaveanerrorpagewhereyouwanttoshow
yourerrormessageinadetailedmanner.
Forexample,runourapplicationandenterthe
http://localhost:8080/webstore/products/product?id=P1234URL.Youwillbeable
toseeadetailedviewofIphone5s;now,changetheproductIDintheURLtoaninvalid
onesuchashttp://localhost:8080/webstore/products/product?id=P1000.Youwill
seeanerrorpage.
Timeforaction–addinganexception
handler
Wemustshowaniceerrormessagethatsaysthatnoproductswerefoundwiththegiven
productID.Let’sdothatwiththehelpof@ExceptionHandler:
1. CreateaclasscalledProductNotFoundExceptionunderthe
com.packt.webstore.exceptionpackageinthesourcefoldersrc/main/java.Now,
addthefollowingcodetoit:
packagecom.packt.webstore.exception;
publicclassProductNotFoundExceptionextendsRuntimeException{
privatestaticfinallongserialVersionUID=-694354952032299587L;
privateStringproductId;
publicProductNotFoundException(StringproductId){
this.productId=productId;
}
publicStringgetProductId(){
returnproductId;
}
}
2. Now,openourInMemoryProductRepositoryclassandmodifythegetProductById
methodasfollows:
publicProductgetProductById(StringproductId){
ProductproductById=null;

for(Productproduct:listOfProducts){
if(product!=null&&product.getProductId()!=null
&&product.getProductId().equals(productId)){
productById=product;
break;
}
}

if(productById==null){
thrownewProductNotFoundException("Noproductsfoundwiththe
productid:"+productId);
}

returnproductById;
}
3. Addanexceptionhandlermethodwiththe@ExceptionHandlerannotation
(org.springframework.web.bind.annotation.ExceptionHandler)asshowninthe
ProductControllerclass:
@ExceptionHandler(ProductNotFoundException.class)
publicModelAndViewhandleError(HttpServletRequest
req,ProductNotFoundExceptionexception){
ModelAndViewmav=newModelAndView();
mav.addObject("invalidProductId",exception.getProductId());
mav.addObject("exception",exception);
mav.addObject("url",req.getRequestURL()+"?"+req.getQueryString());
mav.setViewName("productNotFound");
returnmav;
}
4. Finally,addonemoreJSPviewfilecalledproductNotFound.jsp,underthe
src/main/webapp/WEB-INF/views/directoryandaddthefollowingcodesnippetsto
itandsaveit:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
<html>
<head>
<metahttp-equiv="Content-Type"content="text/htmlcharset=ISO-8859-
1">
<link
rel="stylesheet"href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/boo
tstrap.min.css">
<title>Welcome</title>
</head>
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1class="alertalert-danger">Thereisnoproductfound
withtheProductid${invalidProductId}</h1>
</div>
</div>
</section>
<section>
<divclass="container">
<p>${url}</p>
<p>${exception}</p>
</div>
<divclass="container">
<p>
<ahref="<spring:urlvalue="/products"/>"class="btnbtn-
primary">
<spanclass="glyphicon-hand-leftglyphicon"></span>
products
</a>
</p>
</div>
</section>
</body>
</html>
5. Now,runourapplicationandenter
http://localhost:8080/webstore/products/product?id=P1000.Youwillseean
errorpagethatsaysThereisnoproductfoundwiththeProductidP1000,shown
asfollows:
Aproductdetailpagethatshowsthecustomerrorpagefortheinvalidproductid
P1000
Whatjusthappened?
Wethoughtofshowingacustom-madeerrorpageinsteadofarawexceptionincasethe
productisnotfoundinthegivenproductID.So,inordertoachievethisinstep1,wejust
createdaruntimeexceptioncalledProductNotFoundExceptiontobethrownwhenthe
producthasnotbeenfoundforthegivenproductID.
Instep2,wejustmodifiedthegetProductByIdmethodofthe
InMemoryProductRepositoryclasstocheckwhetheranyproductswerefoundforthe
givenproductID.Ifnot,wesimplythrowtheexception(ProductNotFoundException)we
createdinstep1.
Instep3,weaddedourexceptionhandlermethodtohandleProductNotFoundException
withthehelpofthe@ExceptionHandlerannotation.WithinthehandleErrormethod,we
justcreatedaModelAndViewobject(org.springframework.web.servlet.ModelAndView)
andstoredtherequestedinvalidproductID,exception,andrequestedURL,andreturnedit
withtheviewname,productNotFound:
@ExceptionHandler(ProductNotFoundException.class)
publicModelAndViewhandleError(HttpServletRequest
req,ProductNotFoundExceptionexception){
ModelAndViewmav=newModelAndView();
mav.addObject("invalidProductId",exception.getProductId());
mav.addObject("exception",exception);
mav.addObject("url",req.getRequestURL()+"?"+req.getQueryString());
mav.setViewName("productNotFound");
returnmav;
}
SincewereturnedtheModelAndViewobjectwiththeproductNotFoundviewname,we
musthaveaviewfilewiththeproductNotFoundname.Thisiswhywecreatedsucha
viewfile(productNotFound.jsp)instep4.TheproductNotFound.jspfilejustcontainsa
CSS-styled<h1>tagtoshowtheerrormessageandalinkbuttontotheproductlisting
page.
So,wheneverwerequestedtoshowaproductwithaninvalidIDsuchas
http://localhost:8080/webstore/products/product?id=P1000,the
ProductControllerclasswouldthrowProductNotFoundException,whichwillbe
handledbythehandleErrormethodtoshowthecustomerrorpage
(productNotFound.jsp).
Summary
Inthischapter,welearnedhowInternalResourceViewResolverresolvesviews,andwe
learnedhowwecankickRedirectViewfromacontrollermethod.Welearnedthe
importantdifferencebetweenredirectandforward.Afterthat,welearnedhowwecan
hoststaticresourcefileswithoutgoingthroughthecontrollers’configuration.Wealso
learnedhowtoattachastaticimagefilewiththeproductdetailspage.Welearnedhowwe
canuploadfilestoserver.Finally,wesawhowwecanconfigure
ContentNegotiatingViewResolvertogivealternateXMLandJSONviewsforthe
productdomainobjectinourapplication.Finally,welearnedhowwecanmakeuseof
HandlerExceptionResolvertoresolveanexception.
Inthenextchapter,wewilllearnhowwecaninterceptregularwebrequestswiththehelp
ofaninterceptor.Seeyouinnextchapter!
Chapter6.InterceptYourStorewith
Interceptor
Inallthepreviouschapters,wehaveonlylearnedhowtomaparequesttoacontroller
method.Oncetherequestreachesthecontrollermethod,weexecutesomelogicandreturn
alogicalviewnamethatcanbeusedbytheviewresolvertoresolveviews.However,what
ifwewanttoexecutesomelogicbeforetheactualrequestprocessisperformed?Similarly,
whatifwewanttoexecuteanotherinstructionbeforedispatchingtheresponse?
TheSpringMVCinterceptorcanbeusedtointercepttheactualrequestandresponse.
Interceptorsareaspecialwebprogrammingtechniquewhereonecanexecuteacertain
pieceoflogicbeforeorafterawebrequestisprocessed.Inthischapter,wearegoingto
learnmoreabouttheinterceptor.Wewilllearnthefollowing:
Howtoconfigureaninterceptor
Howtoaddinternalizationsupport
Dataauditingusinganinterceptor
Conditionalredirectingusinganinterceptor
Workingwithinterceptors
AsIalreadymentioned,interceptorsareusedtointerceptactualwebrequestsbeforeor
aftertheyareprocessed.Wecanrelatetheinterceptor’sconceptinSpringMVCwiththe
filterconceptofservletprogramming.InSpringMVC,interceptorsarethespecialclasses
thatmustimplementtheorg.springframework.web.servlet.HandlerInterceptor
interface.
TheHandlerInterceptorinterfacedefinesthreeimportantmethods,asfollows:
preHandle:Thismethodgetscalledjustbeforethewebrequestreachesthecontroller
methodtobeexecuted
postHandle:Thismethodwillgetcalledjustaftertheexecutionofthecontroller
method
afterCompletion:Thismethodwillgetcalledafterthecompletionoftheentireweb
requestcycle
OncewehavecreatedourowninterceptorbyimplementingtheHandlerInterceptor
interface,weneedtoconfigureitinourwebapplicationcontextforittotakeeffect.
Timeforaction–configuringan
interceptor
Everywebrequesttakesacertainamountoftimetogetprocessedintheserver.Inorderto
findouthowmuchtimeittakestoprocessawebrequest,weneedtocalculatethetime
differencebetweenthestarttimeandendtimeofthewebrequestprocess.Wecanachieve
thisusingtheinterceptorconcept.Let’sconfigureourowninterceptorinourprojecttolog
theexecutiontimeofeachwebrequestbyperformingthefollowingsteps:
1. Openpom.xml—youcanfindpom.xmlundertherootdirectoryoftheprojectitself.
2. Youwillbeabletoseesometabsatthebottomofthepom.xmlfile;selectthe
DependenciestabandclickontheAddbuttonoftheDependenciessection.
3. ASelectDependencywindowwillappear;enterGroupIdaslog4j,enterArtifact
Idaslog4j,enterVersionas1.2.12,selectScopeascompile,andclickontheOK
buttontosavepom.xml.
4. CreateaclassnamedPerformanceMonitorInterceptorunderthe
com.packt.webstore.interceptorpackageinthesourcefoldersrc/main/javaand
addthefollowingcodeintoit:
packagecom.packt.webstore.interceptor;
importjava.text.DateFormat;
importjava.text.SimpleDateFormat;
importjava.util.Calendar;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
importorg.apache.log4j.Logger;
importorg.springframework.util.StopWatch;
importorg.springframework.web.servlet.HandlerInterceptor;
importorg.springframework.web.servlet.ModelAndView;
publicclassPerformanceMonitorInterceptorimplements
HandlerInterceptor{
ThreadLocal<StopWatch>stopWatchLocal=newThreadLocal<StopWatch>();
Loggerlogger=Logger.getLogger(this.getClass());
publicbooleanpreHandle(HttpServletRequest
request,HttpServletResponseresponse,Objecthandler)throwsException{
StopWatchstopWatch=newStopWatch(handler.toString());
stopWatch.start(handler.toString());
stopWatchLocal.set(stopWatch);
logger.info("AccessingURLpath:"+getURLPath(request));
logger.info("Requestprocessingstartedon:"+getCurrentTime());
returntrue;
}
publicvoidpostHandle(HttpServletRequestarg0,HttpServletResponse
response,Objecthandler,ModelAndViewmodelAndView)throwsException{
logger.info("Requestprocessingendedon"+getCurrentTime());
}
publicvoidafterCompletion(HttpServletRequest
request,HttpServletResponseresponse,Objecthandler,Exception
exception)throwsException{
StopWatchstopWatch=stopWatchLocal.get();
stopWatch.stop();
logger.info("Totaltimetakenforprocessing:"
+stopWatch.getTotalTimeMillis()+"ms");
stopWatchLocal.set(null);

logger.info("=======================================================");
}
privateStringgetURLPath(HttpServletRequestrequest){
StringcurrentPath=request.getRequestURI();
StringqueryString=request.getQueryString();
queryString=queryString==null?"":"?"+queryString;
returncurrentPath+queryString;
}
privateStringgetCurrentTime(){
DateFormatformatter=newSimpleDateFormat("dd/MM/yyyy'at'
hh:mm:ss");
Calendarcalendar=Calendar.getInstance();
calendar.setTimeInMillis(System.currentTimeMillis());
returnformatter.format(calendar.getTime());
}
}
5. Now,openthewebapplicationcontextconfigurationfileDispatcherServlet-
context.xmlfromsrc/main/webapp/WEB-INF/spring/webcontext/,andaddthe
followingelementinitandsavethefile:
<mvc:interceptors>
<bean
class="com.packt.webstore.interceptor.PerformanceMonitorInterceptor"/>
</mvc:interceptors>
6. Createapropertyfilenamedlog4j.propertiesunderthedirectory
src/main/resourcesandaddthefollowingcontenttoit.Then,savethefile:
#Rootloggeroption
log4j.rootLogger=INFO,file,stdout
#Directlogmessagestoalogfile
log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.File=C:\\webstore\\webstore-performance.log
log4j.appender.file.MaxFileSize=1MB
log4j.appender.file.MaxBackupIndex=1
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-ddHH:mm:ss}
%-5p%c{1}:%L-%m%n
#Directlogmessagestostdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{yyyy-MM-ddHH:mm:ss}
%-5p%c{1}:%L-%m%n
7. Now,runtheapplicationandenterhttp://localhost:8080/webstore/products.
Youwillbeabletoseetheperformanceloggingintheconsoleasfollows:
ThePerformanceMonitorInterceptorloggingmessageisshownintheconsole
8. JustopenC:\webstore-performance.log;youwillseethesamelogmessageinthe
loggingfileaswell.
Whatjusthappened?
Ourintentionwastorecordtheexecutiontimeofeveryrequestthatisbeingreceivedby
ourwebapplication;wedecidedtorecordtheexecutiontimeinalogfile.So,inorderto
usealogger,weneedthelog4jlibrary;weaddedthelog4jlibraryasamaven
dependencyinstep3.
Instep4,wejustdefinedaninterceptorclassnamedPerformanceMonitorInterceptor
byimplementingtheHandlerInterceptorinterface.Asmentionedpreviously,thereare
threemethodsthatneedtobeimplemented.Wewillseeeachmethodonebyone.Thefirst
methodispreHandle(),whichiscalledbeforetheexecutionofthecontrollermethod:
publicbooleanpreHandle(HttpServletRequestrequest,HttpServletResponse
response,Objecthandler)throwsException{
StopWatchstopWatch=newStopWatch(handler.toString());
stopWatch.start(handler.toString());
stopWatchLocal.set(stopWatch);
logger.info("AccessingURLpath:"+getURLPath(request));
logger.info("Requestprocessingstartedon:"+getCurrentTime());
returntrue;
}
IntheprecedingpreHandlemethod,wejustinitiatedaStopWatchclasstostartrecording
thetime.Inthenextstep,weputthatstopWatchinstanceinaThreadLocalvariablecalled
thestopWatchLocalforthepurposeofretrievallateron.
Note
JavaprovidesaThreadLocalclassthatwecanset/getthreadscopedvariables.Thevalues
storedinThreadLocalarelocaltothethread,whichmeansthateachthreadwillhaveits
ownThreadLocalvariable.Onethreadcannotaccess/modifytheThreadLocalvariables
ofotherthreads.SinceSpringMVCisbasedontheservletprogrammingmodel,eachweb
requestisanindividualthread.
Finally,wejustloggedtherequestedURLpathandcurrentservertimewiththehelpof
logger.Therefore,wheneverarequestcomestoourwebapplication,itisfirstreceived
throughthispreHandlemethodandinitiatesstopWatchbeforereachingthecontroller
method.
ThesecondmethodispostHandle,whichwillgetcalledaftertheexecutionofthe
controllermethod:
publicvoidpostHandle(HttpServletRequestarg0,HttpServletResponse
response,Objecthandler,ModelAndViewmodelAndView)throwsException{
logger.info("Requestprocessingendedon"+getCurrentTime());
}
Intheprecedingmethod,wesimplylogthecurrenttime,whichisconsideredtherequest
processingfinishedtime.OurfinalmethodisafterCompletion,whichiscalledafterthe
completerequesthasbeenprocessed:
publicvoidafterCompletion(HttpServletRequestrequest,HttpServletResponse
response,Objecthandler,Exceptionexception)throwsException{
StopWatchstopWatch=stopWatchLocal.get();
stopWatch.stop();
logger.info("Totaltimetakenforprocessing:"
+stopWatch.getTotalTimeMillis()+"ms");
stopWatchLocal.set(null);
logger.info("=======================================================");
}
IntheafterCompletionmethod,weretrievedthestopwatchinstancefromThreadLocal
andimmediatelystoppedit;now,thestopwatchinstancewillhavearecordofthetotal
timethatwastakenbetweenthepreHandleandafterCompletionmethods,whichis
consideredasthetotaltimetakentocompletearequest.Wesimplyloggedthisdurationin
millisecondsandremovedstopwatchfromThreadLocal.
Tip
Ifyoudon’twanttoimplementallthemethodsfromtheHandlerInterceptorinterfacein
yourinterceptorclass,youmayconsiderextendingyourinterceptorfrom
org.springframework.web.servlet.handler.HandlerInterceptorAdapter.Thisisa
convenientclassprovidedbySpringMVCasadefaultimplementationofallofthe
methodsfromtheHandlerInterceptorinterface.
AftercreatingPerformanceMonitorInterceptor,weneedtoregisterourinterceptorwith
SpringMVC,whichiswhatwedidinstep5throughSpring’sspecialinterceptor
configurationelement:
<mvc:interceptors>
<bean
class="com.packt.webstore.interceptor.PerformanceMonitorInterceptor"/>
</mvc:interceptors>
Instep6,weaddedalog4j.propertiesfileinordertospecifysomeofthelogger-related
configuration.Youcanseethatweconfiguredthelogfilelocationinlog4j.propertiesas
follows:
log4j.appender.file.File=C:\\webstore\\webstore-performance.log
Finally,instep7,weranourapplicationinordertorecordsomeoftheperformance
logging,andwewereabletoseethattheloggerisworkingjustfineviatheconsole.You
canopenthelogfiletoviewtheperformancelogs.
So,weunderstoodhowtoconfigureaninterceptorandhaveseen
PerformanceMonitorInterceptorinaction.Inthenextexercise,wewilllearnhowtouse
someofSpring’spreconfiguredinterceptors.
Popquiz–interceptor
Considerthefollowinginterceptor:
publicclassSecurityInterceptorextendsHandlerInterceptorAdapter{
@Override
publicvoidafterCompletion(HttpServletRequest
request,HttpServletResponseresponse,Objecthandler,Exceptionex)throws
Exception{
//justsomecoderelatedtoaftercompletion
}
}
Q1.IsthementionedSecurityInterceptorclassavalidinterceptor?
1. ItisnotvalidbecauseitdoesnotimplementtheHandlerInterceptorinterface.
2. ItisvalidbecauseitextendstheHandlerInterceptorAdapterclass.
Q2.Whatistheorderofexecutionwithintheinterceptormethods?
1. preHandle,afterCompletion,postHandle.
2. preHandle,postHandle,afterCompletion.
Internationalization(i18n)
Internationalizationmeansadaptingcomputersoftwaretodifferentlanguagesandregional
differences.Forexample,ifyouaredevelopingawebapplicationforaDutch-based
company,theymayexpectallthewebpagetexttobedisplayedintheDutchlanguage,
usetheEuroforcurrencycalculations,expectaspaceasathousandseparatorwhen
displayingnumbers,and“,”(comma)asadecimalpoint.Ontheotherhand,whenthe
sameDutchcompanywantstoopenamarketinAmerica,theyexpectthesameweb
applicationtobeadaptedforAmericanlocales;forexample,thewebpagesshouldbe
displayedinEnglish,dollarsshouldbeusedforcurrencycalculations,numbersshouldbe
formattedwith“,”(comma)asathousandseparator,and“.”(dot)shouldbeusedasa
decimalpoint,andsoon.
Thetechniqueofdesigningawebapplicationthatcanautomaticallyadapttodifferent
regionsandcountrieswithoutneedingtobereengineerediscalledinternationalization,
sometimesshortenedtoi18N(I-eighteenletters-N).
InSpringMVC,wecanachieveinternationalizationthroughLocaleChangeInterceptor
(org.springframework.web.servlet.i18n.LocaleChangeInterceptor).The
LocaleChangeInterceptorallowsustochangethecurrentlocaleoneverywebrequest
viaaconfigurablerequestparameter.InChapter4,WorkingwithSpringTagLibraries,we
learnedhowtoexternalizetextmessagesintheaddproductspage.Now,wearegoingto
addinternationalizationsupportforthesameaddproductspage(addProducts.jsp)
becauseinSpringMVC,priortointernationalizingalabel,wemustexternalizethatlabel
first.Sincewealreadyexternalizedallthelabelmessagesintheaddproductspage
(addProducts.jsp),weshallproceedtointernationalizetheaddproductspage.
Timeforaction–adding
internationalization
Technically,wecanaddasmuchlanguagesupportaswewantforinternationalization,but
fordemonstrationpurposes,Iamgoingtoshowyouhowtomakeanaddproductpagefor
Dutchlanguagesupport.Performthefollowingsteps:
1. Createafilecalledmessages_nl.propertiesunder/src/main/resourcesinyour
project,addthefollowinglinesinit,andsavethefile:
addProduct.form.productId.label=NieuwproductID
addProduct.form.name.label=Naam
addProduct.form.unitPrice.label=Prijsunit
addProduct.form.description.label=Beschrijving
addProduct.form.manufacturer.label=Manufacturer
addProduct.form.category.label=Fabrikant
addProduct.form.unitsInStock.label=Aantalopvoorraad
addProduct.form.condition.label=ProductStaat
addProduct.form.productImage.label=Productimage
2. OpentheaddProduct.jsppageandaddthefollowingsetoftagsrightafterthe
logoutlink:
<divclass="pull-right"style="padding-right:50px">
<ahref="?language=en">English</a>|<ahref="?language=nl">Dutch</a>
</div>
3. Now,openthewebapplicationcontextconfigurationfileDispatcherServlet-
context.xmlfromsrc/main/webapp/WEB-INF/spring/webcontext/andaddone
morebeandefinitionforthelocaleresolverasfollows:
<beanid="localeResolver"
class="org.springframework.web.servlet.i18n.SessionLocaleResolver">
<propertyname="defaultLocale"value="en"/>
</bean>
4. Now,configureonemoreinterceptorinthewebapplicationcontextconfiguration;
thatmeans,addonemoreinterceptorbeanentryintheexisting<mvc:interceptors>
elementforLocaleChangeInterceptorasfollows:
<mvc:interceptors>
<beanclass=
"com.packt.webstore.interceptor.PerformanceMonitorInterceptor"/>
<beanclass=
"org.springframework.web.servlet.i18n.LocaleChangeInterceptor">
<propertyname="paramName"value="language"/>
</bean>
</mvc:interceptors>
5. Now,runtheapplicationandenter
http://localhost:8080/webstore/products/add.Youwillbeabletoseethe
regularAddproductspagewithtwoextralinksinthetop-rightcornerwhereyou
canchoosethelanguage:
Theaddproductpagedisplayinginternationalizationsupporttochooselanguages
6. Now,clickontheDutchlink.YouwillseethattheproductIDlabelhastransformed
intotheDutchcaptionNieuwproductID.
7. SincetheconfiguredLocaleChangeInterceptorwilladdarequestparametercalled
languagetothewebrequest,youneedtoaddthislanguagerequestparametertothe
whitelistingsetinyourProductControllerpage.OpentheProductController
page,andwithintheinitialiseBindermethod,addthelanguagerequestparameter
tothewhitelistingsetasfollows:
binder.setAllowedFields("productId","name","unitPrice","description","m
anufacturer","category","unitsInStock","productImage","language");
Whatjusthappened?
Instep1,wejustcreatedapropertyfilecalledmessages_nl.properties.Thisfileactsas
aDutch-basedmessagesourceforallourexternalizedlabelmessagesinthe
addProducts.jspfile.Inordertodisplaytheexternalizedlabelmessages,weusedthe
<spring:message>tagintheaddProducts.jspfile.
However,bydefault,the<spring:message>tagwillreadthemessagesfromthe
messages.propertiesfileonly,butweneedtomakeaprovisionforourenduserto
switchtotheDutchlocalewhentheyviewthewebpagesothatthelabelmessagescan
comefromthemessages_nl.propertiesfile.Weprovidedthiskindofaprovision
thoughalocalechoosinglinkinaddProducts.jsp,asmentionedinstep2.Considerthe
followingcode:
<ahref="?language=en">English</a>|<ahref="?language=nl">Dutch</a>
Instep2,wecreatedtwolinkseachtochooseeitherEnglishorDutchasthepreferred
locale.Whentheuserclicksontheselinks,itwilladdarequestparametercalledlanguage
totheURLwiththecorrespondinglocalevalue.Forexample,whenweclickonthe
Englishlinkintheaddproductspageatruntime,itwillchangetherequestURLto
http://localhost:8080/webstore/products/add?language=en.Similarly,ifweclick
ontheDutchlink,itwillchangetherequestURLto
http://localhost:8080/webstore/products/add?language=nl.
Instep3,wecreatedaSessionLocaleResolverbeaninourwebapplicationcontextas
follows:
<beanid="localeResolver"
class="org.springframework.web.servlet.i18n.SessionLocaleResolver">
<propertyname="defaultLocale"value="en"/>
</bean>
SessionLocaleResolveristheonethatsetsthelocaleattributeintheusersession.One
importantpropertyofSessionLocaleResolverisdefaultLocale.Weassignedenasthe
valuefordefaultLocale,whichindicatesthatourpageshouldusethelanguageEnglish
asthedefaultlocale.
Instep4,wecreatedaLocaleChangeInterceptorbeanandconfigureditintheexisting
interceptorlist,asfollows:
<beanclass=
"org.springframework.web.servlet.i18n.LocaleChangeInterceptor">
<propertyname="paramName"value="language"/>
</bean>
WeassignedthenamelanguageasthevalueoftheparamNamepropertyin
LocaleChangeInterceptor.Thereasonforthisisbecause,ifyounoticeinstep2,when
wecreatedthelocalechoosinglinkintheaddproductspage(addProduct.jsp),weused
thesameparameternameastherequestparameterwithinthe<a>tag:
<ahref="?language=en">English</a>|<ahref="?language=nl">Dutch</a>
Thisway,wegaveahinttoLocaleChangeInterceptortochoosethecorrectlocale
preferredbytheuser.So,whicheverparameternameyouplannedtouseinyourURL,use
thesamenameasthevaluefortheparamNamepropertyinLocaleChangeInterceptor.
And,onemorethingtokeepinmindisthatthevalueyouhavegiventothelanguage
requestparameterinthelinkshouldmatchoneofthesuffixesofthetranslationmessage
sourcefile.Forexample,inourcase,wecreatedaDutchtranslationmessagesourcefile
andnameditmessages_nl.properties.Here,thesuffixisnl.Ifmessages.properties
waswithoutanysuffix,thedefaultensuffixwillbeconsidered.That’swhy,instep2,we
gavenlandenasthevaluesofthelanguageparameterscorrespondinglyforDutchand
English:
<ahref="?language=en">English</a>|<ahref="?language=nl">Dutch</a>
Finally,whenwerunourapplicationandenter
http://localhost:8080/webstore/products/add,wewillbeabletoseeourregular
productaddpagewithextratwolinksinthetop-rightcornerforchoosingthelanguage.
ClickingontheDutchlinkwillchangetherequestURLto
http://localhost:8080/webstore/products/add?language=nl,whichwillbring
LocaleChangeInterceptortoactionandwillreadDutch-basedlabelmessagesfrom
messages_nl.properties.
Notethatifwedidn’tgiveanylanguageparameterinourURL,Springwilluseanormal
messagesourcefile(messages.properties)fortranslation.Ifwegavealanguage
parameter,Springwillusethatparametervalueasthesuffixtoidentifythecorrect
languagemessagesourcefile(messages_nl.properties).
Haveagohero–fullyinternationalizetheproduct
detailpage
Asalreadymentioned,Ihaveinternationalizedasinglewebpage(addProducts.jsp)for
demonstrationpurposes.Iencourageyoutointernationalizetheproductdetailwebpage
(product.jsp)inyourproject.YoucanusetheGoogleTranslateservice
(https://translate.google.com/)tofindtheDutchtranslationofthelabels.Alongwiththat,
trytoaddonemorelanguagesupportoptionofyourchoice.
Auditlogging
Auditloggingmeansmaintainingalogrecordtoshowwhohadaccessedacomputer
systemandwhatoperationstheyhadperformed.Inourproject,wehaveawebpageto
addproducts;wemayneedtomaintainarecordofwhoaddedwhichproductonwhich
date.Wecancreateaninterceptortomakesuchalogrecord.
Timeforaction–addingthedataaudit
interceptor
UsingasimpleMVCinterceptor,youcanaccomplishauditloggingwithoutmaking
changestoyourapplicationcode.Createaninterceptortorecordanauditlogusingthe
followingsteps:
1. CreateaclasscalledAuditingInterceptorunderthepackage
com.packt.webstore.interceptorinthesourcefoldersrc/main/javaandaddthe
followingcodeintoit:
packagecom.packt.webstore.interceptor;
importjava.text.DateFormat;
importjava.text.SimpleDateFormat;
importjava.util.Calendar;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
importorg.apache.log4j.Logger;
import
org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
publicclassAuditingInterceptorextendsHandlerInterceptorAdapter{
Loggerlogger=Logger.getLogger("auditLogger");
privateStringuser;
privateStringproductId;
publicbooleanpreHandle(HttpServletRequest
request,HttpServletResponsearg1,Objecthandler)throwsException{
if(request.getRequestURI().endsWith("products/add")
&&request.getMethod().equals("POST")){
user=request.getRemoteUser();
productId=request.getParameterValues("productId")[0];
}
returntrue;
}
publicvoid
afterCompletion(HttpServletRequestrequest,HttpServletResponseresponse,
Objecthandler,Exceptionarg3)throwsException{
if(request.getRequestURI().endsWith("products/add")
&&response.getStatus()==302){
logger.info(String.format("ANewproduct[%s]Addedby%son%s",
productId,user,getCurrentTime()));
}
}
privateStringgetCurrentTime(){
DateFormatformatter=newSimpleDateFormat("dd/MM/yyyy
'at'hh:mm:ss");
Calendarcalendar=Calendar.getInstance();
calendar.setTimeInMillis(System.currentTimeMillis());
returnformatter.format(calendar.getTime());
}
}
2. Now,configureonemoreinterceptorinthewebapplicationcontextconfigurationfile
DispatcherServlet-context.xml;thismeans,addonemoreinterceptorbeanentry
intheexisting<mvc:interceptors>tagforAuditingInterceptorasfollows:
<mvc:interceptors>
<bean
class="com.packt.webstore.interceptor.PerformanceMonitorInterceptor"/>
<beanclass=
"org.springframework.web.servlet.i18n.LocaleChangeInterceptor">
<propertyname="paramName"value="language"/>
</bean>
<beanclass="com.packt.webstore.interceptor.AuditingInterceptor"/>
</mvc:interceptors>
3. Openthepropertyfilecalledlog4j.propertiesfromthedirectory
src/main/resourcesandaddthefollowingcontentattheendofthefileandsaveit:
#AuditingLogger
log4j.logger.auditLogger=INFO,auditLogger
log4j.appender.auditLogger=org.apache.log4j.RollingFileAppender
log4j.appender.auditLogger.File=C:\\webstore\\webstore-Audit.log
log4j.appender.auditLogger.maxFileSize=1MB
log4j.appender.file.auditLogger.MaxBackupIndex=1
log4j.appender.auditLogger.layout=org.apache.log4j.PatternLayout
log4j.appender.auditLogger.layout.ConversionPattern=%d{yyyy-MM-dd
HH:mm:ss}%c:%m%n
4. Now,runtheapplicationandenter
http://localhost:8080/webstore/products/add.Youwillbeabletoseethe
regularproductaddpage;justentersomevalidvaluesandpresstheAddbutton.
5. Now,justopentheauditlogfilefromC:\\webstore\\webstore-Audit.log.Youwill
beabletoseetheauditlogs,whicharesomewhatsimilartothefollowing:
2013-12-1712:11:54auditLogger:ANewproduct[P12345]AddedbyAdmin
on17/12/2013at12:11:54
Whatjusthappened?
Instep1,wejustcreatedtheAuditingInterceptorclassbyextendingtheabstractclass
HandlerInterceptorAdapter,andweonlyoverrodetwomethods,namely,preHandle
andafterCompletion.Let’srevieweachmethodindepth,onebyone.
Asweknow,preHandlewillbecalledbeforethecontrollermethodisexecuted.Inside
preHandle,wesimplycheckwhethertheincomingrequestisofthetypePOSTand
whetherittriestomaptherequesttotheaddproductpageproducts/add.Ifitdoes,the
remoteusernameandnewlyaddedproductIDwerestoredinthecorrespondingmember
variablesoftheAuditingInterceptorclass:
publicbooleanpreHandle(HttpServletRequestrequest,HttpServletResponse
arg1,Objecthandler)throwsException{
if(request.getRequestURI().endsWith("products/add")&&
request.getMethod().equals("POST")){
user=request.getRemoteUser();
productId=request.getParameterValues("productId")[0];
}
returntrue;
}
IntheafterCompletionmethod,wearesimplyloggingtheusernameandnewlyadded
productIDaftercheckingwhethertheresponsestatusisofthetyperedirecting(the
HTTPresponsestatus302):
publicvoidafterCompletion(HttpServletRequestrequest,HttpServletResponse
response,Objecthandler,Exceptionarg3)throwsException{
if(request.getRequestURI().endsWith("products/add")
&&response.getStatus()==302){
logger.info(String.format("ANewproduct[%s]Addedby%son%s",
productId,user,getCurrentTime()));
}
}
Instep2,weregisteredAuditingInterceptorwithSpringMVCthroughSpring’sspecial
interceptorconfigurationtag.Wewanttorecordourrelateddataauditinglogsina
separatefile.That’swhy,instep3,weaddedaconfigurationrelatedtodataauditinginthe
log4j.propertiesfile.Youcanseethatwehaveconfiguredthedataauditinglogfile
locationinlog4j.propertiesasfollows:
log4j.appender.auditLogger.File=C:\\webstore\\webstore-Audit.log
Finally,whenwerunourapplicationandaddsomenewproducts,wewillbeabletosee
therecordeddataauditlogentryinthewebstore-Audit.logfile.
Conditionalredirecting
Sofar,wehaveseenmanyapplicationsoftheinterceptorinSpringMVC,suchas
performancelogging,internationalization,andauditlogging.However,usinginterceptor,
notonlycanweinterceptthewebrequest,butevenbypassorredirecttheoriginalweb
request.
Timeforaction–interceptingofferpage
requests
Forexample,considerasituationwhereyouwanttoshowthespecialofferproductspage
toonlythoseuserswhohaveavalidpromocode.Theotherstryingtoaccessthespecial
offerproductspagewithaninvalidpromocodeshouldberedirectedtoanerrorpage.
Achievethispieceoffunctionalitywiththehelpoftheinterceptorbyperformingthe
followingsteps:
1. CreateaclassnamedPromoCodeInterceptorunderthe
com.packt.webstore.interceptorpackageinthesourcefoldersrc/main/javaand
addthefollowingcodeintoit:
packagecom.packt.webstore.interceptor;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
import
org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
publicclassPromoCodeInterceptorextendsHandlerInterceptorAdapter{
privateStringpromoCode;
privateStringerrorRedirect;
privateStringofferRedirect;
publicbooleanpreHandle(HttpServletRequest
request,HttpServletResponseresponse,Objecthandler)throwsException{
StringgivenPromoCode=request.getParameterValues("promo")==null
?"":request.getParameterValues("promo")[0];
if(request.getRequestURI().endsWith("products/specialOffer")){
if(givenPromoCode.equals(promoCode)){

response.sendRedirect(request.getContextPath()+"/"+offerRedirect);
}else{
response.sendRedirect(errorRedirect);
}
returnfalse;
}
returntrue;
}
publicStringgetPromoCode(){
returnpromoCode;
}
publicvoidsetPromoCode(StringpromoCode){
this.promoCode=promoCode;
}
publicStringgetErrorRedirect(){
returnerrorRedirect;
}
publicvoidsetErrorRedirect(StringerrorRedirect){
this.errorRedirect=errorRedirect;
}
publicStringgetOfferRedirect(){
returnofferRedirect;
}
publicvoidsetOfferRedirect(StringofferRedirect){
this.offerRedirect=offerRedirect;
}
}
2. Now,configureonemoreinterceptorinthewebapplicationcontext
DispatcherServlet-context.xml;thatmeans,addonemoreinterceptorbeanentry
intheexisting<mvc:interceptors>tagforPromoCodeInterceptor,asfollows:
<mvc:interceptors>
<beanclass=
"com.packt.webstore.interceptor.PerformanceMonitorInterceptor"/>
<bean
class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor">
<propertyname="paramName"value="language"/>
</bean>
<beanclass="com.packt.webstore.interceptor.AuditingInterceptor"/>
<beanclass="com.packt.webstore.interceptor.PromoCodeInterceptor">
<propertyname="promoCode"value="OFF3R"/>
<propertyname="errorRedirect"value="invalidPromoCode"/>
<propertyname="offerRedirect"value="products"/>
</bean>
</mvc:interceptors>
3. OpentheProductControllerclass,andaddonemorerequestmappingmethodtoit
asfollows:
@RequestMapping("/invalidPromoCode")
publicStringinvalidPromoCode(){
return"invalidPromoCode";
}
4. Finally,addonemoreJSPviewfilecalledinvalidPromoCode.jspunderthe
directorysrc/main/webapp/WEB-INF/views/,andaddthefollowingcodesnippet
intoitandsaveit:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
<html>
<head>
<metahttp-equiv="Content-Type"content="text/html;charset=ISO-
8859-1">
<link
rel="stylesheet"href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/boo
tstrap.min.css">
<title>Invalidpromocode</title>
</head>
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1class="alertalert-danger">Invalidpromocode</h1>
</div>
</div>
</section>
<section>
<divclass="container">
<p>
<ahref="<spring:urlvalue="/products"/>"class="btnbtn-
primary">
<spanclass="glyphicon-hand-leftglyphicon"></span>
products
</a>
</p>
</div>
</section>
</body>
</html>
5. Now,runtheapplicationandenter
http://localhost:8080/webstore/products/specialOffer?promo=offer.You
willseeapagedisplayinganerrormessageasfollows:
6. Now,enterhttp://localhost:8080/webstore/products/specialOffer?
promo=OFF3R.Youwillberedirectedtoaspecialofferproductpage.
Whatjusthappened?
ThePromoCodeInterceptorclasswecreatedinstep1issimilarto
AuditingInterceptor;theonlydifferenceisthatweoverrodeonlythepreHandle
method.InthepreHandlemethod,wesimplycheckedwhethertheincomingrequestwas
tryingtoaccessthespecialofferproductpage(products/specialOffer):
publicbooleanpreHandle(HttpServletRequestrequest,HttpServletResponse
response,Objecthandler)throwsException{
StringgivenPromoCode=request.getParameterValues("promo")==null
?"":request.getParameterValues("promo")[0];
if(request.getRequestURI().endsWith("products/specialOffer")){
if(givenPromoCode.equals(promoCode)){
response.sendRedirect(request.getContextPath()+"/"+offerRedirect);
}else{
response.sendRedirect(errorRedirect);
}
returnfalse;
}
returntrue;
}
WecheckagainwhethertherequestcontainsthecorrectpromocodeastheHTTP
parameterandredirecttherequesttotheconfiguredspecialofferpage;otherwise,we
redirectittotheconfigurederrorpage.
Okay,wecreatedthePromoCodeInterceptorclass,butwehavetoconfigurethis
interceptorwithourSpringMVCruntime,whichiswhatwedidinstep2,byaddingthe
followingbeandefinitionwithintheSpringMVCspecialinterceptorconfigurationtag:
<beanclass="com.packt.webstore.interceptor.PromoCodeInterceptor">
<propertyname="promoCode"value="OFF3R"/>
<propertyname="errorRedirect"value="invalidPromoCode"/>
<propertyname="offerRedirect"value="products"/>
</bean>
ThePromoCodeInterceptorclasshasthreeproperties,namely,promoCode,
errorRedirect,andofferRedirect.ThepromoCodepropertyisusedtoconfigurethe
validpromocode;inourcase,weassignedOFF3Rasthevalidpromocode,sowhoeveris
accessingthespecialofferpageshouldprovideOFF3RasthepromocodeintheirHTTP
parameterinordertoaccessthepage.
Thenexttwoattributes,errorRedirectandofferRedirect,areusedinredirection.The
errorRedirectpropertyindicatestheredirectURLmappinginthecaseofaninvalid
promocode,andtheofferRedirectpropertyindicatestheredirectURLmappingfor
successfulpromocoderedirection.
Tip
NotethatIdidnotcreateanyspecialofferproductpage.Justfordemonstrationpurposes,
Ireusedthesameregularproductspageasthespecialofferproductspage;that’swhy,I
assignedproductsasthevaluefortheofferRedirectattribute,sointhecaseofavalid
promocode,Iwillberedirectedtotheregularproducts/page.However,ifIcreatedany
specialofferproductJSPpage,Icanassignthatpage’sURLasthevaluefor
offerRedirect.
Instep3,weaddedonemorerequestmappingmethodcalledinvalidPromoCodetoshow
anerrorpageinthecaseofaninvalidpromocode.Andinstep4,weaddedthe
correspondingerrorviewfilecalledinvalidPromoCode.jsp.
Finally,instep5,wepurposelyentered
http://localhost:8080/webstore/products/specialOffer?promo=offerinour
runningapplicationtodemonstratethePromoCodeInterceptoraction;additionally,we
sawtheerrorpagebecausethepromocodeweprovidedintheURLisoffer(?
promo=offer),whichisincorrect.Instep6,weprovidedthecorrectpromocodeinthe
URLhttp://localhost:8080/webstore/products/specialOffer?promo=OFF3Rsothat
weareabletoseetheconfiguredspecialofferproductspage.
Summary
Inthischapter,weunderstoodtheconceptoftheinterceptorandlearnedhowtoconfigure
theinterceptorinSpringMVC.Welearnedhowtodoperformanceloggingusingthe
interceptor.WealsolearnedhowtouseSpring’sLocaleChangeInterceptortosupport
internationalization.Later,welearnedhowtodoauditloggingusingtheinterceptor.
Finally,welearnedhowtodoconditionalredirectingusingtheinterceptor.
Inthenextchapter,Iwillintroduceyoutovalidation.Youwilllearnhowtodoform
validationandothertypesofcustomvalidations.
Chapter7.ValidateYourProductswitha
Validator
Themostcommonexpectedbehaviorofanywebapplicationisthatitshouldvalidateuser
data.Everytimeausersubmitsdataintoourwebapplication,itneedstobevalidated.
Thisistopreventsecurityattacks,wrongdata,orsimpleusermistakeerrors.Wedon’t
havecontroloverwhatusersmaytypewhensubmittingdataintoourwebapplication.
Forexample,theymaytypesometextinsteadofadate,theymayforgettofillmandatory
fields,orsupposeweusedalengthof12charactersforafieldinthedatabaseandthe
userentereddatathelengthof15characters,thenthedatacannotbesavedinthe
database.Similarly,therearelotsofwaysthatausercanfeedincorrectdataintoourweb
application.Ifweacceptthesevaluesasvalid,thenitwillcreateerrorsandbugswhenwe
processsuchinputs.Thischapterwillexplainthebasicsofsettingupvalidationwith
SpringMVC.
Afterfinishingthischapter,youwillhaveaclearideaaboutthefollowing:
JSR-303beanvalidation
Customvalidation
Springvalidation
Beanvalidation
Javabeanvalidation(JSR-303)isaJavaspecificationthatallowsustoexpressvalidation
constraintsonobjectsviaannotations.ItprovidestheAPIstovalidateandreport
violations.Thehibernatevalidatoristhereferenceimplementationofthebeanvalidation
specification.Wearegoingusethehibernatevalidatorforvalidation.Youcanseethe
availablebeanvalidationannotationatthefollowingURL:
http://docs.oracle.com/javaee/6/tutorial/doc/gircz.html
Timeforaction–addingbeanvalidation
support
Inthissection,youwilllearnhowtovalidateaformsubmissioninaSpringMVC
application.Inourproject,wehavetheaddproductsformalready.Addsomevalidationto
thisformbyperformingthefollowingsteps:
1. Openthepom.xmlfile—youcanfindpom.xmlundertherootdirectoryoftheproject
itself.
2. Youwillseesometabsatthebottomofthepom.xmlfile.SelecttheDependencies
tabandclickontheAddbuttonintheDependenciessection.
3. ASelectDependencywindowwillappear;enterGroupIdasorg.hibernate,enter
ArtifactIdashibernate-validator,enterVersionas4.3.1.Final,selectScopeas
compile,andclickontheOKbuttonandsavepom.xml.
4. OpentheProductdomainclassandaddthe@Patternannotation
(javax.validation.constraints.Pattern)atthetopoftheproductIdfieldas
follows:
@Pattern(regexp="P[0-9]+",message="
{Pattern.Product.productId.validation}")
privateStringproductId;
5. Similarly,addthe@Size,@Min,@Digits,and@NotNullannotations
(javax.validation.constraints.*)atthetopofthenameandunitPricefields,
respectively,asfollows:
@Size(min=4,max=50,message="{Size.Product.name.validation}")
privateStringname;
@Min(value=0,message="Min.Product.unitPrice.validation}")
@Digits(integer=8,fraction=2,message="
{Digits.Product.unitPrice.validation}")
@NotNull(message="{NotNull.Product.unitPrice.validation}")
privateBigDecimalunitPrice;
6. Openthemessagesourcefilemessages.propertiesfrom/src/main/resourcesin
yourprojectandaddthefollowingentriesinit:
Pattern.Product.productId.validation=InvalidproductID.Itshould
startwithcharacterPfollowedbynumber.
Size.Product.name.validation=Invalidproductname.Itshouldbe
minimum4characterstomaximum50characterslong.
Min.Product.unitPrice.validation=UnitpriceisInvalid.Itcannot
havenegativevalues.
Digits.Product.unitPrice.validation=UnitpriceisInvalid.Itcanhave
maximumof2digitfractionand8digitinteger.
NotNull.Product.unitPrice.validation=UnitpriceisInvalid.Itcannot
beempty.
7. OpentheProductControllerclassandchangetheprocessAddNewProductForm
requestmappingmethodbyaddingan@Validannotation
(javax.validation.Valid)infrontoftheproductToBeAddedparameter.Afteryou
aredonewiththis,yourprocessAddNewProductFormmethodsignatureshouldlook
asfollows:
publicStringprocessAddNewProductForm(@ModelAttribute("newProduct")
@ValidProductproductToBeAdded,BindingResultresult,
HttpServletRequestrequest){
8. Now,withinthebodyoftheprocessAddNewProductFormmethod,addthefollowing
conditionasthefirststatement:
if(result.hasErrors()){
return"addProduct";
}
9. OpentheaddProduct.jsppagefromsrc/main/webapp/WEB-INF/views/inyour
projectandaddthe<form:errors>tagfortheproductId,name,andunitPriceinput
elements.Forexample,theproductIDinputtagwillhavethe<form:errors>tag
besideit,asfollows:
<form:inputid="productId"path="productId"type="text"
class="form:input-large"/>
<form:errorspath="productId"cssClass="text-danger"/>
Rememberthatthepathattributevalueshouldalwaysbethesameasthe
correspondinginputtag.
10. Now,addaglobal<form:errors>tagwithinthe<form:form>tagasfollows:
<form:errorspath="*"cssClass="alertalert-danger"element="div"/>
11. AddthebeanconfigurationforLocalValidatorFactoryBeaninyourwebapplication
contextconfigurationfileDispatcherServlet-context.xmlasfollows:
<beanid="validator"
class="org.springframework.validation.beanvalidation.LocalValidatorFact
oryBean">
<propertyname="validationMessageSource"ref="messageSource"/>
</bean>
12. Finally,assignthevalidatorpropertyvaluetothe<mvc:annotation-driven>tagas
follows:
<mvc:annotation-drivenenable-matrix-variables="true"
validator="validator"/>
13. Now,runtheapplicationandenter
http://localhost:8080/webstore/products/add.Youwillseeawebpage
displayingawebformtoaddtheproductinformation;withoutfillinganyvalueinthe
form,simplyclickontheAddbutton.Youwillseevalidationmessagesatthetopof
theformasfollows:
TheAddnewproductwebformdisplayingthevalidationmessage
Whatjusthappened?
Sincewedecidedtousethebeanvalidation(JSR-303)specification,weneedan
implementationofthebeanvalidationspecification.Wedecidedtousethehibernate
validatorimplementationinourproject,soweneedtoaddthatJARfiletoourprojectasa
dependency.That’swhatwedidinsteps1to3.
Insteps4and5,weaddedsomejavax.validation.constraintsannotations,suchas
@Pattern,@Size,@Min,@Digits,and@NotNulltoourdomainclassfields
(Product.java).Usingtheseannotations,wecandefinevalidationconstraintsonfields.
Therearemorevalidationconstraintannotationsavailableunderthe
javax.validation.constraintspackage.Justfordemonstrationpurposes,Iuseda
coupleofannotations;youcancheckoutthebeanvalidationdocumentationforallthe
availablelistsofconstraints.
Forexample,takethe@PatternannotationabovetheproductIdfield;itwillcheck
whetherthegivenvalueofthefieldmatchestheregularexpressionspecifiedintheregexp
attributeofthe@Patternannotation.Inourexample,wejustenforcethatthevaluegiven
fortheproductIdfieldshouldstartwiththecharacterPandbefollowedbydigits,as
follows:
@Pattern(regexp="P[0-9]+",message="
{Pattern.Product.productId.validation}")
privateStringproductId;
Themessageattributeofeveryvalidationannotationjustactsasakeytotheactual
messagefromthemessagesourcefile(messages.properties).Inourcase,wespecified
Pattern.Product.productId.validationasthekey,soweneedtodefinetheactual
validationmessageinthemessagesourcefile.That’swhy,weaddedsomemessageentries
instep6.Ifyounoticedthecorrespondingvalueforthekey
Pattern.Product.productId.validationinthemessages.propertiesfile,youwill
noticethefollowingvalue:
Pattern.Product.productId.validation=InvalidproductID.Itshouldstart
withcharacterPfollowedbynumber.
Tip
Notethatyoucanevenaddlocalizederrormessagesinthecorrespondingmessagesource
fileifyouwant.Forexample,ifyouwanttoshowerrormessagesinDutch,simplyadd
errormessageentriesinthemessages_nl.propertiesfileaswell.Duringvalidation,this
messagesourcewillbepickedupautomaticallybySpringbasedonthechosenlocale.
Wedefinedthevalidationconstraintsinourdomainobjectandalsodefinedthevalidation
errormessagesinourmessagesourcefile;whatelsedoweneedtodo?Weneedtotellour
controllertovalidatetheformsubmissionrequest.Wedidthisinsteps7and8inthe
processAddNewProductFormmethod.Considerthefollowingcodesnippet:
@RequestMapping(value="/add",method=RequestMethod.POST)
publicStringprocessAddNewProductForm(@Valid@ModelAttribute("newProduct")
ProductproductToBeAdded,BindingResultresult){
if(result.hasErrors()){
return"addProduct";
}
if(result.getSuppressedFields().length>0){
thrownewIllegalAccessError("Attemptingtobinddisallowedfields");
}
productService.addProduct(productToBeAdded);
return"redirect:/products";
}
WefirstannotatedourmethodparameterproductToBeAddedwiththe@Validannotation
(javax.validation.Valid).Bydoingso,wedirectedSpringMVCtousethebean
validationframeworktovalidatetheproductToBeAddedobject—asyoualreadyknow,the
productToBeAddedobjectisourform-backedbean.Aftervalidatingtheincomingform
bean(productToBeAdded),Springwillstoretheresultsintheresultobject,whichagain
isanothermethodparameteroftheprocessAddNewProductFormmethod.
Instep8,wesimplycheckedwhethertheresultobjectcontainsanyerrors;ifitdoes,we
redirecttothesameaddproductpage.Otherwise,weproceedtoaddproductToBeAddedto
ourrepository.
Sofar,everythingisfine.First,wedefinedtheconstraintsonourdomainobjectandthe
errormessagesinthemessagesourcefile(messages.properties).Later,wevalidated
andcheckedthevalidationresultinthecontrollerformprocessingmethod
(processAddNewProductForm).However,wehaven’tmentionedhowtodisplaytheerror
messagesintheviewfile.WeuseSpring’sspecial<form:errors>tagforthispurpose.
WeaddedthistagfortheproductId,name,andunitPriceinputelementsinstep9.Ifany
oftheinputfieldsfailedduringvalidation,thecorrespondingerrormessagewillbepicked
upbythis<form:errors>tag:
<form:errorspath="productId"cssClass="text-danger"/>
Thepathattributeisusedtoidentifythefieldintheformbeantolookforerrors,andthe
cssClassattributeisusedtostyletheerrormessage.IhaveusedBootstrap’sstyleclass,
text-danger,butyoucanuseanyvalidCSSstyleclassthatyouprefertoapplyonthe
errormessage.
Similarly,instep10,weaddedaglobal<form:errors>tagtoshowallerrormessagesas
aconsolidatedviewatthetopoftheform,asfollows:
<form:errorspath="*"cssClass="alertalert-danger"element="div"/>
Here,weusedthe*symbolforthepathattribute;thismeansthatwewanttoshowallof
theerrors.AndelementattributesindicatewhichtypeofelementSpringshouldusetolist
alloftheerrors.
Sofar,wehaveperformedallofthecoding-relatedexercisesneededtoenablevalidation,
butwehavetodoonefinalconfigurationinourwebapplicationcontexttoenable
validation;thatis,weneedtointroducethebeanvalidationframeworktoSpringMVC.In
steps11and12,wedidjustthat;wecreatedabeanconfigurationfor
LocalValidatorFactoryBean
(org.springframework.validation.beanvalidation.LocalValidatorFactoryBean):
<beanid="validator"
class="org.springframework.validation.beanvalidation.LocalValidatorFactoryB
ean">
<propertyname="validationMessageSource"ref="messageSource"/>
</bean>
ThisLocalValidatorFactoryBeanwillinitiatethehibernatevalidatorwhenour
applicationisbeingbooted.ThevalidationMessageSourcepropertyof
LocalValidatorFactoryBeanindicateswhichmessagesourcebeanshouldlookforerror
messages.Sincewealreadyconfiguredamessagesourcebeaninourwebapplication
contextaspartofChapter6,InterceptYourStorewithInterceptor,canmakeuseofthat
messageSourcebeanasthevalueforthevalidationMessageSourceproperty.Wewill
alreadybeabletoseeabeandefinitionwiththenamemessageSourceinourweb
applicationcontext.
Finally,weintroducedourvalidatorbeantoSpringMVCthroughthe
<mvc:annotation-driven>tagbyaddingoneextrapropertycalledvalidator,as
follows:
<mvc:annotation-drivenenable-matrix-variables="true"
validator="validator"/>
Thatisallwedidtoenablevalidation;nowifwerunourapplicationandgettheadd
productpageusingtheURLhttp://localhost:8080/webstore/products/add,wewill
seetheemptyformreadytobesubmitted.Ifwesubmitthisformwithoutfillingany
information,weseeerrormessagesinred.
Haveagohero–addingmorevalidationintheadd
productspage
Ijustaddedvalidationforthefirstthreefieldsintheproductdomainclass;youcanextend
thevalidationfortheremainingfields.Trytoaddlocalizederrormessagesforthe
validationthatyouaredefining.
Thefollowingaresomehintsthatyoucantryout:
Addavalidationtoshowavalidationmessageifthecategoryfiledisempty
TrytoaddavalidationtotheunitsInStockfieldtovalidatethattheminimum
allowednumberofunitsinstockiszero
CustomvalidationwithJSR-303/bean
validation
InthepreviousTimeforactionsection,welearnedhowtousestandardJSR-303bean
validationannotationstovalidatethefieldsofourdomainobject.Thisworksgreatfor
simplevalidations,butsometimes,weneedtovalidatesomecustomrulesthataren’t
availableinstandardannotations.Forexample,whatifweneedtovalidatethatthenewly
addedproductIDisnotthesameasanyoftheexistingproductIDs?Toaccomplishsuch
kindsofvalidations,wecanusecustomvalidationannotations.
Timeforaction–addingcustom
validationsupport
Inthissection,youwilllearnhowtocreatecustomvalidationannotationsandusethem.
AddacustomproductIDvalidationtoyouraddproductpagetovalidateduplicateproduct
IDsbyperformingthefollowingsteps:
1. CreateanannotationinterfacecalledProductId(ProductId.java)underthe
packagecom.packt.webstore.validatorinthesourcefoldersrc/main/java.Then,
addthefollowingcodesnippetinit:
packagecom.packt.webstore.validator;
importstaticjava.lang.annotation.ElementType.ANNOTATION_TYPE;
importstaticjava.lang.annotation.ElementType.FIELD;
importstaticjava.lang.annotation.ElementType.METHOD;
importstaticjava.lang.annotation.RetentionPolicy.RUNTIME;
importjava.lang.annotation.Documented;
importjava.lang.annotation.Retention;
importjava.lang.annotation.Target;
importjavax.validation.Constraint;
importjavax.validation.Payload;
@Target({METHOD,FIELD,ANNOTATION_TYPE})
@Retention(RUNTIME)
@Constraint(validatedBy=ProductIdValidator.class)
@Documented
public@interfaceProductId{
Stringmessage()default"
{com.packt.webstore.validator.ProductId.message}";
Class<?>[]groups()default{};
publicabstractClass<?extendsPayload>[]payload()default{};
}
2. Now,createaclasscalledProductIdValidatorunderthepackage
com.packt.webstore.validatorinthesourcefoldersrc/main/java.Then,addthe
followingcodeintoit:
packagecom.packt.webstore.validator;
importjavax.validation.ConstraintValidator;
importjavax.validation.ConstraintValidatorContext;
importorg.springframework.beans.factory.annotation.Autowired;
importcom.packt.webstore.domain.Product;
importcom.packt.webstore.service.ProductService;
publicclassProductIdValidatorimplements
ConstraintValidator<ProductId,String>{
@Autowired
privateProductServiceproductService;
publicvoidinitialize(ProductIdconstraintAnnotation){
//intentionallyleftblank;thisistheplacetoinitializethe
constraintannotationforanysensibledefaultvalues.
}
publicbooleanisValid(Stringvalue,ConstraintValidatorContext
context){
Productproduct;
try{
product=productService.getProductById(value);
}catch(ProductNotFoundExceptione){
returntrue;
}
if(product!=null){
returnfalse;
}
returntrue;
}
}
3. Openthemessagesourcefilemessages.propertiesfrom/src/main/resourcesin
yourprojectandaddthefollowingentryinit:
com.packt.webstore.validator.ProductId.message=Aproductalready
existswiththisproductid.
4. Finally,opentheProductdomainclass(Product.java)andannotatetheproductId
fieldwiththenewlycreatedProductIdannotationasfollows:
@Pattern(regexp="P[0-9]+",message="
{Pattern.Product.productId.validation}")
@ProductId
privateStringproductId;
5. Now,runtheapplicationandenter
http://localhost:8080/webstore/products/add.Youwillseeawebpage
displayingawebformtoaddtheproductinformation.Fillthecompletevalueinthe
form;particularly,filltheproductIDfieldwiththevalueP1234andsimplyclickon
theAddbutton.Youwillseevalidationmessagesatthetopoftheform,asfollows:
TheAddnewproductwebformdisplayingcustomvalidation
Whatjusthappened?
Instep1,wejustcreatedourcustomvalidationannotationcalledProductId.Every
customvalidationannotationwecreateshouldneedtobeannotatedwiththe@Constraint
annotation(javax.validation.Constraint).The@Constraintannotationhasan
importantpropertycalledvalidatedBy,whichindicatestheclassthatisperformingthe
actualvalidation.Inourcase,wegaveavalueProductIdValidator.classforthe
validatedByproperty.So,ourProductIdvalidationannotationwillexpectaclasscalled
ProductIdValidator.That’swhy,instep2,wecreatedtheProductIdValidatorclassby
implementingtheConstraintValidatorinterface
(javax.validation.ConstraintValidator).
WeannotatedtheProductIdValidatorclasswiththe@Componentannotation
(org.springframework.stereotype.Component);the@Componentannotationisanother
stereotypeannotationthatisavailableinSpring.Itissimilartothe@Repositoryor
@Serviceannotation.Whenourapplicationisbeingbooted,Springcreatesandmaintains
anobjectfortheProductIdValidatorclass.So,ProductIdValidatorbecomesa
managedbeaninourwebapplicationcontext,whichisthereasonweareabletoautowire
theproductServicebeaninProductIdValidator.
Next,weautowiredtheProductServiceobjectintheProductIdValidatorclass;whydid
wedothis?ItisbecauseinsidetheisValidmethodoftheProductIdValidatorclass,we
usedproductServicetocheckwhetheranyproductexiststhathasthegivenID.Consider
thefollowingcodesnippet:
publicbooleanisValid(Stringvalue,ConstraintValidatorContextcontext){
Productproduct;
try{
product=productService.getProductById(value);
}catch(ProductNotFoundExceptione){
returntrue;
}
if(product!=null){
returnfalse;
}
returntrue;
}
IfanyproductexiststhathasthegivenproductID,weinvalidatethevalidationby
returningfalse;otherwise,wepassthevalidationbyreturningtrue.
Instep3,wejustaddedourdefaulterrormessageforourcustomvalidationannotationin
themessagesourcefile(messages.properties).Ifyouobservedcarefully,thekey
(com.packt.webstore.validator.ProductId.message)weusedinourmessagesource
fileisthesameasthedefaultkeythatwedefinedintheProductId(ProductId.java)
validationannotation:
Stringmessage()default"
{com.packt.webstore.validator.ProductId.message}";
Finally,instep4,weusedthenewlycreatedProductIdvalidationannotationinour
domainclass(Product.java).ItactsinawaysimilartoanyotherJSR-303validation
annotation.
Thus,youwillbeabletoseetheerrormessageonthescreenwhenyouentertheexisting
productIDastheproductIDforthenewlyaddedproduct.
Haveagohero–addingcustomvalidationtoa
category
Createacustomvalidationannotationcalled@Categorythatwillallowonlysomeofthe
predefinedconfiguredcategoriestobeentered.Considerthefollowingthingswhile
implementingyourcustomannotation:
CreateanannotationinterfacecalledCategoryValidatorunderthe
com.packt.webstore.validatorpackage
CreateacorrespondingconstraintvalidatorcalledCategoryValidatorunderthe
packagecom.packt.webstore.validator
Addthecorrespondingerrormessageinthemessagesourcefile
YourCategoryValidatorinterfaceshouldmaintainalistofallowedcategories
(List<String>allowedCategories)tocheckwhetherthegivencategoryexists
underthelistofallowedcategories
Don’tforgettoinitializetheallowedCategorieslistintheconstructorofthe
CategoryValidatorclass
AnnotatethecategoryfieldoftheProductdomainclasswiththe@Category
annotation
Afterapplyingyourcustomvalidationannotation,@category,onthecategoryfieldofthe
Productdomainclass,youraddproductpageshouldrejecttheproductsofother
categoriesthathavenotbeenconfiguredinCategoryValidator.
Springvalidation
WehaveseenhowtoincorporatetheJSR-303beanvalidationwithSpringMVC.In
additiontobeanvalidation,Springhasitsownclassicmechanismtoperformvalidationas
wellwhatiscalledSpringvalidation.TheJSR-303beanvalidationismuchmoreelegant,
expressive,and,ingeneral,simplertousecomparedtotheclassicSpringvalidation.
However,theclassicSpringvalidationisveryflexibleandextensible.Forexample,
consideracross-fieldvalidationwherewewanttocomparetwoormorefieldstoseeif
theirvaluescanbeconsideredasvalidwhencombined.Insuchacase,wecanuseSpring
validation.
Inthelastsection,whereweelaboratedontheuseoftheJSR-303beanvalidation,we
validatedsomeoftheindividualfieldsonourproductdomainobject;wehaven’tdoneany
validationthatcombinestwoormorefields.Wedon’tknowwhetherthecombinationof
differentfieldsmakessense.
Timeforaction–addingSpring
validation
Ifyouhaveaconstraintthatdoesn’tallowanyonetoaddmorethan99unitsofany
productiftheunitpriceisgreaterthan1000USDforthatproduct,addsuchavalidation
usingSpringvalidationintheproject.Performthefollowingsteps:
1. CreateaclasscalledUnitsInStockValidatorunderthe
com.packt.webstore.validatorpackageinthesourcefoldersrc/main/java.Add
thefollowingcodeintoit:
packagecom.packt.webstore.validator;
importjava.math.BigDecimal;
importorg.springframework.stereotype.Component;
importorg.springframework.validation.Errors;
importorg.springframework.validation.Validator;
importcom.packt.webstore.domain.Product;
@Component
publicclassUnitsInStockValidatorimplementsValidator{
publicbooleansupports(Class<?>clazz){
returnProduct.class.isAssignableFrom(clazz);
}
publicvoidvalidate(Objecttarget,Errorserrors){
Productproduct=(Product)target;
if(product.getUnitPrice()!=null&&
newBigDecimal(10000).compareTo(product.getUnitPrice())<=0
&&product.getUnitsInStock()>99){

errors.rejectValue("unitsInStock","com.packt.webstore.validator.UnitsIn
StockValidator.message");
}
}
}
2. Openthemessagesourcefilemessages.propertiesfrom/src/main/resourcesin
theprojectandaddthefollowingentryinit:
com.packt.webstore.validator.UnitsInStockValidator.message=Youcannot
addmorethan99unitsiftheunitpriceisgreaterthan10000.
3. OpentheProductControllerclassandautowireareferencetothe
UnitsInStockValidatorclassasfollows:
@Autowired
privateUnitsInStockValidatorunitsInStockValidator;
4. Now,insidetheinitialiseBindermethodintheProductControllerclass,addthe
followingline:
binder.setValidator(unitsInStockValidator);
5. Now,runtheapplicationandenter
http://localhost:8080/webstore/products/add.Youwillbeabletoseeaweb
pageshowingawebformtoaddproductinformation.Fillallthevaluesintheform;
inparticular,filltheUnitPricefieldwiththevalue10000andtheUnitsInStock
fieldwiththevalue100;nowsimplyclickontheAddbutton.Youwillseevalidation
messagesonthetopoftheform,shownasfollows:
TheAddnewproductwebformdisplayingcross-fieldvalidation
Whatjusthappened?
InclassicSpringvalidation,themainvalidationconstructistheValidatorinterface
(org.springframework.validation.Validator).TheSpringValidatorinterfacedefines
twomethodsforvalidationpurposes,namely,supportsandvalidate.Thesupports
methodindicateswhetherthevalidatorcanvalidateaspecificclass.Ifitcan,thevalidate
methodcanbecalledtovalidateanobjectofthatclass.
EverySpring-basedvalidatorwecreateshouldimplementthisinterface.Instep1,wedid
justthat;wesimplycreatedaclasscalledUnitsInStockValidator,whichimplementsthe
SpringValidatorinterface.
InsidethevalidatemethodoftheUnitsInStockValidatorclass,wesimplycheck
whetherthegivenProductobjecthasaunitpricegreaterthan1000andthenumberof
unitsinstockismorethan99;ifitdoes,werejectthatvaluewithacorrespondingerror
keytoshowtheerrormessagefromthemessagesourcefile,shownasfollows:
@Override
publicvoidvalidate(Objecttarget,Errorserrors){
Productproduct=(Product)target;
if(product.getUnitPrice()!=null&&
newBigDecimal(10000).compareTo(product.getUnitPrice())<=0
&&product.getUnitsInStock()>99){

errors.rejectValue("unitsInStock","com.packt.webstore.validator.UnitsInStoc
kValidator.message");
}
}
Instep2,wesimplyaddedtheactualerrormessagefortheerrorkey
com.packt.webstore.validator.UnitsInStockValidator.messageinthemessage
sourcefile(messages.properties).
Wecreatedthevalidator,buttokickinthevalidation,weneedtoassociatethatvalidator
withthecontroller.That’swhatwedidinsteps3and4.Instep3,wesimplyaddedand
autowiredthereferencetoUnitsInStockValidatorintheProductControllerclass.We
alsoassociatedunitsInStockValidatorwithWebDataBinderintheinitialiseBinder
methodasfollows:
@InitBinder
publicvoidinitialiseBinder(WebDataBinderbinder){

binder.setAllowedFields("productId","name","unitPrice","description","manuf
acturer","category","unitsInStock","productImage");
binder.setValidator(unitsInStockValidator);
}
That’sit!WecreatedandconfiguredourSpring-basedvalidatortodothevalidation.Now,
werunourapplicationandenterhttp://localhost:8080/webstore/products/addto
showthewebformusedforaddingtheproductinformation.Fillthevalueintheform;in
particular,filltheUnitPricefieldwiththevalue10000andtheUnitsInStockfieldwith
thevalue100.Then,clickontheAddbutton.Youwillseevalidationmessagesatthetop
oftheformstatingYoucannotaddmorethan99unitsiftheunitpriceisgreaterthan
10000.
ItisgoodthatwehaveaddedSpring-basedvalidationintoourapplication.However,since
weconfiguredourSpring-basedvalidator(unitsInStockValidator)with
WebDataBinder,thebeanvalidationthatweconfiguredearlierwillnottakeeffect.Spring
MVCsimplyignorestheseJSR-303beanvalidationannotations(@Pattern,@Size,@Min,
@Digits,@NotNull,andsoon).
Timeforaction–combiningSpringand
beanvalidations
YouneedtowritethepreviousbeanvalidationsagaininaclassicSpring-basedvalidation,
whichisnotagoodidea,butthankstotheflexibilityandextensibilityofSpring
validation,youcancombinebothaSpring-basedvalidationandbeanvalidationtogether
withalittleextracode.Performthefollowingsteps:
1. CreateaclasscalledProductValidatorunderthecom.packt.webstore.validator
packageinthesourcefoldersrc/main/java.Then,addthefollowingcodeintoit:
packagecom.packt.webstore.validator;
importjava.util.HashSet;
importjava.util.Set;
importjavax.validation.ConstraintViolation;
importorg.springframework.beans.factory.annotation.Autowired;
importorg.springframework.validation.Errors;
importorg.springframework.validation.Validator;
importcom.packt.webstore.domain.Product;
publicclassProductValidatorimplementsValidator{
@Autowired
privatejavax.validation.ValidatorbeanValidator;
privateSet<Validator>springValidators;
publicProductValidator(){
springValidators=newHashSet<Validator>();
}
publicvoidsetSpringValidators(Set<Validator>springValidators){
this.springValidators=springValidators;
}
publicbooleansupports(Class<?>clazz){
returnProduct.class.isAssignableFrom(clazz);
}
publicvoidvalidate(Objecttarget,Errorserrors){
Set<ConstraintViolation<Object>>constraintViolations
=beanValidator.validate(target);
for(ConstraintViolation<Object>constraintViolation
:constraintViolations){
StringpropertyPath
=constraintViolation.getPropertyPath().toString();
Stringmessage=constraintViolation.getMessage();
errors.rejectValue(propertyPath,"",message);
}
for(Validatorvalidator:springValidators){
validator.validate(target,errors);
}
}
}
2. Now,openthewebapplicationcontextconfigurationfileDispatcherServlet-
context.xmlandaddthefollowingbeandefinitiontoit:
<bean
id="productValidator"class="com.packt.webstore.validator.ProductValidat
or">
<propertyname="springValidators">
<set>
<refbean="unitsInStockValidator"/>
</set>
</property>
</bean>
3. CreateonemorebeandefinitionfortheUnitsInStockValidatorclass,asfollows,
andsaveDispatcherServlet-context.xml:
<beanid="unitsInStockValidator"
class="com.packt.webstore.validator.UnitsInStockValidator"/>
4. OpentheProductControllerclassandreplacetheexistingreferenceofthe
UnitsInStockValidatorclasswiththenewlycreatedProductValidatorclass,as
follows:
@Autowired
privateProductValidatorproductValidator;
5. Now,insidetheinitialiseBindermethodoftheProductControllerclass,replace
thebinder.setValidator(unitsInStockValidator);statementwiththefollowing
statement:
binder.setValidator(productValidator);
6. Now,runtheapplicationandenter
http://localhost:8080/webstore/products/addtocheckwhetherallthe
validationsareworkingfine.JustclickontheAddbuttonwithoutfillinganythingon
theform;youwillnoticebeanvalidationtakingplace.Similarly,filltheUnitPrice
fieldwiththevalue10000andtheUnitsInStockfieldwiththevalue100tosee
Springvalidation.Considerthefollowingscreenshot:
TheAddnewproductwebformdisplayingbeanvalidationandSpringvalidation
together
Whatjusthappened?
OuraimwastocombinebeanvalidationandSpring-basedvalidation
(unitsInStockValidator)together.Toachievethis,wecreatedacommonadapter
validatorcalledProductValidatorinstep1.Ifyou’lllookclosely,theProductValidator
classisnothingbutanimplementationofaregularSpringvalidator.
WeautowiredourexistingbeanvalidatorintotheProductValidatorclassthroughthe
followingline:
@Autowired
privatejavax.validation.ValidatorbeanValidator;
Later,weusedthisbeanValidatorreferenceinsidethevalidatemethodofthe
ProductValidatorclass,asfollows,tovalidateallofthebeanvalidationannotations:
Set<ConstraintViolation<Object>>constraintViolations
=beanValidator.validate(target);
for(ConstraintViolation<Object>constraintViolation:constraintViolations)
{
StringpropertyPath=constraintViolation.getPropertyPath().toString();
Stringmessage=constraintViolation.getMessage();
errors.rejectValue(propertyPath,"",message);
}
ThebeanValidator.validate(target);statementreturnsalloftheconstraintviolations.
Then,usingtheerrorsobject,wethrewalloftheinvalidconstraintsaserrormessages.
So,everybeanvalidationannotationthatwespecifiedintheProductdomainclasswill
gethandledwithinforloop.
Similarly,wehaveonemoreforlooptohandlealloftheSpringvalidationsinthe
validatemethodoftheProductValidatorclass,asshownasfollows:
for(Validatorvalidator:springValidators){
validator.validate(target,errors);
}
ThisforloopiteratesthroughthesetofSpringvalidatorsandvalidatestheentriesoneby
one;however,ifyounotice,wehaven’tinitiatedthespringValidatorsreference,soyou
maywonderwherewehaveinitiatedthespringValidatorsset.Youcanfindtheanswer
instep2;wecreatedabeanfortheProductValidatorclassinourwebapplication
context(DispatcherServlet-context.xml)andinstantiatedthespringValidatorssetas
follows:
<bean
id="productValidtor"class="com.packt.webstore.validator.ProductValidator">
<propertyname="springValidators">
<set>
<refbean="unitsInStockValidator"/>
</set>
</property>
</bean>
WereferredabeancalledunitsInStockValidatorwithinthespringValidatorssetof
theproductValidatorbean,sowehavetocreateabeanfortheUnitsInStockValidator
class,whichiswhatwedidinstep3.
Then,wecreatedacommonadaptervalidatorthatcanadoptbeanvalidationandSpring
validationandvalidatesallSpring-andbean-basedvalidationstogether.Now,wehaveto
replacetheUnitsInStockValidatorreferencewiththeProductValidatorreferencein
ourProductControllerclasstokickinournewProductValidatorreference.Wedid
thatinsteps4and5.WesimplyreplacedUnitsInStockValidatorwith
ProductValidatorinthebinder,asfollows:
@InitBinder
publicvoidinitialiseBinder(WebDataBinderbinder){

binder.setAllowedFields("productId","name","unitPrice","description","manuf
acturer","category","unitsInStock","productImage","language");
binder.setValidator(productValidator);
}
WesuccessfullyconfiguredournewlycreatedProductValidatorwith
ProductController.Toseeitinaction,wecanjustrunourapplicationandenter
http://localhost:8080/webstore/products/add.Then,weentersomeinvalidvalues
suchastheexistingproductIDorfilltheUnitPricefieldwiththevalue10000andthe
UnitsInStockfieldwiththevalue100;youwillnoticethebeanandSpringvalidation
errormessagesonthescreen.
Haveagohero–addingSpringvalidationtothe
productimage
CreateaSpringvalidationclasscalledProductImageValidatorthatwillvalidatethesize
oftheproductimage.Itshouldonlyallowanimageofasizethatislessthanorequalto
thepredefinedconfiguredsize.Dothefollowingwhenimplementing
ProductImageValidator:
CreateavalidationclasscalledProductImageValidatorunderthe
com.packt.webstore.validatorpackagebyimplementingthe
org.springframework.validation.Validatorinterface
Addthecorrespondingerrormessageinthemessagesourcefile
YourProductImageValidatorclassshouldmaintainalongvariablecalled
allowedSizetocheckwhetherthegivenimagesizeislessthanorequalit
CreateabeanfortheProductImageValidatorclassintheservletcontextandaddit
underthespringValidatorssetoftheproductValidtorbean
RemembertosettheallowedSizepropertyintheProductImageValidatorbean
Afterapplyingyourcustomvalidationannotation@categoryonthecategoryfieldofthe
Productdomainclass,youraddproductpageshouldrejecttheproductsofother
categoriesthathavenotbeenconfiguredinCategoryValidator.
Summary
Inthischapter,welearnedtheconceptofvalidationandlearnedhowtoenablebean
validationinSpringMVCtoprocessforms.Wealsolearnedhowtosetupcustom
validationusingtheextensioncapabilityofthebeanvalidationframework.Afterthat,we
learnedhowtodocross-fieldvalidationusingSpringvalidation.Finally,welearnedhow
tointegratebeanvalidationandSpringvalidationtogether.
Inthenextchapter,wewilllearnhowtodevelopanapplicationusingRESTfulservices.
WewillcoverthebasicconceptsofHTTPverbsandtrytounderstandhowtheyare
relatedtostandardCRUDoperations.WewillalsocoverhowtofireanAjaxrequestand
howtohandleit.
Chapter8.GiveRESTtoYour
ApplicationwithAjax
RESTstandsforRepresentationalStateTransferandisastyleofwebapplication
architecture.EverythinginRESTisconsideredasaresource,andeveryresourceis
identifiedbyaURI.RESTfulwebserviceshavebeenembracedbylargeserviceproviders
acrosstheWebasanalternativetoSOAP-basedwebservicesduetoitssimplicity.
Afterfinishingthischapter,youwillhaveaclearideaaboutthefollowing:
RESTwebservices
Ajax
IntroducingREST
AsIalreadymentioned,inaREST-basedapplication,everything,includingstatic
resources,data,andoperations,areconsideredasresourcesandidentifiedbyaURI.For
example,considerapieceoffunctionalitythatcanhelpusaddanewproducttoourstore;
wecanrepresentthisoperationbyaURI,somethinglike
http://localhost:8080/webstore/products/add,andwecanpassthenewproduct
detailsinXMLorJSONrepresentationtothatURL.So,inREST,URIsareusedto
connectclientsandserverstoexchangeresourcesintheformofrepresentations(HTML,
XML,JSON,andsoon).Inordertoexchangedata,RESTreliesonbasicHTTPprotocol
methods:GET,POST,PUT,andDELETE.
SpringprovidesextensivesupporttodevelopREST-basedwebservices.Inourprevious
chapters,wesawthatwheneverawebrequestwasmade,wereturnedawebpagetoserve
thatrequest;usually,suchwebpageswillalwayscontainsomestates(dynamicdata).
However,inREST-basedapplications,weonlyreturnthestates,anditisuptotheclient
todecideonhowtorenderorpresentthedatatotheenduser.
Normally,REST-basedwebservicesreturndataintwoformats:XMLandJSON.Weare
goingtodevelopsomeREST-basedwebservicesthatwillreturndataintheJSONformat.
OncewegettheJSONdata,we’llthenrenderitasanHTMLpageinthebrowserusinga
JavaScriptlibrary.
Inourwebstoreapplication,wehavesuccessfullylistedsomeoftheproducts;however,
thestorecannotmakeprofitwithoutfacilitatingtheendusertopickupsomeproductsand
placetheminhis/hershoppingcart.Solet’saddashoppingcartfacilitytoourstore.
Timeforaction–implementingRESTful
webservices
Wearegoingtoaddashoppingcartfacilityintwophases.Firstly,wewillcreateaREST-
stylecontrollertohandleallshopping-cart-relatedwebrequests.Secondly,wewilladd
someJavaScriptcodetorendertheJSONdatareturnedbytheRESTwebservice
controller.First,let’simplementsomeRESTfulwebservicesusingSpringMVC
controllerssothatlaterwecanaddsomeJavaScriptcodetoconsumethosewebservices.
1. CreateadomainclassnamedCartItemunderthepackage
com.packt.webstore.domaininthesourcefoldersrc/main/java;then,addthe
followingcodetoit:
packagecom.packt.webstore.domain;
importjava.math.BigDecimal;
publicclassCartItem{
privateProductproduct;
privateintquantity;
privateBigDecimaltotalPrice;

publicCartItem(){
//TODOAuto-generatedconstructorstub
}

publicCartItem(Productproduct){
super();
this.product=product;
this.quantity=1;
this.totalPrice=product.getUnitPrice();
}

publicProductgetProduct(){
returnproduct;
}

publicvoidsetProduct(Productproduct){
this.product=product;
this.updateTotalPrice();
}

publicintgetQuantity(){
returnquantity;
}

publicvoidsetQuantity(intquantity){
this.quantity=quantity;
this.updateTotalPrice();
}

publicBigDecimalgetTotalPrice(){
returntotalPrice;
}

publicvoidupdateTotalPrice(){
totalPrice=
this.product.getUnitPrice().multiply(newBigDecimal(this.quantity));
}

@Override
publicinthashCode(){
finalintprime=311;
intresult=1;
result=prime*result+((product==null)?0
:product.hashCode());
returnresult;
}
@Override
publicbooleanequals(Objectobj){
if(this==obj)
returntrue;
if(obj==null)
returnfalse;
if(getClass()!=obj.getClass())
returnfalse;
CartItemother=(CartItem)obj;
if(product==null){
if(other.product!=null)
returnfalse;
}elseif(!product.equals(other.product))
returnfalse;
returntrue;
}
}
2. Similarly,addonemoredomainclassnamedCarttothesamepackage,andaddthe
followingcodetoit:
packagecom.packt.webstore.domain;
importjava.math.BigDecimal;
importjava.util.HashMap;
importjava.util.Map;
publicclassCart{
privateStringcartId;
privateMap<String,CartItem>cartItems;
privateBigDecimalgrandTotal;

publicCart(){
cartItems=newHashMap<String,CartItem>();
grandTotal=newBigDecimal(0);
}

publicCart(StringcartId){
this();
this.cartId=cartId;
}

publicStringgetCartId(){
returncartId;
}

publicvoidsetCartId(StringcartId){
this.cartId=cartId;
}

publicMap<String,CartItem>getCartItems(){
returncartItems;
}

publicvoidsetCartItems(Map<String,CartItem>cartItems){
this.cartItems=cartItems;
}

publicBigDecimalgetGrandTotal(){
returngrandTotal;
}

publicvoidaddCartItem(CartItemitem){
StringproductId=item.getProduct().getProductId();

if(cartItems.containsKey(productId)){
CartItemexistingCartItem=cartItems.get(productId);
existingCartItem.setQuantity(existingCartItem.getQuantity()+
item.getQuantity());
cartItems.put(productId,existingCartItem);
}else{
cartItems.put(productId,item);
}
updateGrandTotal();
}

publicvoidremoveCartItem(CartItemitem){
StringproductId=item.getProduct().getProductId();
cartItems.remove(productId);
updateGrandTotal();
}

publicvoidupdateGrandTotal(){
grandTotal=newBigDecimal(0);
for(CartItemitem:cartItems.values()){
grandTotal=grandTotal.add(item.getTotalPrice());
}
}

@Override
publicinthashCode(){
finalintprime=71;
intresult=1;
result=prime*result+((cartId==null)?0
:cartId.hashCode());
returnresult;
}

@Override
publicbooleanequals(Objectobj){
if(this==obj)
returntrue;
if(obj==null)
returnfalse;
if(getClass()!=obj.getClass())
returnfalse;
Cartother=(Cart)obj;
if(cartId==null){
if(other.cartId!=null)
returnfalse;
}elseif(!cartId.equals(other.cartId))
returnfalse;
returntrue;
}
}
3. CreateaninterfacenamedCartRepositoryunderthepackage
com.packt.webstore.domain.repositoryinthesourcefoldersrc/main/java;then,
addthefollowingmethoddeclarationstoit:
Cartcreate(Cartcart);
Cartread(StringcartId);
voidupdate(StringcartId,Cartcart);
voiddelete(StringcartId);
4. CreateanimplementationclassnamedInMemoryCartRepositoryforthepreceding
interfaceunderthepackagecom.packt.webstore.domain.repository.implinthe
sourcefoldersrc/main/java;then,addthefollowingcodetoit:
packagecom.packt.webstore.domain.repository.impl;
importjava.util.HashMap;
importjava.util.Map;
importorg.springframework.stereotype.Repository;
importcom.packt.webstore.domain.Cart;
importcom.packt.webstore.domain.repository.CartRepository;
@Repository
publicclassInMemoryCartRepositoryimplementsCartRepository{

privateMap<String,Cart>listOfCarts;


publicInMemoryCartRepository(){
listOfCarts=newHashMap<String,Cart>();

}

publicCartcreate(Cartcart){
if(listOfCarts.keySet().contains(cart.getCartId())){
thrownewIllegalArgumentException(String.format("Cannotcreate
acart.Acartwiththegiveid(%)aldradyexist",cart.getCartId()));
}
listOfCarts.put(cart.getCartId(),cart);
returncart;
}

publicCartread(StringcartId){
returnlistOfCarts.get(cartId);
}
publicvoidupdate(StringcartId,Cartcart){
if(!listOfCarts.keySet().contains(cartId)){
thrownewIllegalArgumentException(String.format("Cannotupdate
cart.Thecartwiththegiveid(%)doesnotdoesnotexist",cartId));
}
listOfCarts.put(cartId,cart);
}
publicvoiddelete(StringcartId){
if(!listOfCarts.keySet().contains(cartId)){
thrownewIllegalArgumentException(String.format("Cannotdelete
cart.Thecartwiththegiveid(%)doesnotdoesnotexist",cartId));
}
listOfCarts.remove(cartId);
}
}
5. CreateaninterfacenamedCartServiceunderthepackage
com.packt.webstore.serviceinthesourcefoldersrc/main/java;then,addthe
followingmethoddeclarationstoit:
packagecom.packt.webstore.service;
importcom.packt.webstore.domain.Cart;
publicinterfaceCartService{

Cartcreate(Cartcart);

Cartread(StringcartId);

voidupdate(StringcartId,Cartcart);

voiddelete(StringcartId);
}
6. CreateanimplementationclassnamedCartServiceImplfortheearlierinterface
underthepackagecom.packt.webstore.service.implinthesourcefolder
src/main/java;then,addthefollowingcodetoit:
packagecom.packt.webstore.service.impl;
importorg.springframework.beans.factory.annotation.Autowired;
importorg.springframework.stereotype.Service;
importorg.springframework.transaction.annotation.Transactional;
importcom.packt.webstore.domain.Cart;
importcom.packt.webstore.domain.repository.CartRepository;
importcom.packt.webstore.service.CartService;
@Service
publicclassCartServiceImplimplementsCartService{

@Autowired
privateCartRepositorycartRepository;
publicCartcreate(Cartcart){
returncartRepository.create(cart);
}
publicCartread(StringcartId){
returncartRepository.read(cartId);
}
publicvoidupdate(StringcartId,Cartcart){
cartRepository.update(cartId,cart);
}
publicvoiddelete(StringcartId){
cartRepository.delete(cartId);

}
}
7. Now,createaclassnamedCartRestControllerunderthepackage
com.packt.webstore.controllerinthesourcefoldersrc/main/java;then,addthe
followingcodetoit:
packagecom.packt.webstore.controller;
importjavax.servlet.http.HttpServletRequest;
importorg.springframework.beans.factory.annotation.Autowired;
importorg.springframework.http.HttpStatus;
importorg.springframework.stereotype.Controller;
importorg.springframework.web.bind.annotation.ExceptionHandler;
importorg.springframework.web.bind.annotation.PathVariable;
importorg.springframework.web.bind.annotation.RequestBody;
importorg.springframework.web.bind.annotation.RequestMapping;
importorg.springframework.web.bind.annotation.RequestMethod;
importorg.springframework.web.bind.annotation.ResponseBody;
importorg.springframework.web.bind.annotation.ResponseStatus;
importcom.packt.webstore.domain.Cart;
importcom.packt.webstore.domain.CartItem;
importcom.packt.webstore.domain.Product;
importcom.packt.webstore.exception.ProductNotFoundException;
importcom.packt.webstore.service.CartService;
importcom.packt.webstore.service.ProductService;
@Controller
@RequestMapping(value="rest/cart")
publicclassCartRestController{
@Autowired
privateCartServicecartService;

@Autowired
privateProductServiceproductService;

@RequestMapping(method=RequestMethod.POST)
public@ResponseBodyCartcreate(@RequestBodyCartcart){
returncartService.create(cart);
}
@RequestMapping(value="/{cartId}",method=RequestMethod.GET)
public@ResponseBodyCartread(@PathVariable(value="cartId")String
cartId){
returncartService.read(cartId);
}
@RequestMapping(value="/{cartId}",method=RequestMethod.PUT)
@ResponseStatus(value=HttpStatus.NO_CONTENT)
publicvoidupdate(@PathVariable(value="cartId")StringcartId,
@RequestBodyCartcart){
cartService.update(cartId,cart);
}
@RequestMapping(value="/{cartId}",method=RequestMethod.DELETE)
@ResponseStatus(value=HttpStatus.NO_CONTENT)
publicvoiddelete(@PathVariable(value="cartId")StringcartId){
cartService.delete(cartId);
}

@RequestMapping(value="/add/{productId}",method=
RequestMethod.PUT)
@ResponseStatus(value=HttpStatus.NO_CONTENT)
publicvoidaddItem(@PathVariableStringproductId,
HttpServletRequestrequest){

StringsessionId=request.getSession(true).getId();
Cartcart=cartService.read(sessionId);
if(cart==null){
cart=cartService.create(newCart(sessionId));
}

Productproduct=productService.getProductById(productId);
if(product==null){
thrownewIllegalArgumentException(new
ProductNotFoundException(productId));
}

cart.addCartItem(newCartItem(product));

cartService.update(sessionId,cart);
}

@RequestMapping(value="/remove/{productId}",method=
RequestMethod.PUT)
@ResponseStatus(value=HttpStatus.NO_CONTENT)
publicvoidremoveItem(@PathVariableStringproductId,
HttpServletRequestrequest){

StringsessionId=request.getSession(true).getId();
Cartcart=cartService.read(sessionId);
if(cart==null){
cart=cartService.create(newCart(sessionId));
}

Productproduct=productService.getProductById(productId);
if(product==null){
thrownewIllegalArgumentException(new
ProductNotFoundException(productId));
}

cart.removeCartItem(newCartItem(product));

cartService.update(sessionId,cart);
}
@ExceptionHandler(IllegalArgumentException.class)
@ResponseStatus(value=HttpStatus.BAD_REQUEST,reason="Illegal
request,pleaseverifyyourpayload")
publicvoidhandleClientErrors(Exceptionex){}
@ExceptionHandler(Exception.class)
@ResponseStatus(value=HttpStatus.INTERNAL_SERVER_ERROR,
reason="Internalservererror")
publicvoidhandleServerErrors(Exceptionex){}
}
8. Now,runourwebstoreprojectfromSTS.
Whatjusthappened?
Instep1and2,wecreatedtwodomainclassescalledCartItemandCarttoholdthe
informationabouttheshoppingcart.TheCartItemclassrepresentsasingleitemina
shoppingcart,anditholdsinformationsuchasproduct,quantity,andtotalPrice.
Similarly,Cartrepresentsthewholeshoppingcartitself,andCartcanhaveacollectionof
cartItemsandgrandTotal.
Insteps3and4,wecreatedarepositorylayertomanagetheCartobjects.Inthe
CartRepositoryinterface,wedefinedfourmethodstotakecareofCRUDoperations
(create,read,update,anddelete)ontheCartobjects.InMemoryCartRepositoryisjust
animplementationofCartRepository.
Similarly,insteps5and6,wecreatedtheservicelayerfortheCartobjects.The
CartServiceinterfacehasthesamemethodsasthatoftheCartRepositoryand
CartServiceImplclass;theonlydifferenceisthatitinternallyuses
InMemoryCartRepositorytocarryoutalltheCRUDoperations.
Step7isverycrucialinthewholesequencebecauseinthatstepwecreatedourREST-
styledcontrollertohandleallRESTwebservicesrelatedtoCart.The
CartRestControllerclassmainlyhasfourmethodstohandlewebrequestsforCRUD
operationsontheCartobjects,namelycreate,read,update,anddelete.Additionally,it
hastwomethods,addItemandremoveItem,tohandletheaddingandremovingof
CartItemfromtheCartobjects.WewillhaveadeeperlookatthefirstfourCRUD
methods.
Ifyousee,onthesurface,theCartRestControllerclassisjustlikeanyothernormal
SpringMVCcontrollerbecauseitjusthasthesame@Controllerand@RequestMapping
annotations.SowhatmakesitsospecialtobecomeaREST-styledcontrolleristhe
@ResponseBodyand@RequestBodyannotations;seethefollowingcontrollermethod:
@RequestMapping(method=RequestMethod.POST)
public@ResponseBodyCartcreate(@RequestBodyCartcart){
returncartService.create(cart);
}
Usually,everycontrollermethodisusedtoreturnaviewnamesothatthedispatcher
servletcanfindtheappropriateviewfileanddispatchthatviewfiletotheclient,buthere
wehavereturnedtheobject(theCartobject).Insteadofputtingtheobjectintothemodel,
wehavereturnedtheobjectbecausewewanttoreturnthestateoftheobjectinJSON
format.RememberthatREST-basedwebservicesshouldreturndataineitherJSONor
XMLformat,andtheclientcanusethisdataintheirdesiredway;theymayrenderittoan
HTMLpage,ortheymaysendittosomeexternalsystemasisintheformofraw
JSON/XMLdata.
Okay!Let’scometothepoint;thecreatecontrollermethodjustreturnedanewlycreated
Cartjavaobject.HowisitthatthisJavaobjectgotconvertedintoJSONorXMLformat?
Here,the@ResponseBodyannotationstepsintothepicture.The@ResponseBodyannotation
willconvertthegivenJavaobjectintoJSON/XMLformatandsenditasaresponseinthe
bodyofanHTTPresponse.Similarly,whenyousendanHTTPrequesttoacontroller
methodwithJSON/XMLdatainit,the@RequestBodyannotationwillconvertitintothe
correspondingJavaobject.Thisiswhythecreatemethodhasthecartparameter
annotatedwiththe@RequestBodyannotationandthereturnobjectannotatedwiththe
@ResponseBodyannotation.
Ifyoucloselyobservethe@RequestMappingannotationofallthosefourCRUDmethods,
youwillendupwiththefollowingtable:
URL HTTPmethod Description
http://localhost:8080/webstore/rest/cart POST Createsanewcart
http://localhost:8080/webstore/rest/cart/1234 GET RetrievescartwiththeID1234
http://localhost:8080/webstore/rest/cart/1234 PUT UpdatescartwiththeID1234
http://localhost:8080/webstore/rest/cart/1234 DELETE DeletescartwiththeID1234
ThoughtherequestmappingURLismoreorlessthesame,wecanperformdifferent
operationsbasedontheHTTPmethod;forexample,ifyousendaGETrequesttothe
URLhttp://localhost:8080/webstore/rest/cart/1234,thereadcontrollermethod
willgetexecutedandtheCartobjectwiththeID1234willgetreturnedintheJSON
format.Similarly,ifyousendaPUTorDELETErequesttothesameURL,theupdateor
deletecontrollermethodwouldgetcalledcorrespondingly.
InadditiontothosefourCRUDrequest-mappingmethods,wehavetwomorerequest-
mappingmethodsthattakecareofaddingandremovingCartItemfromtheCartobject.
Thesemethodsareconsideredasupdatemethods;thisiswhyboththeaddItemand
removeItemmethodshavePUTastherequestmethodtypeintheir@RequestMapping
annotation.Forinstance,ifyousendaPUTrequesttotheURL
http://localhost:8080/webstore/rest/cart/add/P1236,aproductwiththeproductID
P1236willbeaddedtotheCartobject.Similarly,ifyousendaPUTrequesttotheURL
http://localhost:8080/webstore/rest/cart/remove/P1236,aproductwithP1236will
beremovedfromtheCartobject.
Timeforaction–consumingRESTweb
services
Okay!WehavecreatedourREST-stylecontrollerthatcanservesomeREST-basedweb
requests,butwehavenotseenourCartRestControllerclassinaction.Usingastandard
browser,wecanonlysendGETorPOSTrequests;inordertosendaPUTorDELETErequest,
weneedaspecialtool.ThereareplentyofHTTPclienttoolsavailabletosendsuch
requests.Let’suseonesuchtoolcalledPostmantotestourCartRestController.Postman
isaGoogleChromebrowserextension,soyou’dbetterinstallGoogleChromeinyour
systembeforeyoudownloadthePostmanHTTPclient.Performthefollowingsteps:
1. GotothePostmandownloadpage,http://www.getpostman.com/,fromyourGoogle
ChromebrowserandclickontheDownloadPostmanlink.Itwilltakeyoutothe
Chromewebstorepage;clickonthe+FREEbuttontoinstallthePostmantoolin
yourbrowser.Considerthefollowingscreenshot:
Postman—HTTPclientappinstallation
2. Now,aGoogleloginpagewillappearaskingyoutologin.LoginusingyourGoogle
account.
3. Aconfirmdialogwillbeshownonyourscreenaskingyourpermissiontoaddthe
Postmanextensiontoyourbrowser;clickontheAddbuttonasshowninthe
followingscreenshot:
Postman—HTTPclientappinstallation
4. NowopenyourGoogleChromebrowserandentertheURL,chrome://apps/.Aweb
pagewillgetloadedwithalltheavailableappsforyourChromebrowser.Justclick
onthePostmanicontolaunchthePostmanapp.BeforeyoulaunchPostman,ensure
thatyourwebstoreprojectisrunning.
5. Now,inthePostmanapp,entertherequestURLas
http://localhost:8080/webstore/rest/cart,therequestmethodasPOST,then
selecttherawformat,andfinallythecontenttypeasJSON(application/json).
Considerthefollowingscreenshot:
Postman–postingawebrequest
6. Now,enterthefollowingJSONcontentinthecontentboxandclickontheSend
button.YouwillgetHTTPrespondstatus200OK.Considerthefollowingcode
snippet:
{
"cartId":"1234",
"cartItems":{
"P1234":{
"product":{
"productId":"P1234",
"name":"iPhone5s",
"unitPrice":500,
"description":"AppleiPhone5ssmartphonewith4.00-inch
640x1136displayand8-megapixelrearcamera",
"manufacturer":"Apple",
"category":"SmartPhone",
"unitsInStock":1000,
"unitsInOrder":0,
"discontinued":false,
"condition":"NEW"
},
"quantity":1,
"totalPrice":500
}
},
"grandTotal":500
}
7. Now,similarlyinthePostmanapp,enterthetargetURLas
http://localhost:8080/webstore/rest/cart/1234,therequestmethodasGET,
andclickontheSendbutton.YouwillgetthesameJSONcartdatathatyoujust
postedinstep7astheresponse.
8. Toupdatethecart,inthePostmanapp,enterthetargetURLas
http://localhost:8080/webstore/rest/cart/1234andjustchangetheJSONdata.
Forinstance,inthecontentbox,justchangequantityto3,totalPriceto1500and
grandTotalto1500,choosetherequestmethodasPUTandthecontenttypeas
JSON(application/json),andsendtherequesttothesameURLbyclickingonthe
Sendbutton.Toverifywhetheryourchangestookplace,justrepeatstep7.Consider
thefollowingcodesnippet:
{
"cartId":"1234",
"cartItems":{
"P1234":{
"product":{
"productId":"P1234",
"name":"iPhone5s",
"unitPrice":500,
"description":"AppleiPhone5ssmartphonewith4.00-inch
640x1136displayand8-megapixelrearcamera",
"manufacturer":"Apple",
"category":"SmartPhone",
"unitsInStock":1000,
"unitsInOrder":0,
"discontinued":false,
"condition":"NEW"
},
"quantity":3,
"totalPrice":1500
}
},
"grandTotal":1500
}
9. Similarly,todeletethecart,justenterthe
http://localhost:8080/webstore/rest/cart/1234URL.InthePostmanapp,
enterthetargetURLandrequestmethodasDELETEandclickontheSendbutton.
YouwillgetanHTTPstatus204NoContentastheresponse.Toverifywhetherthe
cartgotdeleted,justrepeatstep7;youwillgetanemptyresponse.
Whatjusthappened?
Atthestartofthechapter,wediscussedthatmostoftheREST-basedwebservicesare
designedtoexchangedatainJSONorXMLformat.ThisisbecauseJSONandXML
formatsareconsideredtobeuniversalformats,andanysystemcaneasilyunderstand,
parse,andinterpretthatdata.InordertotestREST-basedwebservicesthatwehave
created,weneedatoolthatcansenddifferent(GET,PUT,POST,orDELETE)typesofHTTP
requestswithJSONdatainitsrequestbody.Postmanisonesuchtoolthatisavailableasa
GoogleChromeextension.
Fromstep1to4,weinstalledthePostmanappinourGoogleChromebrowser.Instep6
wesentourfirstREST-basedwebrequesttothetargetURL
http://localhost:8080/webstore/rest/carttocreateanewcartinourwebstore
application.WedidthisbysendingaPOSTrequestwiththewholecartinformationas
JSONdatatothetargetURL.IfyounoticethefollowingJSONdata,itrepresentsacart
withthecartIDas1234,andithasjustoneproductcartitem(iPhone5s)init.Consider
thefollowingcodesnippet:
{
"cartId":"1234",
"cartItems":{
"P1234":{
"product":{
"productId":"P1234",
"name":"iPhone5s",
"unitPrice":500,
"description":"AppleiPhone5ssmartphonewith4.00-inch640x1136
displayand8-megapixelrearcamera",
"manufacturer":"Apple",
"category":"SmartPhone",
"unitsInStock":1000,
"unitsInOrder":0,
"discontinued":false,
"condition":"NEW"
},
"quantity":1,
"totalPrice":500
}
},
"grandTotal":500
}
Nowthatwehavepostedourfirstcart,toverifywhetherthatcartgotstoredinoursystem,
wehavesentanotherRESTwebrequestinstep7togetthewholecartinformationin
JSONformat.NoticethatthistimetherequesttypeisGETandthetargetURLis
http://localhost:8080/webstore/rest/cart/1234.Rememberwelearnedthatina
REST-basedapplication,everyresourceisidentifiablebyaURI.Here,theURL
http://localhost:8080/webstore/rest/cart/1234representsacartwhoseIDis1234.
IfyousendaGETrequesttotheURLmentionedearlier,youwillgetthecartinformation
intheformofJSONdata;similarly,youcanevenupdatethewholecartbysendingan
updatedJSONdataasaPUTrequesttothesameURL.Thisiswhatwedidinstep8.Ina
similarfashion,wesentaDELETErequesttothesameURLtodeletethecartwhoseIDis
1234.
Okay!WehavetestedorconsumedourREST-basedwebserviceswiththehelpofthe
PostmanHTTPclienttool,whichisworkingquitewell.However,inareal-world
application,mostofthetime,thesekindsofREST-basedwebservicesareconsumedfrom
thefrontendwiththehelpofaconceptcalledAjax.UsingaJavaScriptlibrary,wecan
sendanAjaxrequesttothebackend.Inthenextsection,wewillseewhatAjaxrequests
areandhowtoconsumeaREST-basedwebserviceusingJavaScript/Ajaxlibraries.
HandlingawebserviceinAjax
AsynchronousJavaScriptandXML(Ajax)isawebdevelopmenttechniqueusedonthe
clientsidetocreateasynchronouswebapplications.Inatypicalwebapplication,every
timeawebrequestisfiredasaresponse,wegetafullwebpageloadedasaresponse;
however,inanAjax-basedasynchronouswebapplication,webpagesareupdated
asynchronouslybypollingsmalldatawiththeserverbehindthescenes.Thismeansthat
usingAjax,itispossibletoupdatepartsofawebpagewithoutreloadingtheentireweb
page.WithAjax,webapplicationscansenddatatoandretrievedatafromaserver
asynchronously.TheasynchronousaspectofAjaxallowsustowritecodethatcansenda
requesttoaserverandhandleaserverresponsewithoutreloadingtheentirewebpage.
InanAjax-basedapplication,theXMLHttpRequestobjectisusedtoexchangedata
asynchronouslywiththeserver,whereXMLorJSONisoftenusedastheformatfor
transferringdata.The“X”inAJAXstandsforXML,butJSONisusedinsteadofXML
nowadaysbecauseofitssimplicity;also,itusesfewercharacterstorepresentthesame
datacomparedtoXML.So,itcanreducethebandwidthrequirementsoverthenetworkto
ensuredatatransferisfasterthannormal.
Okay!WehaveimplementedsomeREST-basedwebservicesthatcanmanagethe
shoppingcartinourapplication,butweneedafrontendthatcanfacilitatetheenduserto
managetheshoppingcartvisually.So,let’sconsumethosewebservicesviaAjaxinthe
frontendtomanagetheshoppingcart.
Timeforaction–consumingRESTweb
servicesviaAjax
InordertoconsumeRestwebservicesviaAjax,performthefollowingsteps:
1. AddaJavaScriptfilenamedcontrollers.jsunderthedirectory
/src/main/webapp/resources/js/;then,addthefollowingcodesnippetstoitand
saveit:
varcartApp=angular.module('cartApp',[]);
cartApp.controller('cartCtrl',function($scope,$http){

$scope.refreshCart=function(cartId){
$http.get('/webstore/rest/cart/'+$scope.cartId)
.success(function(data){
$scope.cart=data;
});
};

$scope.clearCart=function(){
$http.delete('/webstore/rest/cart/'+$scope.cartId)
.success($scope.refreshCart($scope.cartId));

};

$scope.initCartId=function(cartId){
$scope.cartId=cartId;
$scope.refreshCart($scope.cartId);
};

$scope.addToCart=function(productId){
$http.put('/webstore/rest/cart/add/'+productId)
.success(function(data){
$scope.refreshCart($http.get('/webstore/rest/cart/get/cartId'));
alert("ProductSuccessfullyaddedtotheCart!");
});
};
$scope.removeFromCart=function(productId){
$http.put('/webstore/rest/cart/remove/'+productId)
.success(function(data){
$scope.refreshCart($http.get('/webstore/rest/cart/get/cartId'));
});
};
});
2. Now,createaclassnamedCartControllerunderthepackage
com.packt.webstore.controllerinthesourcefoldersrc/main/java;then,addthe
followingcodetoit:
packagecom.packt.webstore.controller;
importjavax.servlet.http.HttpServletRequest;
importorg.springframework.stereotype.Controller;
importorg.springframework.ui.Model;
importorg.springframework.web.bind.annotation.PathVariable;
importorg.springframework.web.bind.annotation.RequestMapping;
importorg.springframework.web.bind.annotation.RequestMethod;
@Controller
@RequestMapping(value="/cart")
publicclassCartController{
@RequestMapping
publicStringget(HttpServletRequestrequest){
return"redirect:/cart/"+request.getSession(true).getId();
}

@RequestMapping(value="/{cartId}",method=RequestMethod.GET)
publicStringgetCart(@PathVariable(value="cartId")StringcartId,
Modelmodel){
model.addAttribute("cartId",cartId);
return"cart";
}
}
3. AddonemoreJSPviewfilenamedcart.jspunderthedirectory
src/main/webapp/WEB-INF/views/;then,addthefollowingcodesnippetstoitand
saveit:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
<html>
<head>
<metahttp-equiv="Content-Type"content="text/html;charset=ISO-8859-
1">
<linkrel="stylesheet"

href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<script
src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.1/angular.min.
js"></script>
<scriptsrc="/webstore/resource/js/controllers.js"></script>
<title>Cart</title>
</head>
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1>Cart</h1>
<p>Alltheselectedproductsinyourcart</p>
</div>
</div>
</section>
<sectionclass="container"ng-app="cartApp">
<divng-controller="cartCtrl"ng-init="initCartId('${cartId}')">
<div>
<aclass="btnbtn-dangerpull-left"
ng-click="clearCart()"><span
class="glyphiconglyphicon-remove-sign"></span>ClearCart
</a><ahref="#"class="btnbtn-successpull-right"><span
class="glyphicon-shopping-cartglyphicon"></span>Checkout
</a>
</div>
<tableclass="tabletable-hover">
<tr>
<th>Product</th>
<th>Unitprice</th>
<th>Qauntity</th>
<th>Price</th>
<th>Action</th>
</tr>
<trng-repeat="itemincart.cartItems">
<td>{{item.product.productId}}-{{item.product.name}}</td>
<td>{{item.product.unitPrice}}</td>
<td>{{item.quantity}}</td>
<td>{{item.totalPrice}}</td>
<td><ahref="#"class="labellabel-danger"ng-
click="removeFromCart(item.product.productId)"><span
class="glyphiconglyphicon-remove"/></span>Remove
</a></td>
</tr>
<tr>
<th></th>
<th></th>
<th>GrandTotal</th>
<th>{{cart.grandTotal}}</th>
<th></th>
</tr>
</table>

<ahref="<spring:urlvalue="/products"/>"class="btnbtn-
default">
<spanclass="glyphicon-hand-leftglyphicon"></span>
Continueshopping
</a>
</div>
</section>
</body>
</html>
4. Openproduct.jspfromsrc/main/webapp/WEB-INF/views/andaddthefollowing
AngularJS-relatedscriptlinksintheheadsectionasfollows:
<script
src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.1/angular.min.
js">
</script>
5. Similarly,inthesameheadsectionaddonemorescriptlinkstoourcontroller.js
inthefollowingmanner:
<scriptsrc="/webstore/resource/js/controllers.js"></script>
6. Now,addtheng-clickAngularJsdirectivetotheOrderNow<a>tagasfollows:
<ahref="#"class="btnbtn-warningbtn-large"ng-
click="addToCart('${product.productId}')">
<spanclass="glyphicon-shopping-cartglyphicon"></span>OrderNow
</a>
7. Finally,addonemore<a>tagasfollowsbesidestheOrderNow<a>tagtoshowthe
ViewCartbutton,thensavetheproduct.jsppage:
<ahref="<spring:urlvalue="/cart"/>"class="btnbtn-default">
<spanclass="glyphicon-hand-rightglyphicon"></span>ViewCart
</a>
8. Nowaddtheng-appAngularJSdirectivetotheOrderNow<section>tagas
follows:
<sectionclass="container"ng-app="cartApp">
9. Then,addtheng-controllerAngularJSdirectivetothesurrounding<p>tagofthe
OrderNowlinkasfollows:
<png-controller="cartCtrl">
10. Now,runyourapplicationandentertheURL
http://localhost:8080/webstore/products/product?id=P1234.Youwillbeable
toseetheproductdetailspageofaproductwhoseproductIDisP1234.
11. NowclickontheOrderNowbutton;analertmessagewillbeshownthatsays
Productsuccessfullyaddedtothecart!!.
12. Now,clickontheViewCartbutton;youwillseeawebpagethatshowsashopping
cartpage,asshowninthefollowingscreenshot:
Theshoppingcartpage
Whatjusthappened?
ThereareplentyofJavaScriptframeworksavailabletosendanAjaxrequesttotheserver;
wedecidedtouseAngularJs(http://angularjs.org/)asourfrontendJavaScriptlibraryto
sendAjaxrequests.ItalsohastheconceptsofModel,View,Controller,andsoon,butthe
onlydifferenceisthatitisdesignedtoworkinthefrontendusingJavaScript.
Instep1,wecreatedourAngularJS-basedcontrollercalledcontrollers.jsin
/src/main/webapp/resources/js/.Rememberthatwepurposelyputthisfileunderthe
resourcesdirectorybecausefromtheclientside,wewanttoaccessthisfileasastatic
resource;wedon’twanttogothroughSpringMVCcontrollersinordertogetthisfile.If
youremembercorrectly,wehavealreadyconfiguredthelocationoftheSpringMVC’s
resourcesinDispatcherServlet-context.xmlinthepreviouschapters;itwasdoneinthe
followingmanner:
<mvc:resourceslocation="/resources/"mapping="/resource/**"/>
Okay!Let’sgettothepoint;whathavewewrittenincontrollers.js?Wehavewritten
fivefrontendcontrollermethods,namelyrefreshCart,clearCart,initCartId,
addToCart,andremoveFromCart.Thesemethodsareusedtocommunicatewiththeserver
usingAjaxcalls.Forexample,considerthefollowingcontrollermethod:
$scope.refreshCart=function(cartId){
$http.get('/webstore/rest/cart/'+$scope.cartId)
.success(function(data){
$scope.cart=data;
});
};
WithintherefreshCartmethod,usingAngularJS’$httpobject,wesentanHTTPGET
requesttotheURItemplate/webstore/rest/cart/'+$scope.cartId.Basedonthevalue
storedinthe$scope.cartIdvariable,theactualrequestissenttothetargetRESTURL.
Forinstance,if$scope.cartIdcontainsavalueof1234,thenaGETrequestwillbesentto
http://localhost:8080/webstore/rest/cart/1234togetacartobjectasJSONdata
whoseIDis1234.OncewegotthecartobjectasJSONdata,westoreditinthefrontend
Angularmodelusingthe$scopeobjectasfollows:
.success(function(data){
$scope.cart=data;
}
Similarly,allotherAngularJScontrollermethodsfiresomeAjaxwebrequeststothe
server,andretrieveorupdatecart.Forexample,theaddToCartandremoveFromCart
methodsjustaddedcartItemandremovedcartItemfromthecartobject.
WehavejustdefinedourAngularJScontrollermethods,butwehavetoinvokethis
methodinordertodosomethinguseful.Thisiswhatwedidinstep2;wejustdefinedour
regularSpringMVCcontrollernamedCartController,whichhastworequestmapping
methods,namelygetandgetCart.WheneverausualwebrequestcomestotheURL
http://localhost:8080/webstore/cart,thegetmethodwillbeinvoked,andinsidethe
getmethod,weretrievedthesessionIDanduseditasacartIDtoinvokethegetCart
method.HerewemaintainedthesessionIDasacartID.Considerthefollowingcode
snippet:
@RequestMapping
publicStringget(HttpServletRequestrequest){
return"redirect:/cart/"+request.getSession(true).getId();
}
WithinthegetCartmethod,wesimplystoredcartIdintheSpringMVCmodeland
returnedaviewnameascart.Wedidthiskindofsetupbecausewewantourapplication
toredirecttherequesttothecorrectcartbasedonthesessionIDwheneverarequest
comestohttp://localhost:8080/webstore/cart.Sincewehavereturnedaviewname
ascart,ourdispatcherservletdefinitelywouldlookforaviewfilecalledcart.jsp.This
iswhywecreatedthecart.jspfileinstep3.
Thecart.jspfilejustactsasatemplateforourshoppingcartpage.Thecart.jsppage
internallyusestheAngularJscontroller’smethodsthatwecreatedinstep1to
communicatewiththeserver.Theng-repeatdirectiveofAngularJSwouldrepeatthe
HTMLtablerowsdynamicallybasedoncartItemsthatareavailableincart:
<trng-repeat="itemincart.cartItems">
<td>{{item.product.productId}}-{{item.product.name}}</td>
<td>{{item.product.unitPrice}}</td>
<td>{{item.quantity}}</td>
<td>{{item.totalPrice}}</td>
<td><ahref="#"class="labellabel-danger"ng-
click="removeFromCart(item.product.productId)">
<spanclass="glyphiconglyphicon-remove"/></span>Remove
</a></td>
</tr>
Theng-clickdirectivefromtheremove<a>tagwillcalltheremoveFromCartcontroller
method.Similarly,toaddcartItemtothecart,inproduct.jsp,weaddedanotherng-
clickdirectiveinstep6toinvoketheaddToCartmethod;wedidthisinthefollowing
manner:
<ahref="#"class="btnbtn-warningbtn-large"ng-
click="addToCart('${product.productId}')"><span
class="glyphicon-shopping-cartglyphicon"></span>OrderNow
</a>
Sothat’sit!Wehavedoneeverythingtorolloutourshoppingcartinourapplication,
Afterrunningourapplication,wecanaccessourshoppingcartundertheURL
http://localhost:8080/webstore/cartandwecanevenaddproductstothecartfrom
eachproductdetailspageaswell.
Summary
Inthischapter,welearnedhowtodevelopREST-basedwebservicesusingSpringMVC,
andwealsolearnedhowtotestthosewebservicesusingthePostmanHTTPclienttool.
WealsocoveredthebasicconceptsofHTTPverbsandunderstoodhowitisrelatedto
standardCRUDoperations.Finally,welearnedhowtousetheAngularJsJavaScript
frameworktosendanAjaxrequesttoourserver.
Inthenextchapter,wewillseehowtointegratetilesandwebflowframeworks.
Chapter9.ApacheTilesandSpringWeb
FlowinAction
Whenitcomestowebapplicationdevelopment,reusabilityandmaintenancearetwo
importantfactorsthatneedtobeconsidered.SpringWebFlowisanindependent
frameworkthatfacilitatesyoutodevelophighlyconfigurableandmaintainableflow-
basedwebapplications.Ontheotherhand,ApacheTilesisanotherpopularopensource
frameworkthatencouragestheuseofreusabletemplate-basedwebapplication
development.
Inthischapter,wearegoingtolearnhowtoincorporatethesetwoframeworkswithina
SpringMVCapplicationsothatwecanobtainmaximumreusabilityoffrontendtemplates
withthehelpofApacheTilesandlessmaintenanceinourapplicationlogicwiththehelp
ofSpringWebFlow.Again,rememberthatthesetwoframeworksaretotallyindependent;
thereisnorequirementthatweshouldalwaysusetheseframeworkstogether.Apache
Tilesismostlyusedtoreduceredundantcodeinthefrontendbyleveragingfrontend
templates,whereasSpringWebFlowfacilitatesthedevelopmentofastatefulweb
applicationwithcontrollednavigationflow.Afterfinishingthischapter,youwillhavea
clearideaaboutthefollowingconcepts:
Developingflow-basedapplicationsusingSpringWebFlow
DecomposingpagesusingreusableApacheTilestemplates
WorkingwithSpringWebFlow
SpringWebFlowfacilitatesustodevelopaflow-basedwebapplicationeasily.Aflowina
webapplicationencapsulatesaseriesofstepsthatguidesauserthroughtheexecutionofa
businesstask,suchascheckingintoahotel,applyingforajob,andshoppingcart
checkout.Usually,aflowwillhaveaclearstartandendpoint.ItincludesmultipleHTTP
requests/responses,andtheusermustgothroughasetofscreensinaspecificorderto
completetheflow.
Inallourpreviouschapters—theresponsibilityofdefiningthepage(userinterface)flow
specificallyliesoncontrollers—weweavedthepageflowsintoindividualcontrollersand
views;forinstance,weusuallymappedawebrequesttoacontroller,andthecontroller
wastheonethatdecidedwhichlogicalviewneededtobereturnedasaresponse.Thisis
simpletounderstandandsufficientforstraightforwardpageflows,butwhenweb
applicationsgetmoreandmorecomplexintermsofuserinterfaceflows,maintaininga
largeandcomplexpageflowbecomesanightmare.
Ifyouaregoingtodevelopsuchacomplexflow-basedapplication,thenSpringWeb
Flow(SWF)canbeagoodcompanion.SpringWebFlowallowsyoutodefineand
executeuserinterface(UI)flowswithinyourwebapplication.Withoutfurtherado,let’s
divestraightintoSpringWebFlowbydefiningsomepageflowsinourproject.
Itisnicethatwehaveimplementedtheshoppingcartinourpreviouschapter;however,it
isofnouseifwedonotprovideacheckoutfacilitytocompletetheprocessingofthe
orderandthenshiptheproductstotherightcustomers.Let’sdothatintwophases.Firstly,
let’screatetherequiredbackendservices,domainobjects,andrepositoryimplementation
inordertocompletetheorderprocessing(here,strictlynothingrelatedtoSpringWeb
Flowisinvolved;itisjustasupportivebackendservicethatcanbeusedlaterbytheweb
flowdefinitioninordertocompletethecheckoutprocess).Secondly,weneedtodefine
theactualSpringWebFlowdefinitionthatcanuseourbackendservicesinorderto
executetheflowdefinition.Here,wewillsettheconfigurationanddefinitionoftheactual
webflow.
Timeforaction–implementingtheorder-
processingservice
Wewillstartwithimplementingourorderprocessingbackendservicefirst.Weproceedas
follows:
1. CreateaclassnamedAddressunderthecom.packt.webstore.domainpackageinthe
sourcefoldersrc/main/javaandaddthefollowingcodeintoit.NotethatIhave
skippedthegetters,setters,equals,andhashcodemethodsinthefollowingsnippet.
Pleasedoaddthosewhenyoucreatethisclass:
packagecom.packt.webstore.domain;
importjava.io.Serializable;
publicclassAddressimplementsSerializable{
privatestaticfinallongserialVersionUID=-530086768384258062L;
privateStringdoorNo;
privateStringstreetName;
privateStringareaName;
privateStringstate;
privateStringcountry;
privateStringzipCode;
//addgettersandsettersforallthefieldshere.
//OverrideequalsandhashCodebasedonallthefields.
//thecodeforthesameisavailableinthecodebundlewhichcan
bedownloadedfromwww.packtpub.com/support
}
2. CreateanotherclassnamedCustomerunderthesamepackageandaddthefollowing
codeintoit:
packagecom.packt.webstore.domain;
importjava.io.Serializable;
publicclassCustomerimplementsSerializable{
privatestaticfinallongserialVersionUID=2284040482222162898L;
privateStringcustomerId;
privateStringname;
privateAddressbillingAddress;
privateStringphoneNumber;
publicCustomer(){
super();
this.billingAddress=newAddress();
}
publicCustomer(StringcustomerId,Stringname){
this();
this.customerId=customerId;
this.name=name;
}
//addgettersandsettersforallthefieldshere.
//OverrideequalsandhashCodebasedoncustomerIdfield.
//thecodeforthesameisavailableinthecodebundlewhichcan
bedownloadedfromwww.packtpub.com/support
}
3. CreateonemoredomainclassnamedShippingDetailunderthesamepackageand
addthefollowingcodeintoit:
packagecom.packt.webstore.domain;
importjava.io.Serializable;
importjava.util.Date;
importorg.springframework.format.annotation.DateTimeFormat;
publicclassShippingDetailimplementsSerializable{
privatestaticfinallongserialVersionUID=6350930334140807514L;
privateStringname;
@DateTimeFormat(pattern="dd/MM/yyyy")
privateDateshippingDate;
privateAddressshippingAddress;
publicShippingDetail(){
this.shippingAddress=newAddress();
}
//addgettersandsettersforallthefieldshere.
}
4. Similarly,createourfinaldomainclassnamedOrderunderthesamepackageand
addthefollowingcodeintoit:
packagecom.packt.webstore.domain;
importjava.io.Serializable;
publicclassOrderimplementsSerializable{
privatestaticfinallongserialVersionUID=-3560539622417210365L;

privateLongorderId;
privateCartcart;
privateCustomercustomer;
privateShippingDetailshippingDetail;

publicOrder(){
this.customer=newCustomer();
this.shippingDetail=newShippingDetail();
}
//addgettersandsettersforallthefieldshere.
//OverrideequalsandhashCodebasedonorderIdfield.
//thecodeforthesameisavailableinthecodebundlewhichcan
bedownloadedfromwww.packtpub.com/support
}
5. NowmaketheProduct,CartItem,andCartdomainclassesserializableby
implementingtheSerializableinterface(java.io.Serializable)forallofthese
classes;wealsoneedtoaddaserialVersionUIDfieldtoeachoftheearlier
mentionedclassesaswell.
6. Next,createaninterfacenamedOrderRepositoryunderthe
com.packt.webstore.domain.repositorypackageinthesourcefolder
src/main/java,andaddasinglemethoddeclarationtoitasfollows:
LongsaveOrder(Orderorder);
7. CreateanimplementationclasscalledInMemoryOrderRepositoryImplunderthe
com.packt.webstore.domain.repository.implpackageinthesourcefolder
src/main/javaandaddthefollowingcodeintoit:
packagecom.packt.webstore.domain.repository.impl;
importjava.util.HashMap;
importjava.util.Map;
importorg.springframework.stereotype.Repository;
importcom.packt.webstore.domain.Order;
importcom.packt.webstore.domain.repository.OrderRepository;
@Repository
publicclassInMemoryOrderRepositoryImplimplementsOrderRepository{
privateMap<Long,Order>listOfOrders;
privatelongnextOrderId;

publicInMemoryOrderRepositoryImpl(){
listOfOrders=newHashMap<Long,Order>();
nextOrderId=1000;
}
publicLongsaveOrder(Orderorder){
order.setOrderId(getNextOrderId());
listOfOrders.put(order.getOrderId(),order);
returnorder.getOrderId();
}
privatesynchronizedlonggetNextOrderId(){
returnnextOrderId++;
}
}
8. Now,opentheOrderServiceinterfacefromthecom.packt.webstore.service
packageinthesourcefoldersrc/main/javaandaddsinglemethoddeclarationstoit
asfollows:
packagecom.packt.webstore.domain.repository;
importcom.packt.webstore.domain.Order;
publicinterfaceOrderRepository{
LongsaveOrder(Orderorder);
}
}
9. Next,opentheimplementationclassOrderServiceImplfromthe
com.packt.webstore.service.implpackageinthesourcefoldersrc/main/java
andaddthefollowingtwoautowiredreferencestoit:
@Autowired
privateOrderRepositoryorderRepository;

@Autowired
privateCartServicecartService;
10. NowaddamethodimplementationforthesaveOrdermethodasfollowsinthe
OrderServiceImplclass:
publicLongsaveOrder(Orderorder){
LongorderId=orderRepository.saveOrder(order);
cartService.delete(order.getCart().getCartId());
returnorderId;
}
11. Next,createanexceptionclasscalledInvalidCartExceptionunderthe
com.packt.webstore.exceptionpackageinthesourcefoldersrc/main/javaand
addthefollowingcodeintoit:
packagecom.packt.webstore.exception;
publicclassInvalidCartExceptionextendsRuntimeException{
privatestaticfinallongserialVersionUID=-5192041563033358491L;
privateStringcartId;
publicInvalidCartException(StringcartId){
this.cartId=cartId;
}
publicStringgetCartId(){
returncartId;
}
}
12. Now,opentheCartServiceinterfacefromthecom.packt.webstore.service
packageinthesourcefoldersrc/main/javaandaddonemoremethoddeclarationto
itasfollows:
Cartvalidate(StringcartId);
13. Next,opentheimplementationclassCartServiceImplfromthepackage
com.packt.webstore.service.implinthesourcefoldersrc/main/javaandadda
methodimplementationforthevalidatemethodasfollows:
publicCartvalidate(StringcartId){
Cartcart=cartRepository.read(cartId);
if(cart==null||cart.getCartItems().size()==0){
thrownewInvalidCartException(cartId);
}

returncart;
}
Whatjusthappened?
WhatwehavedonesofarisfamiliartoyouIguess;wecreatedsomedomainclasses
(Address,Customer,ShippingDetail,andOrder)aswellasanOrderRepository
interfaceanditsimplementationclassInMemoryOrderRepositoryImpltostorethe
processedOrderdomainobjects.Finally,wealsocreatedthecorrespondingOrderService
interfaceanditsimplementationclass,namelyOrderServiceImpl.
Onthesurface,itlooksasusual,buttherearesomeminutedetailsthatneedtobe
explained.Ifyounotice,allthedomainclasseswecreatedfromsteps1to4havejust
implementedtheSerializableinterface;notonlythat,weevenimplementedthe
Serializableinterfaceforotherexistingdomainclassesaswell,suchasProduct,
CartItem,andCartinstep5.Thisisbecauselaterwewillusethesedomainobjectsin
SpringWebFlow,andSpringWebFlowwillstorethesedomainobjectsinasessionto
managethestatebetweenpageflows.Sessiondatacouldbesavedintoadiskor
transferredtoanotherwebserverduringclustering.So,whilebringingbackthesession
objectfromthedisk,SpringWebFlowwilldeserializethedomainobject(form-backing
bean)tomaintainthestateofthepage.That’swhyitisamusttoserializethedomain
object/formbackingbean.SpringWebFlowusesatermcalledSnapshottomention
thesestateswithinasession.
Theremainingstepsfromstep6to13areself-explanatory.Wecreatedthe
OrderRepositoryandOrderServiceinterfacesandtheircorresponding
InMemoryOrderRepositoryImplandOrderServiceImplimplementations.Thepurposeof
theseclassesistosavetheOrderdomainobject.ThesaveOrdermethodfrom
OrderServiceImpljustdeletesthecorrespondingCartobjectfromCartRepositoryafter
successfullysavingtheorderdomainobject.Now,wehavesuccessfullycreatedallthe
requiredbackendservicesanddomainobjectsinordertokickofftheconfigurationand
definitionofourSpringWebFlow.
Timeforaction–implementingthe
checkoutflow
WewillnowaddSpringWebFlowsupporttoourprojectanddefinethecheckoutflowfor
ourshoppingcart.Considerthefollowingsteps:
1. Openpom.xml;youwillfindpom.xmlundertherootdirectoryoftheproject.
2. Youwillbeabletoseesometabsatthebottomofthepom.xmlfile.Selectthe
DependenciestabandclickontheAddbuttonintheDependenciessection.
3. ASelectDependencywindowwillappear;enterGroupIdas
org.springframework.webflow,ArtifactIdasspring-webflow,Versionas
2.3.3.RELEASE,selectScopeascompile,andclickontheOKbuttonandsave
pom.xml.
4. Createadirectorystructure,flows/checkout/,underthedirectory
src/main/webapp/WEB-INF/andcreateanXMLfilecalledcheckout-flow.xml.
Then,addthefollowingcontentintoitandsaveit:
<?xmlversion="1.0"encoding="UTF-8"?>
<flowxmlns="http://www.springframework.org/schema/webflow"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/webflow
http://www.springframework.org/schema/webflow/spring-webflow.xsd">
<varname="order"class="com.packt.webstore.domain.Order"/>
<action-stateid="addCartToOrder">
<evaluate
expression="cartServiceImpl.validate(requestParameters.cartId)"
result="order.cart"/>
<transitionto="InvalidCartWarning"
on-exception="com.packt.webstore.exception.InvalidCartException"
/>
<transitionto="collectCustomerInfo"/>
</action-state>
<view-stateid="collectCustomerInfo"view="collectCustomerInfo.jsp"
model="order">
<transitionon="customerInfoCollected"to="collectShippingDetail"
/>
</view-state>
<view-stateid="collectShippingDetail"model="order">
<transitionon="shippingDetailCollected"to="orderConfirmation"/>
<transitionon="backToCollectCustomerInfo"to="collectCustomerInfo"
/>
</view-state>
<view-stateid="orderConfirmation">
<transitionon="orderConfirmed"to="processOrder"/>
<transitionon="backToCollectShippingDetail"
to="collectShippingDetail"/>
</view-state>

<action-stateid="processOrder">
<evaluateexpression="orderServiceImpl.saveOrder(order)"
result="order.orderId"/>
<transitionto="thankCustomer"/>
</action-state>

<view-stateid="InvalidCartWarning">
<transitionto="endState"/>
</view-state>

<view-stateid="thankCustomer"model="order">
<transitionto="endState"/>
</view-state>
<end-stateid="endState"/>
<end-stateid="cancelCheckout"view="checkOutCancelled.jsp"/>

<global-transitions>
<transitionon="cancel"to="endState"/>
</global-transitions>
</flow>
5. NowopenthewebapplicationcontextconfigurationfileDispatcherServlet-
context.xmlandaddthefollowingwebflownamespaceattributetothe<beans>tag
atthetop:
xmlns:webflow-config="http://www.springframework.org/schema/webflow-
config"
6. Appendthefollowingschemalocationentrytotheexistingxsi:schemaLocation
attributeofthe<beans>tag:
http://www.springframework.org/schema/webflow-config
http://www.springframework.org/schema/webflow-config/spring-webflow-
config-2.3.xsd
7. Nowaddthefollowingwebflowconfigurationtagstothewebapplicationcontext
configurationfile(DispatcherServlet-context.xml):
<webflow-config:flow-executorid="flowExecutor"flow-
registry="flowRegistry"/>
<webflow-config:flow-registryid="flowRegistry"base-path="/WEB-
INF/flows">
<webflow-config:flow-locationpath="/checkout/checkout-flow.xml"
id="checkout"/>
</webflow-config:flow-registry>
8. Finally,definethebeansforFlowHandlerMappingandFlowHandlerAdapterin
DispatcherServlet-context.xmlasfollowsandsavethefile:
<beanid="flowHandlerMapping"
class="org.springframework.webflow.mvc.servlet.FlowHandlerMapping">
<propertyname="flowRegistry"ref="flowRegistry"/>
</bean>
<beanid="flowHandlerAdapter"
class="org.springframework.webflow.mvc.servlet.FlowHandlerAdapter">
<propertyname="flowExecutor"ref="flowExecutor"/>
</bean>
Whatjusthappened?
Fromsteps1to3,wejustaddedtheSpringWebFlowdependencytoourprojectthrough
aMavenconfiguration.Itwilldownloadandconfigurealltherequiredjarsrelatedtoweb
flowinourproject.Instep4,wecreatedourfirstflowdefinitionfilecalledcheckout-
flow.xmlunderthedirectory/src/main/webapp/WEB-INF/flows/checkout/.
SpringWebFlowusestheflowdefinitionfileasabasistoexecutetheflow.Inorderto
understandwhathasbeenwritteninthisfile,weneedtogetaclearideaaboutsomeofthe
basicconceptsofSpringWebFlow.Wewilllearnaboutthoseconceptsalittlebitandthen
wewillcomebacktocheckout-flow.xmltounderstandit.
Understandingtheflowdefinition
Aflowdefinitioniscomposedofasetofstates.EachstatewillhaveauniqueIDinthe
flowdefinition.TherearesixtypesofstatesavailableinSpringWebFlow:
start-state:Eachflowmusthaveasinglestartstatethathelpsinthecreationofthe
initialstateoftheflow.Notethatifthestartstateisnotspecified,theveryfirst
definedstatewithintheflowdefinitionfilebecomesthestartstate.
action-state:Aflowcanhavemanyactionstates,andanactionstateexecutesa
particularaction.Anactionnormallyinvolvesinteractionwithbackendservices,
suchasexecutingsomemethodsinaSpring-managedbean;SpringWebFlowuses
SpringExpressionLanguagetointeractwithbackendservicebeans.
view-state:Aviewstatedefinesalogicalviewandmodeltointeractwiththeend
user.Awebflowcanhavemultipleviewstates.Iftheviewattributeisnotspecified,
thentheIDoftheviewstateactsasthelogicalviewname.
decision-state:Thedecisionstateisusedtobranchtheflow;basedonthetest
condition,itroutesthetransitiontothenextpossiblestate.
subflow-state:Asubflowisanindependentflowthatcanbereusedfrominside
anotherflow.Whenanapplicationentersasubflow,themainflowispauseduntilthe
concernedsubflowiscompleted.
end-state:Anendstatedenotestheendofaflow’sexecution.Awebflowcanhave
multipleendstates,andthroughtheviewattributeofend-state,wecanspecifya
viewthatwillberenderedwhentheendstateisreached.
Wehavejustlearnedthataflowdefinitioniscomposedofasetofstates,butinorderto
makeamovefromonestatetoanother,weneedtodefinetransitionsinthesestates.Each
stateinawebflow(exceptforthestartandendstates)definesanumberoftransitionsto
movefromonestatetoanother.Atransitioncanbetriggeredbyaneventthatissignaled
fromthestate.
Understandingthecheckoutflow
Okay!WejustgottheminimumrequiredintroductionforSpringWebFlowconcepts.
ThereareplentyofadvancedconceptsouttheretomasterinSpringWebFlow;wearenot
goingtolookatallofthosebecausethatitselfdeservesaseparatebook.Asofnow,itis
enoughtounderstandthecheckout-flow.xmlflowdefinitionfile.However,beforewedo
this,wewillhaveaquickoverviewofourcheckoutflow.Thefollowingdiagramwillgive
youtheoverallideaofthecheckoutflowthatwehavejustimplemented:
Ourcheckoutflowdiagramhasastartstateandanendstate;eachroundedrectangleinthe
diagramdefinesanactionstate,andeachdouble-line-borderedroundedrectangledefines
aviewstate.Similarly,eacharrowedlinedefinesatransition,andthenameassociated
withitdefinestheeventthatcausesthatparticulartransition.Thecheckout-flow.xmlfile
justcontainstheearliermentionedflowinanXMLrepresentation.
Ifyouopenthecheckout-flow.xmlfile,thefirsttagyouwillencounterwithinthe<flow>
tagisthe<var>tag:
<varname="order"class="com.packt.webstore.domain.Order"/>
The<var>tagcreatesavariableinaflow.Thisvariablewillbeavailabletoallthestates
inaflow,whichmeanswecanreferenceandusethisvariableinsideanystatewithinthe
flow.Inthejustmentioned<var>tag,wecreatedanewinstanceoftheOrderclassand
storeditinavariablecalledorder.
Thenextthingwedefinedwithinthecheckout-flow.xmlfilewasthe<action-state>
definition;asalreadylearned,actionstatesarenormallyusedtoinvokebackendservices.
Inthefollowing<action-state>definition,wewillinvokethevalidatemethodofthe
cartServiceImplobjectandstoretheresultintheorder.cartobject:
<action-stateid="addCartToOrder">
<evaluateexpression
="cartServiceImpl.validate(requestParameters.cartId)"
result="order.cart"/>
<transitionto="InvalidCartWarning"on-exception
="com.packt.webstore.exception.InvalidCartException"/>
<transitionto="collectCustomerInfo"/>
</action-state>
Asalreadydefined,theordervariableatthestartoftheflowwillbeavailableinevery
stateofthisflow.So,wehaveusedthatvariable(order.cart)inthe<evaluate>tagto
storetheresultoftheevaluatedexpression,namely
cartServiceImpl.validate(requestParameters.cartId).
ThevalidatemethodofcartServiceImplwilltrytoreadacartobjectbasedonthe
givencartId.Ifitfindsavalidcartobject,thenitwillreturnit;otherwise,itwillthrow
InvalidCartException.Insuchacase,wewillroutethetransitiontoanotherstatewhose
IDisInvalidCartWarning:
<transitionto="InvalidCartWarning"on-exception=
"com.packt.webstore.exception.InvalidCartException"/>
Ifsuchanexceptionisnotthrownfromtheexpressionevaluation,wewillnaturallytransit
fromtheaddCartToOrderstatetothecollectCustomerInfostate,asfollows:
<transitionto="collectCustomerInfo"/>
IfyounoticethecollectCustomerInfostate,itisnothingbutaviewstateincheckout-
flow.xml.Wedefinedtheviewthatneedstoberenderedviatheviewattributeandthe
modelthatneedstobeattachedviathemodelattribute,asfollows:
<view-stateid="collectCustomerInfo"view="collectCustomerInfo.jsp"
model="order">
<transitionon="customerInfoCollected"to="collectShippingDetail"/>
</view-state>
Uponreachingthisviewstate,SpringWebFlowwillrenderthecollectCustomerInfo
viewandwaitfortheusertointeract.Oncetheuserentersthecustomerinfodetailsand
pressesthesubmitbutton,itwillresumeitstransitiontothecollectShippingDetail
viewstate.Asalreadylearned,atransitioncanbetriggeredviaanevent,soherethe
transitiontothecollectShippingDetailstatewouldgettriggeredwhenthe
customerInfoCollectedeventistriggered.Buthowdoyoufirethisevent
(customerInfoCollected)fromtheview?Wewillseethislaterinthechapter.Consider
thefollowingcodesnippet:
<transitionon="customerInfoCollected"to="collectShippingDetail"/>
ThenextstatedefinedwithinthecheckoutflowiscollectShippingDetail.Again,thisis
alsoaviewstate,andithastwotransitionsbackandforth;oneistogobacktothe
collectCustomerInfostateandthenextistogoforwardtotheorderConfirmationstate,
asshownasfollows:
<view-stateid="collectShippingDetail"model="order">
<transitionon="shippingDetailCollected"to="orderConfirmation"/>
<transitionon="backToCollectCustomerInfo"to="collectCustomerInfo"/>
</view-state>
Noteherethatwehaven’tmentionedtheviewattributeinthecollectShippingDetail
state;inthiscase,SpringWebFlowwouldconsidertheIDoftheviewstateasitsview
name.
TheorderConfirmationstatedefinitiondoesn’tneedmuchexplanation;itismorelike
thecollectShippingDetailviewstatewherewefurnishalltheorder-relateddetailsand
thenasktheusertoconfirm.Uponconfirmation,wemovetothenextstate,thatis,
processOrder:
<view-stateid="orderConfirmation">
<transitionon="orderConfirmed"to="processOrder"/>
<transitionon="backToCollectShippingDetail"to="collectShippingDetail"
/>
</view-state>
Next,theprocessOrderstateisanactionstatethatinteractswiththeorderServiceImpl
objecttosavetheorderobject.Uponsuccessfullysavingtheorderobject,itstoresthe
orderIDintheflowvariable(order.orderId)andtransitsittothenextstate,whichis
thankCustomer:
<action-stateid="processOrder">
<evaluateexpression="orderServiceImpl.saveOrder(order)"
result="order.orderId"/>
<transitionto="thankCustomer"/>
</action-state>
ThethankCustomerstateisaviewstatethatsimplyshowsathankyoumessagewiththe
confirmedorderIDtotheenduserandtransitsittotheendstate,asfollows:
<view-stateid="thankCustomer"model="order">
<transitionto="endState"/>
</view-state>
Inourcheckoutflow,wehavetwoendstates:oneisthenormalendstatewheretheflow
executionarrivesnaturallyaftertheflowends,andtheotheroneistheendstatethatis
reachedwhentheuserpressesthecancelbuttoninanyoneoftheviews.Considerthe
followingcodesnippet:
<end-stateid="endState"/>
<end-stateid="cancelCheckout"view="checkOutCancelled.jsp"/>
NotethatinthecancelCheckoutendstate,wespecifiedthenameofthelandingpagevia
theviewattribute,andthetransitiontothecancelCheckoutendstatehappenedthrough
theglobal-transitionsconfiguration:
<global-transitions>
<transitionon="cancel"to="cancelCheckout"/>
</global-transitions>
Aglobaltransitionisforsharingsomecommontransitionsbetweenstates.Insteadof
repeatingthetransitiondefinitioneverytimewithinthestatedefinition,wecandefine
themwithinoneglobaltransitionsothatthattransitionwillbeavailableimplicitlyfor
everystateintheflow.Inourcase,theendusermaycancelthecheckoutprocessinany
state;thisiswhywedefinedthetransitiontothecancelCheckoutstateinglobal-
transitions.
Wehavetotallyunderstoodthecheckoutflowdefinition(checkout-flow.xml).Nowour
SpringMVCshouldreadthisfileduringthebootupofourapplicationsothatitcanbe
readytodispatchanyflow-relatedrequeststotheSpringWebFlowframework.Wewill
beabletodothisviasomewebflowconfigurationtagsinthewebapplicationcontext
(DispatcherServlet-context.xml)asmentionedinsteps5to8.
Insteps5and6,weaddedtherequiredwebflow-confignamespaceandschemalocation
inDispatcherServlet-context.xml.Instep7,wecreatedflow-executorandflow-
registry.Asthenameimplies,flow-executorexecutesaflowbasedonthegivenflow
definition.Theflow-executorconfigurationtaggetsitsflowdefinitionfromflow-
registry.Wecanconfigureasmanyflowdefinitionsaswewantinflow-registry.A
flow-registryconfigurationtagisacollectionofflowdefinitions.Whenauserentersa
flow,theflowexecutorcreatesandlaunchesanexclusiveflowinstanceforthatuserbased
ontheflowdefinition:
<webflow-config:flow-executorid="flowExecutor"flow-
registry="flowRegistry"/>
<webflow-config:flow-registryid="flowRegistry"base-path="/WEB-
INF/flows">
<webflow-config:flow-locationpath="/checkout/checkout-flow.xml"
id="checkout"/>
</webflow-config:flow-registry>
Intheprecedingwebflowconfiguration,wecreatedflow-registrywhosebase-pathis
/WEB-INF/flows,soweneedtoputallourflowdefinitionsunderthe/WEB-INF/flows
directoryinordertobepickedupbyflow-registry.That’swhy,instep4,wecreatedour
checkout-flow.xmlfileunderthedirectorysrc/main/webapp/WEB-
INF/flows/checkout/.Asalreadymentioned,flow-registrycanhavemanyflow
definitions,andeachflowdefinitionisidentifiedbyitsIDwithinflow-registry.Inour
case,weaddedasingleflowdefinitionwhoseIDischeckoutandwhoserelativelocation
is/checkout/checkout-flow.xml.Rememberthatthepathattributeofa<webflow-
config:flow-location>tagisrelativetothebase-pathattributeofthe<webflow-
config:flow-registry>tag.
Oneimportantthingtounderstandbeforewewindupthewebflowconfigurationisthat
theIDofaflowdefinitionformstherelativeURLtoinvoketheflow.Bythis,whatImean
isthatinordertoinvoketheflowofourcheckoutviaawebrequest,weneedtofireaGET
requesttotheURLhttp://localhost:8080/webstore/checkoutbecauseourflowIDis
checkout.Moreover,inourflowdefinition(checkout-flow.xml),wehaven’tconfigured
anystartstate,sothefirststatedefinition(theaddCartToOrderactionstate)willbecome
thestartstate;also,theaddCartToOrderactionstateexpectingcartIdshouldbepresent
intherequestparameteroftheinvokingURL,whichisshownasfollows:
<action-stateid="addCartToOrder">
<evaluateexpression=
"cartServiceImpl.validate(requestParameters.cartId)"result="order.cart"/>
<transitionto="InvalidCartWarning"on-
exception="com.packt.webstore.exception.InvalidCartException"/>
<transitionto="collectCustomerInfo"/>
</action-state>
So,theactualURLthatcaninvokethisflowwouldbesomethingsimilarto
http://localhost:8080/webstore/checkout?cartId=55AD1472D4EC,wherethepart
afterthequestionmark(cartId=55AD1472D4EC)isconsideredasarequestparameter.
ItisgoodthatwehavedefinedourcheckoutflowandconfigureditwithSpringWeb
Flow;however,weneedtodefinetwomorebeansinourwebapplicationcontext
(DispatcherServlet-context.xml)todispatchallflow-invokingrequeststoflow-
executor.Wedidthisinstep8:
<beanid="flowHandlerMapping"class=
"org.springframework.webflow.mvc.servlet.FlowHandlerMapping">
<propertyname="flowRegistry"ref="flowRegistry"/>
</bean>
<beanid="flowHandlerAdapter"class=
"org.springframework.webflow.mvc.servlet.FlowHandlerAdapter">
<propertyname="flowExecutor"ref="flowExecutor"/>
</bean>
TheflowHandlerMappingparametercreatesandconfiguresahandlermappingbasedon
theflowIDforeachdefinedflowfromflowRegistry.TheflowHandlerAdapteractsasa
bridgebetweenthedispatcherservletandSpringWebFlowinordertoexecutethe
instancesoftheflow.
Popquiz–webflow
Q1.Considerthefollowingwebflowregistryconfiguration;ithasasingleflowdefinition
file.HowwillyouformtheURLtoinvoketheflow?
<webflow-config:flow-registryid="flowRegistry"base-path="/WEB-
INF/flows">
<webflow-config:flow-locationpath="/customer/validate.xml"
id="validateCustomer"/>
</webflow-config:flow-registry>
1. http://localhost:8080/webstore/customer/validate
2. http://localhost:8080/webstore/validate
3. http://localhost:8080/webstore/validateCustomer
Q2.Considerthisflow-invokingURL:http://localhost:8080/webstore/validate?
customerId=C1234.Inaflowdefinitionfile,howwillyouretrievethecustomerIdHTTP
requestparameter?
1. <evaluateexpression="requestParameters.customerId"result=
"customerId"/>
2. <evaluateexpression="requestParameters(customerId)"result=
"customerId"/>
3. <evaluateexpression="requestParameters[customerId]"result=
"customerId"/>
Timeforaction–creatingviewsforevery
viewstate
Wehavedoneeverythingtorolloutourcheckoutflow,butonelastthingispending,that
is,creatingalltheviewsthatneedtobeusedintheviewstatesofourcheckoutflow.In
total,wehavesixviewstatesinourflowdefinition(collectCustomerInfo,
collectShippingDetail,orderConfirmation,InvalidCartWarning,thankCustomer,
andcancelCheckout),soweneedtocreatesixJSPfiles.Let’screateallofthem:
1. CreateaJSPviewfilecalledcollectCustomerInfo.jspunderthedirectory
src/main/webapp/WEB-INF/flows/checkout/,andaddthefollowingcodesnippet
intoitandsaveit.Inthefollowingcodesnippet,Ihaveskippedthe<input>tagsfor
someofthefieldsoftheCustomerdomainobject.Youcanfindthecompletecodefor
collectCustomerInfo.jspinthecodebundleofthisbook,whichcanbe
downloadedfromwww.packtpub.com/support.Considerthefollowingcodesnippet:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglibprefix="form"
uri="http://www.springframework.org/tags/form"%>
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
<html>
<head>
<metahttp-equiv="Content-Type"content="text/html;charset="utf-
8">
<linkrel="stylesheet"
href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<title>Customer</title>
</head>
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1>Customer</h1>
<p>Customerdetails</p>
</div>
</div>
</section>
<sectionclass="container">
<form:formmodelAttribute="order.customer"class="form-
horizontal">
<fieldset>
<legend>CustomerDetails</legend>
<divclass="form-group">
<labelclass="control-labelcol-lg-2col-lg-2"
for="customerId"/>CustomerId</label>
<divclass="col-lg-10">
<form:inputid="customerId"path="customerId"type="text"
class="form:input-large"/>
</div>
</div>
<!--Similarly,addinputtagsfortheremainingfieldsofthe
customerdomainobject.Ihaveskippedthosetagshere-->
<inputtype="hidden"name="_flowExecutionKey"
value="${flowExecutionKey}"/>
<divclass="form-group">
<divclass="col-lg-offset-2col-lg-10">
<inputtype="submit"id="btnAdd"class="btnbtn-primary"
value="Add"name="_eventId_customerInfoCollected"/>
<buttonid="btnCancel"class="btnbtn-default"
name="_eventId_cancel">Cancel</button>
</div>
</div>
</fieldset>
</form:form>
</section>
</body>
</html>
2. Similarly,createonemoreJSPviewfilecalledcollectShippingDetail.jspunder
thesamedirectory,andaddthefollowingcodesnippetintoitandsaveit.Inthe
followingcodesnippet,Ihaveskippedthe<input>tagsforsomeofthefieldsofthe
Address(shippingAddress)domainobject.Youcanfindthecompletecodefor
collectShippingDetail.jspinthecodebundleofthisbook,whichcanbe
downloadedfromwww.packtpub.com/support.Considerthefollowingcodesnippet:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglibprefix="form"
uri="http://www.springframework.org/tags/form"%>
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
<html>
<head>
<metahttp-equiv="Content-Type"content="text/html;charset="utf-
8">
<linkrel="stylesheet"
href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<title>Customer</title>
</head>
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1>Shipping</h1>
<p>Shippingdetails</p>
</div>
</div>
</section>
<sectionclass="container">
<form:formmodelAttribute="order.shippingDetail"class="form-
horizontal">
<fieldset>
<legend>ShippingDetails</legend>
<divclass="form-group">
<labelclass="control-labelcol-lg-2col-lg-2"for="name"
/>Name</label>
<divclass="col-lg-10">
<form:inputid="name"path="name"type="text"
class="form:input-large"/>
</div>
</div>
<divclass="form-group">
<labelclass="control-labelcol-lg-2col-lg-2"
for="shippingDate"/>shippingDate(dd/mm/yyyy)</label>
<divclass="col-lg-10">
<form:inputid="shippingDate"path="shippingDate"
type="text"class="form:input-large"/>
</div>
</div>
<divclass="form-group">
<labelclass="control-labelcol-lg-2"for="doorNo">Door
No</label>
<divclass="col-lg-10">
<form:inputid="doorNo"path="shippingAddress.doorNo"
type="text"
class="form:input-large"/>
</div>
</div>
<!--Similarly,addinputtagsfortheremainingfieldsofthe
shippingAddressdomainobject.Ihaveskippedthosetagshere-->
<inputtype="hidden"name="_flowExecutionKey"
value="${flowExecutionKey}"/>
<divclass="form-group">
<divclass="col-lg-offset-2col-lg-10">
<buttonid="back"class="btnbtn-default"
name="_eventId_backToCollectCustomerInfo">back</button>
<inputtype="submit"id="btnAdd"class="btnbtn-primary"
value="Add"name="_eventId_shippingDetailCollected"/>
<buttonid="btnCancel"class="btnbtn-default"
name="_eventId_cancel">Cancel</button>
</div>
</div>
</fieldset>
</form:form>
</section>
</body>
</html>
3. Also,createonemoreJSPviewfilecalledorderConfirmation.jsptoconfirmthe
orderfromtheuserunderthesamedirectory,andaddthefollowingcodesnippetinto
itandsaveit.Inthefollowingcodesnippet,Ihaveskippedthe<input>tagsforsome
ofthefieldsoftheOrderdomainobject.Youcanfindthecompletecodefor
orderConfirmation.jspinthecodebundleofthisbook,whichcanbedownloaded
fromwww.packtpub.com/support.Considerthefollowingcodesnippet:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglibprefix="form"
uri="http://www.springframework.org/tags/form"%>
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
<%@taglibprefix="fmt"uri="http://java.sun.com/jsp/jstl/fmt"%>
<html>
<head>
<metahttp-equiv="Content-Type"content="text/html;charset="utf-
8">
<linkrel="stylesheet"
href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<title>OrderConfirmation</title>
</head>
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1>Order</h1>
<p>OrderConfirmation</p>
</div>
</div>
</section>
<divclass="container">
<divclass="row">
<form:formmodelAttribute="order"class="form-horizontal">
<inputtype="hidden"name="_flowExecutionKey"
value="${flowExecutionKey}"/>
<divclass="wellcol-xs-10col-sm-10col-md-6col-xs-offset-1
col-sm-offset-1col-md-offset-3">
<divclass="text-center">
<h1>Receipt</h1>
</div>
<divclass="row">
<divclass="col-xs-6col-sm-6col-md-6">
<address>
<strong>ShippingAddress</strong><br>
${order.shippingDetail.name}<br>
<!--Similarly,furnisheveryfieldoftheorderobjectwithinanhtml
tableusingexpressionnotation"${}".Ihaveskippedthosetagshere-
->
<buttonid="back"class="btnbtn-default"
name="_eventId_backToCollectShippingDetail">back</button>
<buttontype="submit"class="btnbtn-success"
name="_eventId_orderConfirmed">
Confirm<spanclass="glyphiconglyphicon-chevron-
right"></span>
</button>
<buttonid="btnCancel"class="btnbtn-default"
name="_eventId_cancel">Cancel</button>
</div>
</div>
</form:form>
</div>
</div>
</body>
</html>
4. Next,weneedtocreateanotherJSPviewfilecalledInvalidCartWarning.jspto
showanerrormessageinthecaseofanemptycartcheckout;addthefollowingcode
snippettoInvalidCartWarning.jspandsaveit:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
<html>
<head>
<metahttp-equiv="Content-Type"content="text/html;charset="utf-
8">
<linkrel="stylesheet"
href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<title>Invalidcart</title>
</head>
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1class="alertalert-danger">InvalidCart</h1>
</div>
</div>
</section>
<section>
<divclass="container">
<p>
<ahref="<spring:urlvalue="/products"/>"class="btnbtn-
primary">
<spanclass="glyphicon-hand-leftglyphicon"></span>
products
</a>
</p>
</div>
</section>
</body>
</html>
5. Tothankthecustomerafterasuccessfulcheckoutflow,weneedtocreateonemore
JSPviewfilecalledthankCustomer.jspasfollows:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
<%@taglibprefix="fmt"uri="http://java.sun.com/jsp/jstl/fmt"%>
<html>
<head>
<metahttp-equiv="Content-Type"content="text/html;charset="utf-
8">
<linkrel="stylesheet"
href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<title>Invalidcart</title>
</head>
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1class="alertalert-danger">Thankyou</h1>
<p>Thanksfortheorder.yourorderwillbedeliveredtoyou
on
<fmt:formatDatetype="date"
value="${order.shippingDetail.shippingDate}"/>!</p>
<p>YourOrderNumberis${order.orderId}</p>
</div>
</div>
</section>
<section>
<divclass="container">
<p>
<ahref="<spring:urlvalue="/products"/>"class="btnbtn-
primary">
<spanclass="glyphicon-hand-leftglyphicon"></span>
products
</a>
</p>
</div>
</section>
</body>
</html>
6. Iftheusercancelsthecheckoutinanyoftheviews,weneedtoshowthecheckout
cancelledmessage;forthat,weneedtohaveaJSPfilecalled
checkOutCancelled.jspasfollows:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
<html>
<head>
<metahttp-equiv="Content-Type"content="text/html;charset="utf-
8">
<linkrel="stylesheet"
href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<title>Invalidcart</title>
</head>
<body>
<section>
<divclass="jumbotron">
<divclass="container">
<h1class="alertalert-danger">checkoutcancelled</h1>
<p>YourCheckoutprocesscancelled!youmaycontinue
shopping..</p>
</div>
</div>
</section>
<section>
<divclass="container">
<p>
<ahref="<spring:urlvalue="/products"/>"class="btnbtn-
primary">
<spanclass="glyphicon-hand-leftglyphicon"></span>
products
</a>
</p>
</div>

</section>
</body>
</html>
7. Asthelaststep,opencart.jspfromsrc\main\webapp\WEB-INF\views\andassign
the<spring:urlvalue="/checkout?cartId=${cartId}"/>valueforthehref
attributeofthecheckoutlinkasfollows:
<ahref="<spring:urlvalue="/checkout?cartId=${cartId}"/>"class="btn
btn-successpull-right"><span
class="glyphicon-shopping-cartglyphicon"></span>Checkout
</a>
8. Nowruntheapplicationandenterthehttp://localhost:8080/webstore/products
URL.Next,clickontheDetailsbuttonofanyoftheproductsandclickontheOrder
Nowbuttonontheproductdetailspagetoaddproductstotheshoppingcart.Nowgo
tothecartpagebyclickingontheViewCartbutton;youwillbeabletoseethe
Checkoutbuttononthatpage.ClickontheCheckoutbutton;youwillbeabletosee
awebpageasfollowsforcollectingcustomerinfo:
Customerdetailscollectionform
9. Afterfurnishingallthecustomerdetails,ifyouclickontheAddbutton,SpringWeb
Flowwilltakeyoutothenextviewstate,whichiscollectingtheshippingdetailsand
soonuptoconfirmingtheorder.Uponconfirmingtheorder,SpringWebFlowwill
showyouthethankyoumessageviewastheendstate.
Whatjusthappened?
Whatwehavedonefromstep1to6iskindofsimilar,thatis,creatingtheJSPviewfiles
foreachviewstate.Ifyouremember,wedefinedthemodelattributeforeachviewstatein
checkout-flow.xml.Considerthefollowingcodesnippet:
<view-stateid="collectCustomerInfo"view="collectCustomerInfo.jsp"
model="order">
<transitionon="customerInfoCollected"to="collectShippingDetail"/>
</view-state>
ThismodelobjectwillgetboundtotheviewviamodelAttributeofthe<form:form>tag
asfollows:
<form:formmodelAttribute="order.customer"class="form-horizontal">
<fieldset>
<legend>CustomerDetails</legend>
<divclass="form-group">
<labelclass="control-labelcol-lg-2col-lg-2"for="customerId"
/>CustomerId</label>
<divclass="col-lg-10">
<form:inputid="customerId"path="customerId"type="text"
class="form:input-large"/>
</div>
</div>
IntheprecedingsnippetofcollectCustomerInfo.jsp,youcannoticethatwebounded
the<form:input>tagwiththecustomerIdfieldofthecustomerobject,whichcomes
fromthemodelobject(order.customer).Similarly,weboundedtheshippingDetailand
orderobjectswithcollectShippingDetail.jspandorderConfirmation.jsp
respectively.
It’sgoodthatweboundedtheOrder,Customer,andShippingDetailobjectswiththe
views,butwhatwillhappenafterweclickonthesubmitbuttonineachview,orsaythe
thecancelorbackbuttons.Toknowtheanswer,weneedtoinvestigatethefollowingcode
snippetfromcollectCustomerInfo.jsp:
<inputtype="submit"id="btnAdd"class="btnbtn-primary"value="Add"
name="_eventId_customerInfoCollected"/>
Onthesurface,the<input>tagwejustmentionedactsasasubmitbutton,butthereal
differencecomesfromthenameattribute(name="_eventId_customerInfoCollected").
Wehaveassignedthevalue_eventId_customerInfoCollectedtothenameattributeof
the<input>tagwithapurpose.ThepurposeistoinstructSpringWebFlowtoraisean
eventoncethisformissubmitted.Whensubmittingthisform,SpringWebFlowwillraise
aneventbasedonthenameattribute.Sincewehaveassignedavaluewiththe_eventId_
prefix(_eventId_customerInfoCollected),SpringWebFlowcouldrecognizeitasan
eventnameandraiseaneventwiththenamecustomerInfoCollected.
Asalreadylearned,transitionfromonestatetoanotherhappenswiththehelpofevents.
So,uponsubmittingthecollectCustomerInfoform,SpringWebFlowwilltakeustothe
nextviewstate,thatis,collectShippingDetail:
<view-stateid="collectCustomerInfo"view="collectCustomerInfo.jsp"
model="order">
<transitionon="customerInfoCollected"to="collectShippingDetail"/>
</view-state>
Similarly,wecanraiseeventswhileclickingonthecancelorbackbuttons;seethe
followingcodesnippetfromcollectShippingDetail.jsp:
<buttonid="back"class="btnbtn-default"
name="_eventId_backToCollectCustomerInfo">back</button>
<buttonid="btnCancel"class="btnbtn-default"
name="_eventId_cancel">Cancel</button>
Okay!SoweunderstandhowtoraiseSpringWebFloweventsfromtheviewtodirectthe
transitionfromoneviewstatetoanother.However,weneedtounderstandonemore
importantconceptregardingtheSpringWebFlowexecution,thatis,eachflowexecution
isidentifiedbytheflowexecutionkeyatruntime.Duringtheflowexecution,whenaview
stateisentered,theflowexecutionpausesandwaitsfortheusertoperformanaction
(suchasenteringsomedataintheform).Whentheusersubmitstheformorchoosesto
cancelit,theflowexecutionkeyisalsosentalongwiththeformdatainordertoresume
theflowwhereitleftoff.Thisisdonewiththehelpofthehidden<input>tagasfollows:
<inputtype="hidden"name="_flowExecutionKey"value="${flowExecutionKey}"/>
Ifyoulookcarefully,wehavetheearliermentionedtagineveryflow-relatedviewfile
suchascollectCustomerInfo.jsp,collectShippingDetail.jsp,andsoon.SpringWeb
Flowwillstoreauniqueflowexecutionkeyunderthemodelattributename
flowExecutionKeyineveryflow-relatedview;weneedtostorethisvalueintheformofa
variablecalled_flowExecutionKeyinordertogetidentifiedbySpringWebFlow.
Sothat’sallaboutviewfilesthatareassociatedwiththedefinitionofourcheckoutflow.
However,weneedtoinvoketheflowuponclickingthecheckoutbuttonfromthecart
page.Aswehavealreadylearnedhowtoinvokeourcheckoutflow,weneedtofireaweb
requestwiththecartIDasarequestparameter.Instep7,wechangedthehrefattributeof
thecheckoutlinkasfollowstoformarequestURLthatissomethingsimilarto
http://localhost:8080/webstore/checkout?cartId=55AD1472D4EC.
So,nowifyouclickonthecheckoutbuttonafterselectingsomeproductsintothe
shoppingcart,youwillbeabletoinitiatethecheckoutflow.Thefollowingistheorder
confirmationpagethatwillappearastheoutcomeofreachingtheorderConfirmation
state:
Orderconfirmationpage
Haveagohero–addingadecisionstate
Althoughwehavefinishedwithourcheckoutflow,thereisstillsomeroomtoimprovethe
flow.Everytimethecheckoutflowstarts,itcollectsthecustomer’sdetails.Whatifa
returningcustomerplacesanorder?Probably,he/shemaynotliketoprovidecustomer
detailsrepeatedlyeverytime.However,youcanautofilldetails,therebypickingup
customerdetailsfromexistingrecords.Herearesomeoftheimprovementsyoucan
introducetoavoidcollectingcustomerdetailsinthecaseofregularcustomers:
Createacustomerrepositoryandservicelayertostore,retrieve,andfindcustomer
objects.Probably,youcanhavemethodssuchasthefollowinginyour
CustomerRepositoyandCustomerServiceinterfacesandintheircorresponding
implementationclasses:
publicvoidsaveCustomer(Customercustomer)
publicCustomergetCustomer(StringcustomerId)
publicBooleanisCustomerExist(StringcustomerId)
Defineaviewstateincheckout-flow.xmltocollectthecustomerID.Don’tforgetto
createthecorrespondingJSPviewfiletocollectthecustomerID.
Defineadecisionstateincheckout-flow.xmltocheckwhetheracustomerexistsin
CustomerRepositoythroughCustomerService.BasedontheretuningBoolean
value,directthetransitiontocollectthecustomerdetailsviewstateorprefillthe
order.customerobjectfromCustomerRepositoy.Thefollowingisasample
decisionstate:
<decision-stateid="checkCustomerExist">
<iftest="customerServiceImpl.isCustomerExist(order.customer.
customerId)"
then="collectShippingDetail"
else="collectCustomerInfo"/>
</decision-state>
Aftercollectingcustomerdetails,don’tforgettostoretheinformationin
CustomerRepositoythroughanactionstate.Similarly,filltheorder.customer
objectafterthedecisionstate.
EnhancingreusabilitythroughApache
Tiles
Inthepast,wedevelopedaseriesofwebpages(views),suchasapagetoshowproducts,
anotherpagetoaddproducts,andsoon,aspartofourwebstoreapplication;thoughevery
viewservesadifferentpurpose,allofthemshareacommonvisualpattern,forexample,
eachpagehasaheader,contentarea,andsoon.Wehavehardcodedandrepeatedthose
commonelementsineveryJSPviewpage.Thisisnotagoodideabecauseinfuture,ifwe
wanttochangethelookandfeelofanyofthesecommonelements,wewillhaveto
changeeverypageinordertomaintainaconsistentlookandfeelacrossallthewebpages.
Toaddressthisproblem,modernwebapplicationsusetemplatemechanisms;Apache
Tilesisonesuchtemplatecompositionframework.Tilesallowdeveloperstodefine
reusablepagefragments(tiles)thatcanbeassembledintoacompletewebpageatruntime.
Thesefragmentscanhaveparameterstoallowdynamiccontent.Thisincreasesthe
reusabilityoftemplatesandreducescodeduplication.
Timeforaction–creatingviewsforevery
viewstate
Enoughofintroduction;let’sdiveintoApacheTilesbydefiningacommonlayoutforour
webapplicationandletthepagesextendthelayout:
1. Openpom.xml;youwillfindpom.xmlundertheprojectrootdirectory.
2. Youwillbeabletoseesomebottomtabsunderpom.xml;selecttheDependenciestab
andclickontheAddbuttonoftheDependenciessection.
3. ASelectDependencywindowwillappear;enterGroupIdasorg.apache.tiles,
ArtifactIdastiles-extras,andVersionas3.0.3.Then,selectScopeascompile,
clickontheOKbutton,andsavepom.xml.
4. Similarly,addonemoredependencywithGroupIdasorg.slf4j,ArtifactIdas
slf4j-api,andVersionas1.7.5.Then,selectScopeascompile,clickontheOK
button,andsavepom.xml.
5. Nowcreateadirectorystructure,tiles/definitions/,underthedirectory
src/main/webapp/WEB-INF/;then,createanXMLfilecalledtile-definition.xml,
addthefollowingcontentintoit,andsaveit.Inthefollowingcodesnippet,Ihave
skippedthe<definition>tagsforsomeofthefieldsoflogicalviewnames.Youcan
findthecompletecodefordefinition.xmlinthecodebundleofthisbook,which
canbedownloadedfromwww.packtpub.com/support:
<?xmlversion="1.0"encoding="UTF-8"?>
<!DOCTYPEtiles-definitionsPUBLIC"-//ApacheSoftwareFoundation//DTD
TilesConfiguration3.0//EN"
"http://tiles.apache.org/dtds/tiles-config_3_0.dtd">
<tiles-definitions>

<definitionname="baseLayout"template="/WEB-
INF/tiles/template/baseLayout.jsp">
<put-attributename="title"value="SampleTitle"/>
<put-attributename="heading"value=""/>
<put-attributename="tagline"value=""/>
<put-attributename="navigation"value="/WEB-
INF/tiles/template/navigation.jsp"/>
<put-attributename="content"value=""/>
<put-attributename="footer"value="/WEB-
INF/tiles/template/footer.jsp"/>
</definition>

<definitionname="welcome"extends="baseLayout">
<put-attributename="title"value="Products"/>
<put-attributename="heading"value="Products"/>
<put-attributename="tagline"value="AvailableProducts"/>
<put-attributename="content"value="/WEB-INF/views/products.jsp"
/>
</definition>

<definitionname="products"extends="baseLayout">
<put-attributename="title"value="Products"/>
<put-attributename="heading"value="Products"/>
<put-attributename="tagline"value="AvailableProducts"/>
<put-attributename="content"value="/WEB-INF/views/products.jsp"
/>
</definition>

<definitionname="product"extends="baseLayout">
<put-attributename="title"value="Product"/>
<put-attributename="heading"value="Products"/>
<put-attributename="tagline"value="Product"/>
<put-attributename="content"value="/WEB-INF/views/product.jsp"/>
</definition>


<!—similarly,adddefinitiontagsforeverylogicalviewname.Ihave
skippedthishere,butyoucanfindthefulldefinitionfileinthe
codebundleofthisbook.-->
</tiles-definitions>
6. Nowcreateadirectorycalledtemplateunderthedirectorysrc/main/webapp/WEB-
INF/tiles/;then,createaJSPfilecalledbaseLayout.jsp,addthefollowingcontent
intoit,andsaveit:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
<%@taglibprefix="tiles"uri="http://tiles.apache.org/tags-tiles"%>
<!DOCTYPEhtml>
<htmllang="en">
<head>
<metacharset="utf-8">
<metahttp-equiv="X-UA-Compatible"content="IE=edge">
<metaname="viewport"content="width=device-width,initial-
scale=1.0">
<title><tiles:insertAttributename="title"/></title>
<linkhref="http://getbootstrap.com/dist/css/bootstrap.css"
rel="stylesheet">
<link
href="http://getbootstrap.com/examples/jumbotron/jumbotron.css"
rel="stylesheet">
</head>
<body>
<divclass="container">
<divclass="header">
<ulclass="navnav-pillspull-right">
<tiles:insertAttributename="navigation"/>
</ul>
<h3class="text-muted">WebStore</h3>
</div>
<divclass="jumbotron">
<h1>
<tiles:insertAttributename="heading"/>
</h1>
<p>
<tiles:insertAttributename="tagline"/>
</p>
</div>
<divclass="row">
<tiles:insertAttributename="content"/>
</div>
<divclass="footer">
<tiles:insertAttributename="footer"/>
</div>
</div>
</body>
</html>
7. Underthesamedirectory(template),createanothertemplateJSPfilecalled
navigation.jspandaddthefollowingcontentintoit:
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
<li><ahref="<spring:urlvalue="/products"/>">Home</a></li>
<li><ahref="<spring:URLvalue="/products/"/>">Products</a></li>
<li><ahref="<spring:urlvalue="/products/add"/>">AddProduct</a></li>
<li><ahref="<spring:urlvalue="/cart/"/>">Cart</a></li>
8. Similarly,createonelasttemplateJSPfilecalledfooter.jspandaddthefollowing
contenttoit:
<p>&copy;Company2014</p>
9. Wehavecreatedthecommonbaselayouttemplateandthetiledefinitionforallour
pages.NowweneedtoremovethecommonpageelementsfromallourJSPview
files.Forexample,ifyouremovethejumbotronsectionfromproducts.jspand
keeponlythecontainersection,itwouldlooklikethefollowing.Notethatyou
shouldnotremovethetaglibreferencesandlinkreferencestoJavaScriptfiles:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
<sectionclass="container">
<divclass="row">
<c:forEachvar="product"items="${products}">
<divclass="col-sm-6col-md-3"style="padding-bottom:15px">
<divclass="thumbnail">
<img
src="<c:url
value="/resource/images/${product.productId}.png"></c:url>"
alt="image"style="width:100%"/>
<divclass="caption">
<h3>${product.name}</h3>
<p>${product.description}</p>
<p>${product.unitPrice}USD</p>
<p>Available${product.unitsInStock}unitsinstock</p>
<p>
<a
href="<spring:urlvalue="/products/product?
id=${product.productId}"/>"
class="btnbtn-primary"><span
class="glyphicon-info-signglyphicon"/></span>Details
</a>
</p>
</div>
</div>
</div>
</c:forEach>
</div>
</section>
10. Similarly,removethejumbotronsectionfromeveryJSPviewfilethatisunderthe
/src/main/webapp/WEB-INF/viewsdirectory;donotremovethetaglibreferences
andlinkreferencestoJavaScriptfiles;forexample,incart.jsp,youshouldretain
thefollowinglines:
<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglibprefix="spring"uri="http://www.springframework.org/tags"%>
<script
src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.1/angular.min.
js"></script>
<scriptsrc="/webstore/resource/js/controllers.js"></script>
11. Finally,forTilesView,addaUrlBasedViewResolverbeantoourwebapplication
contextconfigurationfile(DispatcherServlet-context.xml),asfollows:
<beanid="tilesViewResolver"
class="org.springframework.web.servlet.view.UrlBasedViewResolver">
<propertyname="viewClass"
value="org.springframework.web.servlet.view.tiles3.TilesView"/>
<propertyname="order"value="-2"/>
</bean>
12. Inordertolocatethetiledefinitionfile,weneedtoaddabeandefinitionfor
TilesConfigurerinDispatcherServlet-context.xml,asfollows:
<beanid="tilesConfigurer"
class="org.springframework.web.servlet.view.tiles3.TilesConfigurer">
<propertyname="definitions">
<list>
<value>/WEB-INF/tiles/definitions/tile-definition.xml</value>
</list>
</property>
</bean>
13. NowruntheapplicationandentertheURL
http://localhost:8080/webstore/products;youwillbeabletoseeourregular
productaddpagewithanextranavigationbaratthetopandfooteratthebottom.You
cannavigatetoaddtheproductspagebyclickingontheAddProductlink.
ProductspagewithApacheTilesview
Whatjusthappened?
ToworkwithApacheTiles,weneedjarsrelatedtoApacheTiles;fromsteps1to4,we
addedthosejarsviaMavendependencies.Step5isveryimportantbecausewecreatedour
tilesdefinitionfile(tile-definition.xml)inthisstep.Understandingthetiledefinition
fileiscrucialfordevelopingapplicationsbasedonApacheTiles,sowewilltryto
understandourtiledefinitionfile(tile-definition.xml).
Atile’sdefinitionfileisacollectionofdefinitions,andeachdefinitioncanbeassociated
withatemplateviathetemplateattributeforthelayout;refertothefollowingcodeto
knowhowtodothis:
<definitionname="baseLayout"template="/WEB-
INF/tiles/template/baseLayout.jsp">
<put-attributename="title"value="SampleTitle"/>
<put-attributename="heading"value="SampleHeader"/>
<put-attributename="tagline"value="SampleTagline"/>
<put-attributename="navigation"value="/WEB-
INF/tiles/template/navigation.jsp"/>
<put-attributename="content"value=""/>
<put-attributename="footer"value="/WEB-INF/tiles/template/footer.jsp"
/>
</definition>
Withineachdefinition,wecandefinemanyattributes.Theseattributescanbeasimple
textvalueorafull-blownmarkupfile.Theseattributeswouldbeavailableinthetemplate
fileviathe<tiles:insertAttribute>tag.Forexample,ifyouopenthebaselayout
template(baseLayout.jsp),youwillnoticethefollowingsnippetunderthejumbotron
<div>tag:
<h1>
<tiles:insertAttributename="heading"/>
</h1>
<p>
<tiles:insertAttributename="tagline"/>
</p>
So,atruntime,ApacheTileswillreplacethe<tiles:insertAttributename="heading"
/>tagwiththevalueSampleHeader;similarly,the<tiles:insertAttribute
name="tagline"/>tagwillalsobereplacedwiththeSampleTaglinevalue.
So,baseLayoutisassociatedwiththetemplate/WEB-
INF/tiles/template/baseLayout.jsp,andwecaninsertthedefinedattributessuchas
tile,heading,andtaglineinthetemplateusingthe<tiles:insertAttribute>tag.
ApacheTilesallowsustoextendadefinitionjustlikehowweextendaJavaclasssothat
thedefinedattributeswillbeavailableforthederiveddefinition,andwecanevenoverride
theseattributevaluesifwewant.Forexample,lookatthefollowingdefinitionfromtile-
definition.xml:
<definitionname="products"extends="baseLayout">
<put-attributename="title"value="Products"/>
<put-attributename="heading"value="Products"/>
<put-attributename="tagline"value="AvailableProducts"/>
<put-attributename="content"value="/WEB-INF/views/products.jsp"/>
</definition>
ThementioneddefinitionisanextensionofthebaseLayoutdefinition.Wehaveonly
overriddenthetitle,heading,tagline,andcontentattributes,andsincewehavenot
definedanytemplateforthisdefinition,itusesthesametemplatethatweconfiguredfor
thebaseLayoutdefinition.
Similarly,wehavedefinedthetiledefinitionforeverypossiblelogicalviewnamethatcan
bereturnedfromourcontrollers.Notethateachdefinitionname(exceptthebaseLayout
definition)isalogicalviewname.
Fromsteps6to8,wecreatedthetemplatesthatcanbeusedinthetiledefinition;firstwe
createdthebaselayouttemplate(baseLayout.jsp),thenthenavigationtemplate
(navigation.jsp),andfinallythefootertemplate(footer.jsp).
Steps9and10explainedhowtoremovetheexistingredundantcontent,suchasthe
jumbotron<div>tag,fromeveryJSPviewpage.Notethatyouhavetobecarefulwhile
doingthings;don’taccidentlyremovethetaglibreferencesandlinkreferencesto
JavaScriptfiles.
InStep11,wedefinedUrlBasedViewResolverforTilesView
(org.springframework.web.servlet.view.tiles3.TilesView)inordertoresolve
logicalviewnamesintothetile’sview.Finally,instep12,weconfigured
TilesConfigurer
(org.springframework.web.servlet.view.tiles3.TilesConfigurer)tolocatethetile’s
definitionfilesbytheApacheTilesframework.
That’sit!IfyouruntheapplicationandentertheURL
http://localhost:8080/webstore/products,youwillbeabletoseeourregular
productspagewithanextranavigationbaratthetopandfooteratthebottomas
mentionedinstep13.YoucannavigatetoaddtheproductspagebyclickingontheAdd
Productlink.Previously,everytimealogicalviewnamewasreturnedbythecontroller
method,theInternalResourceViewResolvercameintoactionandfoundthe
correspondingjspviewforthegivenlogicalviewname.Now,foreverylogicalview
name,UrlBasedViewResolverwillcomeintoactionandcomposethecorrespondingview
basedonthetemplate’sdefinition.
Popquiz–ApacheTiles
Q1.WhichofthefollowingstatementsaretrueaccordingtoApacheTiles?
1. Alogicalviewnamereturnedbythecontrollermustbeequaltothe<definition>
tagname
2. The<tiles:insertAttribute>tagactsasaplaceholderinthetemplate
3. A<definition>tagcanextendanother<definition>tag
Summary
SpringWebFlowandApacheTilesaretwoseparateframeworks.Weonlysawthe
minimumrequiredconceptstogetaquickoverviewoftheseframeworksinthischapter.
Inthebeginning,welearnedsomeofthebasicconceptsoftheSpringWebFlow
frameworkandthencreatedthecheckoutflowforourwebstoreapplication.Inthesecond
partofthischapter,wesawhowtouseandleveragetheApacheTilesframeworkinorder
tobringmaximumreusabilityinviewfilesandmaintainaconsistentlookandfeel
throughoutallthewebpagesofourapplication.
Inthenextchapter,wewillseehowtotestourwebapplicationusingvariousAPIs
providedbySpringMVC.
Chapter10.TestingYourApplication
Forawebapplicationdeveloper,testingthewebapplicationsisalwaysachallenging
task,becausegettingareal-timetestenvironmentforwebapplicationsrequiresalotof
effort.ThankstotheSpringMVCTestframework,testingSpringMVCapplicationsis
simplified.
Butwhydoweneedtoconsiderputtingineffortstotestourapplication?Writinggood
testcasesforourapplicationiskindoflikebuyinginsuranceforyourapplication.
Althoughitdoesnotaddanyfunctionalvaluestoyourapplication,itwilldefinitelysave
yourtimeandeffortbydetectingoffunctionalityfailuresearly.Considerthatyour
applicationisgrowingbiggerandbiggerintermsoffunctionality;youneedsome
mechanismtoensurethatexistingfunctionalitiesarenotdisturbedduetotheintroduction
ofnewfunctionalities.
Testingframeworksprovideyouwiththiskindofmechanismtoensurethatyour
applicationbehaviorisnotalteredduetorefactoringortheadditionofnewcode.Italso
ensuresthattheexistingfunctionalityworksasexpected.
Inthischapter,wearegoingtoseethefollowingtopics:
Testingthedomainobjectandvalidator
Testingcontrollers
TestingRESTfulwebservices
Unittesting
Insoftwaredevelopment,unittestingisasoftwaretestingmethodinwhichthesmallest
testablepartsofsourcecode,calledunits,areindividuallyandindependentlytestedto
determinewhethertheybehaveexactlyasweexpect.Tounittestoursourcecode,allwe
needisatestprogramthatcanrunabitofoursourcecode(unit),providesomeinputto
eachunit,andchecktheresultsfortheexpectedoutput.Mostunittestsarewrittenusing
somesortoftestframeworksetoflibrarycode,designedtomakewritingandrunning
testseasier.OnesuchframeworkiscalledJUnit.ItisaunittestingframeworkfortheJava
programminglanguage.
Timeforaction–unit-testingdomain
objects
Let’sseehowtotestoneofourdomainobjectusingtheJUnitframeworktoensureit
functionsasexpected.Inanearlierchapter,wecreatedadomainobjecttorepresentan
iteminashoppingcart,calledCartItem.TheCartItemclasshasamethodcalled
getTotalPricetoreturnthetotalpriceofthatparticularcartitembasedontheproduct
andnumberofitemsitrepresents.Let’stestwhetherthegetTotalPricemethodbehaves
properly.Followthesesteps:
1. Openpom.xmlandyouwillfindpom.xmlundertherootdirectoryoftheprojectitself.
2. Youwillseesometabsatthebottomofthepom.xmlfile.SelecttheDependencies
tabandclickontheAddbuttonoftheDependenciessection.
3. ASelectDependencywindowwillappear;enterGroupIdasjunit,ArtifactIdas
junit,andVersionas4.11;thenselecttestasScope,clickontheOKbutton,and
savepom.xml.
4. NowcreateaclasscalledCartItemTestunderthepackage
com.packt.webstore.domaininthesourcefolder,src/test/java.Addthe
followingcodeintoitandsavethefile:
packagecom.packt.webstore.domain;
importjava.math.BigDecimal;
importorg.junit.Assert;
importorg.junit.Before;
importorg.junit.Test;
publicclassCartItemTest{

privateCartItemcartItem;
@Before
publicvoidsetup(){
cartItem=newCartItem();
}

@Test
publicvoid
cartItem_total_price_should_be_eaual_to_product_unit_price_in_case_of_s
ingle_quantity(){
//Arrange
Productiphone=newProduct("P1234","iPhone5s",new
BigDecimal(500));
cartItem.setProduct(iphone);

//Act
BigDecimaltotalPrice=cartItem.getTotalPrice();

//Assert
Assert.assertEquals(iphone.getUnitPrice(),totalPrice);
}
}
5. Nowright-clickonCartItemTest.javaandgotoRunAs|JUnitTest.Youwillsee
afailingtestcaseintheJUnitwindow,asshowninthefollowingscreenshot:
JUnitfailingtestcaseinCartItemTest
6. Tomakethetestcasepass,assignthevalue1tothequantityfieldofCartItemin
thezeroargumentconstructoroftheCartItemclass(asfollows)andsavethefile:
publicCartItem(){
this.quantity=1;
}
7. Now,right-clickagainonCartItemTest.javaandgotoRunAs|JUnitTest.You
willseethatthetestcasehaspassedintheJUnitwindow,asshowninthefollowing
screenshot:
JUnitpassedtestcaseinCartItemTest
Whatjusthappened?
AsIalreadymentioned,thegetTotalPricemethodoftheCartItemclassisdesignedto
returnthecorrecttotalpricebasedontheproductandthenumberofproductsitrepresents.
Buttoensureitsproperbehavior,wehavewrittenatestprogramcalledCartItemTest
underthecom.packt.webstore.domainpackageinthesourcefolder,src/test/java,as
mentionedinstep4.
InCartItemTest,weusedsomeoftheJUnitframeworkAPIs,suchasthe@Testand
@Beforeannotations.So,beforewecanusetheseannotationsinourCartItemTestclass,
weneedtoaddaJUnitjarasdependencyinourproject.That’swhatwedidinsteps1
through3.
Now,let’sgettoknowtheCartItemTestclassthoroughly.Theimportantmethodinthe
CartItemTestclassistheonethatisannotatedwith@Test,called
cartItem_total_price_should_be_eaual_to_product_unit_price_in_case_of_single_quantity
The@Testannotation(org.junit.Test)marksaparticularmethodasatestmethod.This
issothattheJUnitframeworkcantreatthatmethodasatestmethodandexecuteitwhen
wegotoRunAs|JUnitTest.Considerthefollowingcodesnippet:
@Test
publicvoid
cartItem_total_price_should_be_eaual_to_product_unit_price_in_case_of_singl
e_quantity(){
//Arrange
Productiphone=newProduct("P1234","iPhone5s",newBigDecimal(500));
cartItem.setProduct(iphone);

//Act
BigDecimaltotalPrice=cartItem.getTotalPrice();

//Assert
Assert.assertEquals(iphone.getUnitPrice(),totalPrice);
}
Ifyounotice,theprecedingmethodhasbeendividedintothreelogicalpartscalled
Arrange,Act,andAssert:
Arrange:Thissectionarrangesallthenecessarypreconditionsandinputstoperform
atest
Act:Thissectionactsontheobjectormethodundertest
Assert:Thissectionassertsthattheexpectedresultshaveoccurred
IntheArrangepart,wejustinstantiatedaproductdomainobject(iphone)withaunit
pricevalueof500andaddedthatproductobjecttothecartItemobjectbycalling
cartItem.setProduct(iphone);.WethenaddedasingleproducttocartItem.We
haven’talteredthequantityaspectofthecartItemobject.So,ifwecallthe
getTotalPricemethodofcartItem.Wemustget500(inBigDecimal),becausetheunit
priceofthedomainobject(iphone)wehaveaddedincartItemis500.
IntheActpart,wejustcalledthemethodundertest,whichisthegetTotalPricemethod
ofthecartItemobject,andstoredtheresultinaBigDecimalvariablecalledtotalPrice.
Later,intheAssertpart,weusedtheJUnitAPI(Assert.assertEquals)toassertthe
equalitybetweentheunitPricevalueoftheproductdomainobjectandthecalculated
totalPriceofcartItem.Havealookatthefollowingcode:
Assert.assertEquals(iphone.getUnitPrice(),totalPrice);
ThetotalPriceparameterofcartItemmustbeequaltotheunitPricevalueofthe
productdomainobjectwehaveaddedtocartItem.Thisisbecauseweaddedthesingle-
productdomainobjectwhoseunitPriceandtotalPricevalueneedtobethesame.
WhenwerunCartItemTestasmentionedinstep5,theJUnitframeworktriestoexecute
allthemethodsannotatedwith@TestintheCartItemTestclass.So,basedonthe
assertions’results,atestcasemayfailorpass.Inourcase,ourtestcasefailed.Youcan
seethatthefailuretraceshowsanerrormessagethatsaysexpected<500>butwas:<0>
inthescreenshotimmediatelyafterstep5.Thisisbecauseitdidn’tupdatethequantity
fieldofthecartItemobjectwhenweaddedaproductdomainobjecttocartIteminthe
Arrangepart.Itisabug.Tofixthisbug,wedefaultthequantityfieldvalueto1
wheneverweinstantiatecartItem,usingthezeroargumentconstructorasmentionedin
thestep6.Now,ifyourunthetestcaseagain,itpassesasexpected.
Haveagohero–addingtestsforcart
ItisgoodthatwehavetestedandverifiedthegetTotalPricemethodoftheCartItem
class.YoucansimilarlywriteatestclassfortheCartdomainobjectclass.IntheCart
domainobjectclass,thereisamethodtogetthegrandtotal(getGrandTotal)andwrite
varioustestcasestocheckwhetherthegetGrandTotalmethodworksasexpected.
IntegrationtestingwiththeSpringTest
Contextframework
Whenindividualprogramunitsarecombinedandtestedasagroup,itisknownas
integrationtesting.TheSpringTestContextframeworkgivesfirstclasssupportforthe
integrationtestingofSpring-basedapplications.WehavedefinedlotsofSpring-managed
beansinourwebapplicationcontext(DispatcherServlet-context.xml),suchas
services,repositories,andviewresolvers,torunourapplication.Thesemanagedbeansare
instantiatedduringthestartupofanapplicationbytheSpringframework.While
performingintegrationtesting,ourtestenvironmentmustalsohavethosebeanstotestour
applicationsuccessfully.TheSpringTestContextframeworkgivesustheabilitytodefine
atestcontext,whichissimilartothewebapplicationcontext(DispatcherServlet-
context.xml).Let’sseehowtoincorporateSpringTestContexttotestour
ProductValidatorclass.
Timeforaction–testingtheproduct
validator
Let’sseehowwecanbootupourtestcontextusingtheSpringTestContextframeworkto
testourProductValidatorclass:
1. Openpom.xmlandyouwillfindpom.xmlundertherootdirectoryoftheprojectitself.
2. Youwillbeabletoseesometabsatthebottomofthepom.xmlfile;selectthe
DependenciestabandclickontheAddbuttonoftheDependenciessection.
3. ASelectDependencywindowwillappear;enterGroupIdas
org.springframework,ArtifactIdasspring-test,andVersionas4.0.3.RELEASE;
thenselectScopeastest,clickontheOKbutton,andsavepom.xml.
4. NowcreateanXMLfilecalledtest-DispatcherServlet-context.xmlunderthe
com.packt.webstore.validatorpackageinthesourcefolder,src/test/resources.
Addthefollowingcodeintoitandsaveit:
<?xmlversion="1.0"encoding="UTF-8"?>
<beansxmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:webflow-config="http://www.springframework.org/schema/webflow-
config"

xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd
http://www.springframework.org/schema/webflow-config
http://www.springframework.org/schema/webflow-config/spring-webflow-
config-2.3.xsd">
<mvc:annotation-drivenvalidator="validator"/>

<context:component-scanbase-package="com.packt.webstore"/>

<beanid="messageSource"
class="org.springframework.context.support.ResourceBundleMessageSource"
>
<propertyname="basename"value="messages"/>
</bean>

<beanid="validator"
class="org.springframework.validation.beanvalidation.LocalValidatorFact
oryBean">
<propertyname="validationMessageSource"ref="messageSource"/>
</bean>

<beanid="productValidator"
class="com.packt.webstore.validator.ProductValidator">
<propertyname="springValidators">
<set>
<refbean="unitsInStockValidator"/>
</set>
</property>
</bean>

<beanid="unitsInStockValidator"
class="com.packt.webstore.validator.UnitsInStockValidator"/>

</beans>
5. Next,createaclasscalledProductValidatorTestunderthe
com.packt.webstore.validatorpackageinthesourcefolder,src/test/java.Add
thefollowingcodetoit:
packagecom.packt.webstore.domain;
packagecom.packt.webstore.validator;
importjava.math.BigDecimal;
importorg.junit.Assert;
importorg.junit.Test;
importorg.junit.runner.RunWith;
importorg.springframework.beans.factory.annotation.Autowired;
importorg.springframework.test.context.ContextConfiguration;
importorg.springframework.test.context.junit4.SpringJUnit4ClassRunner;
importorg.springframework.test.context.web.WebAppConfiguration;
importorg.springframework.validation.BindException;
importorg.springframework.validation.ValidationUtils;
importcom.packt.webstore.domain.Product;
importcom.packt.webstore.validator.ProductValidator;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("test-DispatcherServlet-context.xml")
@WebAppConfiguration
publicclassProductValidatorTest{

@Autowired
privateProductValidatorproductValidator;

@Test
publicvoidproduct_without_UnitPrice_should_be_invalid(){
//Arrange
Productproduct=newProduct();
BindExceptionbindException=newBindException(product,
"product");
//Act
ValidationUtils.invokeValidator(productValidator,product,
bindException);

//Assert
Assert.assertEquals(1,bindException.getErrorCount());

Assert.assertTrue(bindException.getLocalizedMessage().contains("Unit
priceisInvalid.Itcannotbeempty."));
}

@Test
publicvoidproduct_with_existing_productId_invalid(){
//Arrange
Productproduct=newProduct("P1234","iPhone5s",new
BigDecimal(500));
product.setCategory("Tablet");

BindExceptionbindException=newBindException(product,
"product");
//Act
ValidationUtils.invokeValidator(productValidator,product,
bindException);

//Assert
Assert.assertEquals(1,bindException.getErrorCount());
Assert.assertTrue(bindException.getLocalizedMessage().contains("A
productalreadyexistswiththisproductid."));
}

@Test
publicvoid
a_valid_product_should_not_get_any_error_during_validation(){
//Arrange
Productproduct=newProduct("P9876","iPhone5s",new
BigDecimal(500));
product.setCategory("Tablet");

BindExceptionbindException=newBindException(product,
"product");
//Act
ValidationUtils.invokeValidator(productValidator,product,
bindException);

//Assert
Assert.assertEquals(0,bindException.getErrorCount());
}
}
6. Nowright-clickonProductValidatorTestandgotoRunAs|JUnitTest.Youwill
beabletoseethetestcasesthatpass,asshowninthefollowingscreenshot:
Customerdetailscollectionform
Whatjusthappened?
AsIhavealreadymentioned,Springprovidesextensivesupportforintegrationtesting.In
ordertodevelopatestcaseusingtheSpringTestContextframework,weneedthe
spring-testjar.Instep3,wejustaddeddependencytothespring-testjar.TheSpring
TestContextframeworkcannotrunwithoutthesupportoftheJUnitjar.Instep4,wejust
createdatestwebapplicationcontextconfigurationfilecalledtest-DispatcherServlet-
context.xmlthatonlydefinesthebeansthatarerequiredforourtesttoexecute.Later,in
step5,whenwecreatedouractualtestcase,theSpringTestContextframeworkusedthis
fileasbasetocreatethetestcontext.
Step5isveryimportantbecauseitrepresentstheactualtestclass
(ProductValidatorTest)totestthevalidityofourProductdomainobject.Thegoalof
thetestclassistocheckwhetherallthevalidations(includingbeanvalidationandSpring
validation)thatarespecifiedintheProductdomainclassareworking.Ihopeyou
rememberthatwespecifiedsomeofthebeanvalidationannotation,suchas@NotNulland
@Pattern,ontheProductdomainclassinChapter7,ValidateYourProductswitha
Validator.
Onewaytotestwhetherthosevalidationsaretakingplaceisbymanuallyrunningour
applicationandtryingtoenterinvalidvalues.Thisapproachiscalledmanualtesting.This
isaverydifficultjob,whereasinautomatedtesting,wecanwritesometestclassestorun
testcasesinarepeatedfashiontotestthefunctionality.UsingJUnit,wecanwritesuch
kindsoftestclasses.
TheProductValidatorTestclasscontainsthreetestmethodsintotal;wecanidentifya
testmethodbythe@Testannotation(org.junit.Test)ofJUnit.Everytestmethodcanbe
logicallyseparatedintothreeparts,thatis,Arrange,Act,andAssert.IntheArrangepart,
weinstantiateandinstrumenttherequiredobjectsfortesting;intheActpart,weinvoke
theactualfunctionalitythatneedstobetested;andfinallyintheAssertpart,wecompare
theexpectedresultandtheactualresultthatistheoutputoftheinvokedfunctionality.
Havealookatthefollowingcode:
@Test
publicvoidproduct_without_UnitPrice_should_be_invalid(){
//Arrange
Productproduct=newProduct();
BindExceptionbindException=newBindException(product,"product");
//Act
ValidationUtils.invokeValidator(productValidator,product,
bindException);

//Assert
Assert.assertEquals(1,bindException.getErrorCount());
Assert.assertTrue(bindException.getLocalizedMessage().contains("Unit
priceisInvalid.Itcannotbeempty."));
}
IntheArrangepartofthistestmethod,wejustinstantiatedabareminimumProduct
domainobject.WehavenotsetanyvaluesfortheproductId,unitPrice,andcategory
fields.WepurposelysetupsuchabareminimumdomainobjectintheArrangepartto
checkwhetherourProductValidatorclassworksproperlyintheActpart.Accordingto
theProductValidatorclasslogic,thepresentstateoftheproductdomainobjectis
invalid.IntheActpart,weinvoketheproductValidatorobjectusingthe
ValidationUtilsclasstocheckwhetherthevalidationworksornot.Duringvalidation,
productValidatorwillstoretheerrorsinaBindExceptionobject.IntheAssertpart,we
simplycheckedwhetherthebindExceptionobjectcontainedoneerror,usingtheJUnit
AssertAPIs,andcheckedwhethertheerrormessagewasasexpected.
AnotherimportantthingweneedtounderstandinourProductValidatorTestclassisthat
weusedSpring’sstandard@Autowiredannotationtogettheinstanceof
ProductValidator;thequestionhereiswhoinstantiatedtheproductValidatorobject?
Theanswerisinthe@ContextConfigurationannotation.Notethelocationsattribute
specifiedinthe@ContextConfigurationannotation–ithasthesamenameasourtest
contextfile(test-DispatcherServlet-context.xml).
Asyoumightremember,wehavelearnedthatduringthebootingupofourapplication,
SpringMVCwillcreateawebapplicationcontext(Springcontainer)withthenecessary
beans,asdefinedinthewebapplicationcontextconfigurationfile.Weneedasimilarkind
ofcontextevenbeforerunningourtestclassessothatwecanusethosedefinedbeans
(objects)inourtestclasstotestitproperly.TheSpringTestframeworkmakesitpossible
viathe@ContextConfigurationannotation.
Nowweneedasimilarkindofrunningapplicationenvironmentwithalltheresourcefiles.
Toachievethis,weusedthe@WebAppConfigurationannotationfromtheSpringTest
framework.The@WebAppConfigurationannotationinstructstheSpringTestframeworkto
loadtheapplicationcontextasWebApplicationContext.
NowwehaveseenalmostalltheimportantthingsrelatedtoexecutingaSpringintegration
test,butonefinalconfigurationweneedtounderstandishowtointegrateJUnitandthe
SpringTestContextframeworkinourtestclass.The
@RunWith(SpringJUnit4ClassRunner.class)annotationdoesthatjob.
So,finally,whenwerunourtestcases,wewillseeagreenbarintheJUnitwindow,
indicatingthatthetestsweresuccessful.
Timeforaction–testingtheproduct
controller
Let’sseenowhowtotestourcontrollers:
1. CreateanXMLfilecalledtest-DispatcherServlet-context.xmlunderthe
com.packt.webstore.controllerpackageinthesourcefolder,
src/test/resources.Addthefollowingcodeintoitandsaveit:
<?xmlversion="1.0"encoding="UTF-8"?>
<beansxmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:webflow-config="http://www.springframework.org/schema/webflow-
config"

xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd
http://www.springframework.org/schema/webflow-config
http://www.springframework.org/schema/webflow-config/spring-webflow-
config-2.3.xsd">
<mvc:annotation-drivenvalidator="validator"/>

<context:component-scanbase-package="com.packt.webstore"/>

<bean
class="org.springframework.web.servlet.view.InternalResourceViewResolve
r">
<propertyname="prefix"value="/WEB-INF/views/"/>
<propertyname="suffix"value=".jsp"/>
</bean>


<beanid="messageSource"
class="org.springframework.context.support.ResourceBundleMessageSource"
>
<propertyname="basename"value="messages"/>
</bean>

<beanid="validator"
class="org.springframework.validation.beanvalidation.LocalValidatorFact
oryBean">
<propertyname="validationMessageSource"ref="messageSource"/>
</bean>

<beanid="productValidator"
class="com.packt.webstore.validator.ProductValidator">
<propertyname="springValidators">
<set>
<refbean="unitsInStockValidator"/>
</set>
</property>
</bean>

<beanid="unitsInStockValidator"
class="com.packt.webstore.validator.UnitsInStockValidator"/>

</beans>
2. CreateaclasscalledProductControllerTestunderthe
com.packt.webstore.controllerpackageinthesourcefolder,src/test/java,and
addthefollowingcodeintoit:
packagecom.packt.webstore.controller;
importstatic
org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get
;
importstatic
org.springframework.test.web.servlet.result.MockMvcResultMatchers.model
;
importjava.math.BigDecimal;
importorg.junit.Before;
importorg.junit.Test;
importorg.junit.runner.RunWith;
importorg.springframework.beans.factory.annotation.Autowired;
importorg.springframework.test.context.ContextConfiguration;
importorg.springframework.test.context.junit4.SpringJUnit4ClassRunner;
importorg.springframework.test.context.web.WebAppConfiguration;
importorg.springframework.test.web.servlet.MockMvc;
importorg.springframework.test.web.servlet.setup.MockMvcBuilders;
importorg.springframework.web.context.WebApplicationContext;
importcom.packt.webstore.domain.Product;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("test-DispatcherServlet-context.xml")
@WebAppConfiguration
publicclassProductControllerTest{
@Autowired
privateWebApplicationContextwac;
privateMockMvcmockMvc;
@Before
publicvoidsetup(){
this.mockMvc=
MockMvcBuilders.webAppContextSetup(this.wac).build();
}
@Test
publicvoidtestGetProducts()throwsException{
this.mockMvc.perform(get("/products"))
.andExpect(model().attributeExists("products"));
}

@Test
publicvoidtestGetProductById()throwsException{
//Arrange
Productproduct=newProduct("P1234","iPhone5s",new
BigDecimal(500));

//Act&Assert
this.mockMvc.perform(get("/products/product")
.param("id","P1234"))
.andExpect(model().attributeExists("product"))
.andExpect(model().attribute("product",product));
}
}
3. Nowright-clickontheProductControllerTestclassandgotoRunAs|JUnitTest.
Youwillbeabletoseethatthetestcasesarebeingexecuted.Youwillbeabletosee
thetestresultsintheJUnitwindow.
Whatjusthappened?
JustlikewiththeProductValidatorTestclass,weneedtobootupthetestcontextand
runourProductControllerTestclassastheSpringintegrationtest.Soweusedsimilar
annotationsontopofProductControllerTest,asfollows:
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("test-DispatcherServlet-context.xml")
@WebAppConfiguration
publicclassProductControllerTest{
ApartfromthetwotestmethodsthatareavailableunderProductControllerTest,a
singlesetupmethodisavailableasfollows:
@Before
publicvoidsetup(){
this.mockMvc=MockMvcBuilders.webAppContextSetup(this.wac).build();
}
The@Beforeannotationthatispresentontopoftheprecedingmethodindicatesthatthis
methodshouldbeexecutedbeforeeverytestmethod.Andwithinthatmethod,wesimply
buildourMockMvcobjectinordertouseitinthefollowingtestmethods.TheMockMvc
classisaspecialclassprovidedbytheSpringTestContextframeworktosimulatebrowser
actionswithinatestcase,suchasfiringHTTPrequests.Havealookatthefollowing
code:
@Test
publicvoidtestGetProducts()throwsException{
this.mockMvc.perform(get("/products"))
.andExpect(model().attributeExists("products"));
}
TheprecedingtestmethodsimplyfiresaGETHTTPrequesttoourapplicationusingthe
mockMvcobject,andasaresult,weensurethatthereturnedmodelcontainsanattribute
namedproducts.RememberthatthelistmethodintheProductControllerclassisthe
onethathandlestheprecedingwebrequest,soitwillfillthemodelwiththeavailable
productsundertheattributenamedproducts.
Afterrunningyourtestcase,youwillbeabletoseethegreenbarintheJUnitwindowthat
indicatesthetestshavepassed.
Timeforaction–testingRESTcontrollers
Similarly,wecantesttheREST-basedcontrollersaswell.Justperformthefollowing
steps:
1. Openpom.xmlandyouwillfindpom.xmlundertherootdirectoryoftheprojectitself.
2. Youwillbeabletoseesometabsatthebottomofthepom.xmlfile;selectthe
DependenciestabandclickontheAddbuttonoftheDependenciessection.
3. ASelectDependencywindowwillappear;enterGroupIdas
com.jayway.jsonpath,ArtifactIdasjson-path-assert,andVersionas0.8.1.
SelectScopeastest,clickontheOKbutton,andsavepom.xml.
4. NowcreateaclasscalledCartRestControllerTestunderthe
com.packt.webstore.controllerpackageinthesourcefolder,src/test/java.
Nowaddthefollowingcodetoit:
packagecom.packt.webstore.controller;
importstatic
org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get
;
importstatic
org.springframework.test.web.servlet.request.MockMvcRequestBuilders.put
;
importstatic
org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonP
ath;
importstatic
org.springframework.test.web.servlet.result.MockMvcResultMatchers.statu
s;
importorg.junit.Before;
importorg.junit.Test;
importorg.junit.runner.RunWith;
importorg.springframework.beans.factory.annotation.Autowired;
importorg.springframework.mock.web.MockHttpSession;
importorg.springframework.test.context.ContextConfiguration;
importorg.springframework.test.context.junit4.SpringJUnit4ClassRunner;
importorg.springframework.test.context.web.WebAppConfiguration;
importorg.springframework.test.web.servlet.MockMvc;
importorg.springframework.test.web.servlet.setup.MockMvcBuilders;
importorg.springframework.web.context.WebApplicationContext;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("test-DispatcherServlet-context.xml")
@WebAppConfiguration
publicclassCartRestControllerTest{

@Autowired
privateWebApplicationContextwac;
@Autowired
MockHttpSessionsession;

privateMockMvcmockMvc;
@Before
publicvoidsetup(){
this.mockMvc=
MockMvcBuilders.webAppContextSetup(this.wac).build();
}

@Test
publicvoidread_method_should_return_correct_cart_Json_object()
throwsException{
//Arrange
this.mockMvc.perform(put("/rest/cart/add/P1234").session(session))
.andExpect(status().is(204));

//Act
this.mockMvc.perform(get("/rest/cart/"+
session.getId()).session(session))
.andExpect(status().isOk())

.andExpect(jsonPath("$.cartItems.P1234.product.productId").value("P1234
"));
}
}
5. Nowright-clickonCartRestControllerTestandgotoRunAs|JUnitTest.You
willbeabletoseethattestcasesarebeingexecuted,andthetestresultswillbeseen
intheJUnitwindow.
Whatjusthappened?
WhiletestingRESTcontrollers,weneedtoensurethatthewebresponseforthegiven
webrequestcontainstheexpectedJSONobject.Toverifythat,weneedsomespecialized
APIstochecktheformatoftheJSONobject.Thejson-path-assertjarprovidesthese
APIs.WeaddedtheMavendependencytothejson-path-assertjarfromstep1through
3.
Instep4,wecreatedCartRestControllerTesttoverifywhetherour
CartRestControllerclassworksproperly.TheCartRestControllerTestclassisvery
similartoProductControllerTest;theonlydifferenceisthewayweasserttheresultofa
webrequest.InCartRestControllerTest,wehaveonetestmethodtotesttheread
methodoftheCartRestControllerclass.
ThereadmethodofCartRestControllerisdesignedtoreturnacartobjectasaJSON
objectforthegivencartID.InCartRestControllerTest,wehavetestedthisbehavior
throughtheread_method_should_return_correct_cart_Json_objecttestmethod.Have
alookatthefollowingcode:
@Test
publicvoidread_method_should_return_correct_cart_Json_object()throws
Exception{
//Arrange
this.mockMvc.perform(put("/rest/cart/add/P1234").session(session))
.andExpect(status().is(204));

//Act
this.mockMvc.perform(get("/rest/cart/"+
session.getId()).session(session))
.andExpect(status().isOk())

.andExpect(jsonPath("$.cartItems.P1234.product.productId").value("P1234"));
}
InordertogetacartobjectforthegivencartID,wefirstneedtostorethecartobjectin
ourcartrepositorythroughawebrequest.ThatiswhatwedidintheArrangepartofthe
precedingtestmethod.Thefirstwebrequestwefiredinthearrangepartwilladda
productdomainobjectinthecartwhoseIDisthesameasthesessionID.
IntheActpartofthetestcase,wesimplyfiredanotherREST-basedwebrequesttogetthe
cartobjectasaJSONobject.RememberthatweusedthesessionIDasourcartIDto
storeourcartobject,sowhileretrieving,weneedtogivethesamesessionIDinthe
requestURL.Forthis,wecanusethemocksessionobjectgivenbytheSpringTest
framework.Youcanseeinthefollowingcodethatwehaveautowiredthesessionobjectin
ourCartRestControllerTestclass:
this.mockMvc.perform(get("/rest/cart/"+session.getId()).session(session))
.andExpect(status().isOk())
.andExpect(
jsonPath("$.cartItems.P1234.product.productId").value("P1234"));
OncewegetthecartdomainobjectasaJSONobject,wehavetoverifythatitcontains
thecorrectproduct.WewillbeabletodothatwiththehelpofthejsonPathmethodof
MockMvcResultMatchers,asspecifiedintheprecedingcodesnippets.Aftersendingthe
RESTwebrequestgogetthecartobject,weverifiedthattheresponsestatusisas
expectedandalsocheckedwhethertheJSONobjectcontainsaproductwiththeIDP1234.
Finally,whenwerunthistestcase,youwillbeabletoseethatthetestcasesarebeing
executedandyouwillseethetestresultsintheJUnitwindow.
Haveagohero–addingtestsfortheremaining
RESTmethods
ItisgoodthatwehavetestedandverifiedthereadmethodofCartRestController,but
wehavenottestedtheothermethodsofCartRestController.Youcanaddtestsforother
methodsofCartRestControllerintheCartRestControllerTestclasstogetfamiliar
withtheSpringTestframework.
Summary
Inthisfinalchapter,youlearnedtheimportanceoftestingawebapplicationandsawhow
tounittestthedomainobject.Nextwelearnedhowtoperformintegrationteston
validatorusingtheSpringTestframework.Youalsosawhowtotestanormalcontroller
usingtheSpringTestContextframework.Asthelastexercise,yousawhowtotestREST-
basedcontrollersandhowtousethemocksessionobjectfromtheSpringTestframework.
Inthatexercise,youalsolearnedhowtoverifytheJSONpath.
AppendixA.UsingtheGradleBuildTool
Throughoutthisbook,wehaveusedApacheMavenasourbuildtool,butthereareother
popularbuildtoolsalsousedwidelyintheJavacommunity.OnesuchbuildtoolisGradle.
InsteadofXML,GradleusesaGroovy-basedDomainSpecificLanguage(DSL)asthe
baseforthebuildscript,whichprovidesmoreflexibilitywhendefiningcomplexbuild
scripts.ComparedtoMaven,Gradletakeslesstimeforincrementalbuilds.So,Gradle
buildsareveryfastandeffectiveforlargeprojects.
Inthisappendix,wewillseehowtoinstallanduseGradleasthebuildtoolinourproject.
InstallingGradle
PerformthefollowingstepstoinstallGradle:
1. GototheGradledownloadpagebyenteringtheURL
http://www.gradle.org/downloadsinyourbrowser.
2. ClickonthelatestGradlestablereleasedownloadlink;atthetimeofwritingthis,the
stablereleaseisgradle-1.11-all.zip.
3. Oncethedownloadisfinished,gotothedownloadeddirectoryandextracttheZIP
fileintoaconvenientdirectoryofyourchoice.
4. CreateanenvironmentvariablecalledGRADLE_HOME.EntertheextractedGradleZIP
directorypathasthevaluefortheGRADLE_HOMEenvironmentvariable.
5. Finally,appendtheGRADLE_HOMEvariabletoPATHbysimplyappendingthetext
;%GRADLE_HOME%\bintothePATHvariable.
NowthatyouhaveinstalledGradleonyourWindows-basedcomputer,toverifywhether
theinstallationwascompletedcorrectly,gotothecommandprompt,typegradle-v,and
pressEnter.TheoutputshowstheGradleversionandalsothelocalenvironment
configuration.
TheGradlebuildscriptforyourproject
ToconfiguretheGradlebuildscriptforyourproject,performthefollowingsteps:
1. Gototherootdirectoryofyourprojectfromthefilesystem,createafilecalled
build.gradle,andaddthefollowingcontentintothefileandsaveit:
applyplugin:'war'
applyplugin:'eclipse-wtp'
repositories{
mavenCentral()//addcentralmavenrepotoyourbuildfile
}

dependencies{
compile'org.springframework:spring-webmvc:4.0.3.RELEASE',
'javax.servlet:jstl:1.2',
'org.springframework.security:spring-security-web:3.1.4.RELEASE',
'commons-fileupload:commons-fileupload:1.2.2',
'org.apache.commons:commons-io:1.3.2',
'org.springframework:spring-oxm:4.0.3.RELEASE',
'org.codehaus.jackson:jackson-mapper-asl:1.9.10',
'log4j:log4j:1.2.12',
'org.hibernate:hibernate-validator:4.3.1.Final',
'org.springframework.webflow:spring-webflow:2.3.3.RELEASE',
'org.apache.tiles:tiles-extras:3.0.3',
'org.slf4j:slf4j-api:1.7.5'

compile('org.springframework.security:spring-security-
config:3.1.4.RELEASE'){
//excludingaparticulartransitivedependency:
excludegroup:'org.springframework',module:'spring-asm'
}

providedCompile'javax.servlet:javax.servlet-api:3.1.0'

testCompile'junit:junit:4.11',
'org.springframework:spring-test:4.0.3.RELEASE',
'com.jayway.jsonpath:json-path-assert:0.8.1'
}
2. Nowgototherootdirectoryofyourprojectfromthecommandpromptandissuethe
followingcommand:
>gradleeclipse
3. Next,openanewworkspaceinyourSTS,gotoFile|Import,selecttheExisting
ProjectsintoWorkspaceoptionfromthetreelist(youcanfindthisoptionunderthe
Generalnode),andthenclickontheNextbutton.
4. ClickontheBrowsebuttontoselecttherootdirectoryandlocateyourproject
directory.ClickonOKandthenonFinish.
Now,youwillbeabletoseeyourprojectconfiguredwiththerightdependenciesinyour
STS.
UnderstandingtheGradlescript
AtaskinGradleissimilartoagoalinMaven.TheGradlescriptsupportsmanyin-built
pluginstoexecutebuild-relatedtasks.Onesuchpluginisthewarplugin,whichprovides
manyconvenienttaskstohelpyoubuildawebproject.Wecanincorporatethesetasksin
ourbuildscripteasilybyapplyingaplugininourGradlescriptasfollows:
applyplugin:'war'
Similartothewarplugin,thereisanotherplugincalledeclipse-wtptoincorporatetasks
relatedtoconvertingaprojectintoaneclipseproject.Theeclipsecommandweusedin
step2isactuallyprovidedbytheeclipse-wtpplugin.
Insidetherepositoriessection,wecandefineourremotebinaryrepositorylocation.
WhenwebuildourGradleproject,weusethisremotebinaryrepositorytodownloadthe
requiredJARs.Inourcase,wedefinedourremoterepositoryastheMavencentral
repository,asfollows:
repositories{
mavenCentral()
}
Alloftheprojectdependenciesneedtobedefinedinsideofthedependenciessection
groupedunderthescopedeclaration,suchascompile,providedCompile,and
testCompile.Considerthefollowingcodesnippet:
dependencies{
compile
'org.springframework:spring-webmvc:4.0.3.RELEASE',
'javax.servlet:jstl:1.2'.
}
Ifyoulookcloselyatthefollowingdependencydeclarationline,thecompilescope
declaration,youseethateachdependencydeclarationlineisdelimitedwitha:(colon)
symbol,asfollows:
'org.springframework:spring-webmvc:4.0.3.RELEASE'
ThefirstpartofthepreviouslineisthegroupID,thesecondpartistheartifactID,andthe
finalpartistheversioninformationasprovidedinMaven.
So,itismorelikeaMavenbuildscriptbutdefinedusingaGradlescript,whichisbased
ontheGroovylanguage.
AppendixB.PopQuizAnswers
Chapter2,SpringMVCArchitecture–
ArchitectingYourWebStore
Popquiz–requestmapping
Q1 2
Popquiz–thewebapplicationcontext
Q1 1
Q2 3
Popquiz–webapplicationcontextconfiguration
Q1 4
Chapter3,ControlYourStorewith
Controllers
Popquiz–class-levelrequestmapping
Q1 1
Q2 2
Popquiz–requestpathvariable
Q1 4
Q2 1and4
Popquiz–therequestparameter
Q1 2
Chapter5,WorkingwithViewResolver
Popquiz–redirectview
Q1 3
Popquiz–staticview
Q1 2
Chapter6,InterceptYourStorewith
Interceptor
Popquiz–interceptor
Q1 2
Q2 2
Chapter9,ApacheTilesandSpringWeb
FlowinAction
Popquiz–webflow
Q1 3
Q2 1
Popquiz–ApacheTiles
Q1 Allthree(1,2,and3)
Index
A
actionstate,flowdefinition/Understandingtheflowdefinition
addToCartmethod,controllers.js/Whatjusthappened?
afterCompletionmethod
about/Workingwithinterceptors
Ajax
about/HandlingawebserviceinAjax
webservice,handling/HandlingawebserviceinAjax
AngularJs
using/Timeforaction–consumingRESTwebservicesviaAjax,Whatjust
happened?
URL/Whatjusthappened?
ng-repeatdirective/Whatjusthappened?
ng-clickdirective/Whatjusthappened?
ApacheTiles
reusability,enhancingthrough/EnhancingreusabilitythroughApacheTiles
views,creatingforviewstate/Timeforaction–creatingviewsforeveryview
state
templateattribute/Whatjusthappened?
<tiles*insertAttribute>tag/Whatjusthappened?
ApacheTomcat
about/Timeforaction–installingtheTomcatwebserver
URL/Timeforaction–installingtheTomcatwebserver
auditlogging
about/Auditlogging
performing,interceptorused/Auditlogging
B
@Beforeannotation/Whatjusthappened?
beanvalidationannotation
URL/Beanvalidation
buildtool
configuring/Configuringabuildtool
C
<C*forEach>tag/Whatjusthappened?
<c*if>tag/Whatjusthappened?
@Categoryannotation/Haveagohero–addingcustomvalidationtoacategory
@Componentannotation/Whatjusthappened?
@ContextConfigurationannotation/Whatjusthappened?
@Controllerannotation/Definingacontroller
about/Whatjusthappened?
cart.jspfile/Whatjusthappened?
Cartclass
creating/Timeforaction–implementingRESTfulwebservices
about/Whatjusthappened?
CartControllerclass
creating/Timeforaction–consumingRESTwebservicesviaAjax
about/Whatjusthappened?
getmethod/Whatjusthappened?
getCartmethod/Whatjusthappened?
CartItemclass
creating/Timeforaction–implementingRESTfulwebservices
about/Whatjusthappened?,Timeforaction–unit-testingdomainobjects
CartRepositoryinterface
creating/Timeforaction–implementingRESTfulwebservices
about/Whatjusthappened?
CartRestControllerclass
creating/Timeforaction–implementingRESTfulwebservices
about/Whatjusthappened?
addItemmethod/Whatjusthappened?
removeItemmethod/Whatjusthappened?
CartRestControllerTestclass/Whatjusthappened?
CartServiceImplclass
creating/Timeforaction–implementingRESTfulwebservices
CartServiceinterface
creating/Timeforaction–implementingRESTfulwebservices
about/Whatjusthappened?
categoryview
adding,toproductspage/Timeforaction–showingproductsbasedon
category,Whatjusthappened?
checkoutflowdefinition
about/Understandingthecheckoutflow
diagrammaticrepresentation/Understandingthecheckoutflow
<flow>tag/Understandingthecheckoutflow
<var>tag/Understandingthecheckoutflow
Orderclass/Understandingthecheckoutflow
ordervariable/Understandingthecheckoutflow
<action-state>definition/Understandingthecheckoutflow
validatemethod,invoking/Understandingthecheckoutflow
<evaluate>tag/Understandingthecheckoutflow
InvalidCartWarningstate/Understandingthecheckoutflow
addCartToOrderstate/Understandingthecheckoutflow
collectCustomerInfostate/Understandingthecheckoutflow
collectShippingDetailstate/Understandingthecheckoutflow
orderConfirmationstate/Understandingthecheckoutflow
processOrderstate/Understandingthecheckoutflow
thankCustomerstate/Understandingthecheckoutflow
cancelCheckoutendstate/Understandingthecheckoutflow
views,creatingforviewstates/Timeforaction–creatingviewsforeveryview
state
collectCustomerInfo.jsp,creating/Timeforaction–creatingviewsforevery
viewstate
collectShippingDetail.jsp,creating/Timeforaction–creatingviewsforevery
viewstate
orderConfirmation.jsp,creating/Timeforaction–creatingviewsforevery
viewstate
InvalidCartWarning.jsp,creating/Timeforaction–creatingviewsforevery
viewstate
thankCustomer.jsp,creating/Timeforaction–creatingviewsforeveryview
state
checkOutCancelled.jsp,creating/Timeforaction–creatingviewsforevery
viewstate
decisionstate,adding/Haveagohero–addingadecisionstate
class-levelrequestmapping
adding/Timeforaction–addingclass-levelrequestmapping,Whatjust
happened?
classesToBeBoundproperty,xmlViewbean/Whatjusthappened?
conditionalredirecting
about/Conditionalredirecting
performing,interceptorused/Conditionalredirecting
offerpagerequests,intercepting/Timeforaction–interceptingofferpage
requests
ContentNegotiatingViewResolver
about/UsingContentNegotiatingViewResolver
configuring/Timeforaction–configuringContentNegotiatingViewResolver,
Whatjusthappened?
contentnegotiation
about/UsingContentNegotiatingViewResolver
controller
defining/Definingacontroller
class-levelrequestmapping,adding/Timeforaction–addingclass-level
requestmapping,Whatjusthappened?
controllers.js
creating/Whatjusthappened?
refreshCartmethod/Whatjusthappened?
initCartIdmethod/Whatjusthappened?
clearCartmethod/Whatjusthappened?
addToCartmethod/Whatjusthappened?
removeFromCartmethod/Whatjusthappened?
CRUDoperations
about/Whatjusthappened?
customvalidationannotation
creating/Haveagohero–addingcustomvalidationtoacategory
considerations/Haveagohero–addingcustomvalidationtoacategory
customvalidationsupport
adding/Timeforaction–addingcustomvalidationsupport
D
dataauditinterceptor
adding/Timeforaction–addingthedataauditinterceptor,Whatjust
happened?
databinding,Springtaglibraries
customizing/Customizingdatabinding
formbindingwhitelisting,adding/Timeforaction–whitelistingformfields,
Whatjusthappened?
DataTransferObjects(DTOs)/Servingandprocessingforms
decisionstate,flowdefinition/Understandingtheflowdefinition
dependencyinjection(DI)
about/Thewebapplicationcontext
developmentenvironment
configuring/Configuringadevelopmentenvironment
dispatcherservlet
about/Thedispatcherservlet
Dispatcherservlet
about/Thedispatcherservlet
configuring/Timeforaction–configuringthedispatcherservlet,Whatjust
happened?
domainlayer,webapplicationarchitecture
about/Thedomainlayer
domainobject,creating/Timeforaction–creatingadomainobject,Whatjust
happened?
domainobjects
unittesting/Timeforaction–unit-testingdomainobjects,Whatjusthappened?
E
eclipse-wtpplugin/UnderstandingtheGradlescript
eclipsecommand/UnderstandingtheGradlescript
endstate,flowdefinition/Understandingtheflowdefinition
environmentvariables,JDK
settingup/Timeforaction–settingupenvironmentvariables
errorRedirectproperty,PromoCodeInterceptorclass
about/Whatjusthappened?
exceptionhandler
adding/Timeforaction–addinganexceptionhandler
F
<form*form>tag/Whatjusthappened?
<form*input>tag/Whatjusthappened?
about/Whatjusthappened?
typeattribute/Whatjusthappened?
flow-executorconfiguration/Understandingthecheckoutflow
flow-registryconfigurationtag/Understandingthecheckoutflow
flowdefinition
about/Understandingtheflowdefinition
startstate/Understandingtheflowdefinition
actionstate/Understandingtheflowdefinition
viewstate/Understandingtheflowdefinition
decisionstate/Understandingtheflowdefinition
subflowstate/Understandingtheflowdefinition
endstate/Understandingtheflowdefinition
flowHandlerAdapter/Understandingthecheckoutflow
flowHandlerMappingparameter/Understandingthecheckoutflow
foreachloop/Whatjusthappened?
forloop
about/Whatjusthappened?
form-backingbean/Whatjusthappened?
forms,Springtaglibraries
serving/Servingandprocessingforms,Timeforaction–servingand
processingforms,Whatjusthappened?
processing/Servingandprocessingforms,Timeforaction–servingand
processingforms,Whatjusthappened?
G
getCartmethod,CartControllerclass/Whatjusthappened?
getProductByIdmethod/Whatjusthappened?
getProductsByFiltermethod/Whatjusthappened?
getTotalPricemethod
about/Timeforaction–unit-testingdomainobjects
Gradle
installing/InstallingGradle
buildscript,configuring/TheGradlebuildscriptforyourproject
Gradlescript
about/UnderstandingtheGradlescript
GRADLE_HOMEvariable/InstallingGradle
H
handlerexceptionresolver
implementing/Workingwiththehandlerexceptionresolver
responsestatusexception,adding/Timeforaction–addingtheresponsestatus
exception,Whatjusthappened?
exceptionhandler,adding/Timeforaction–addinganexceptionhandler,What
justhappened?
HandlerExceptionResolverimplementations
ResponseStatusExceptionResolver/Workingwiththehandlerexception
resolver
ExceptionHandlerExceptionResolver/Workingwiththehandlerexception
resolver
HandlerInterceptorinterface
preHandlemethod/Workingwithinterceptors
postHandlemethod/Workingwithinterceptors
afterCompletionmethod/Workingwithinterceptors
HandlerMappingimplementations
about/Handlermapping
HandlerMappinginterface
about/Handlermapping
HTTPrequests
GET/Timeforaction–consumingRESTwebservices
POST/Timeforaction–consumingRESTwebservices
PUT/Timeforaction–consumingRESTwebservices
DELETE/Timeforaction–consumingRESTwebservices
I
IDE
about/Configuringadevelopmentenvironment
InitBinderannotation/Whatjusthappened?
InMemoryCartRepositoryclass
creating/Timeforaction–implementingRESTfulwebservices
about/Whatjusthappened?
InternalResourceView
about/Resolvingviews
InternalResourceViewResolver
about/Resolvingviews
internationalization
about/Internationalization(i18n)
adding/Timeforaction–addinginternationalization,Whatjusthappened?
J
Javabeanvalidation
about/Beanvalidation
adding,toproductspage/Timeforaction–addingbeanvalidationsupport,
Whatjusthappened?,Haveagohero–addingmorevalidationintheadd
productspage
customvalidationsupport,adding/CustomvalidationwithJSR-303/bean
validation,Timeforaction–addingcustomvalidationsupport,Whatjust
happened?
customvalidation,addingtocategory/Haveagohero–addingcustom
validationtoacategory
JavaRuntimeEnvironment(JRE)/Timeforaction–installingJDK
JavaServerPagesStandardTagLibrary(JSTL)/Timeforaction–addingSpringjars
totheproject,Servingandprocessingforms
JDK
about/SettingupJava
settingup/SettingupJava
installing/Timeforaction–installingJDK
environmentvariables,settingup/Timeforaction–settingupenvironment
variables
JUnit
about/Timeforaction–unit-testingdomainobjects
L
LocalValidatorFactoryBean/Whatjusthappened?
validationMessageSourceproperty/Whatjusthappened?
M
@MatrixVariableannotation/Usingmatrixvariables
@ModelAttributeannotation/Whatjusthappened?
masterdetailview
implementing/Timeforaction–implementingamasterdetailview
matrixvariables
using/Usingmatrixvariables
productlist,filtering/Timeforaction–showingtheproductsbasedonfilter,
Whatjusthappened?
enabling/Whatjusthappened?
Mavenbuildtool
installing/Timeforaction–installingtheMavenbuildtool
configuring,onSTS/Timeforaction–configuringMavenonSTS
messageattribute/Whatjusthappened?
messages_nl.propertiesfile/Whatjusthappened?
multipartrequest
about/Themultipartrequestinaction
imageuploadfacility,addingtoproductpage/Timeforaction–addingimages
totheproductpage
productusermanuals,uploadingtoserver/Haveagohero–uploadingproduct
usermanualstotheserver
multiplefilters
adding,tolistproducts/Haveagohero–addingmultiplefilterstolistproducts
N
ng-clickAngularJsdirective/Whatjusthappened?
ng-repeatAngularJsdirective/Whatjusthappened?
O
offerpagerequests,conditionalredirecting
intercepting/Timeforaction–interceptingofferpagerequests
offerRedirectproperty,PromoCodeInterceptorclass
about/Whatjusthappened?
P
@PathVariableannotation/Whatjusthappened?
pathattribute/Whatjusthappened?
persistencelayer,webapplicationarchitecture
about/Thepersistencelayer
repositoryobject,creating/Timeforaction–creatingarepositoryobject,What
justhappened?
pom.xmlfile
configuring/Timeforaction–addingJavaversionpropertiesinpom.xml
postHandlemethod
about/Workingwithinterceptors
Postman
about/Timeforaction–consumingRESTwebservices
downloadpage/Timeforaction–consumingRESTwebservices
installing/Timeforaction–consumingRESTwebservices
preHandlemethod
about/Workingwithinterceptors
processAddNewProductFormmethod/Whatjusthappened?
productcontroller
testing/Timeforaction–testingtheproductcontroller
ProductControllerTestclass
creating/Timeforaction–testingtheproductcontroller
/Whatjusthappened?
productdetailspage
creating/Timeforaction–addingtheproductdetailspage
ProductImageValidatorclass
about/Haveagohero–addingSpringvalidationtotheproductimage
productToBeAddedobject/Whatjusthappened?
productvalidator
testing/Timeforaction–testingtheproductvalidator
ProductValidatorclass/Timeforaction–testingtheproductvalidator
ProductValidatorTestclass/Whatjusthappened?
PromoCodeInterceptorclass
promoCodeproperty/Whatjusthappened?
errorRedirectproperty/Whatjusthappened?
offerRedirectproperty/Whatjusthappened?
promoCodeproperty,PromoCodeInterceptorclass
about/Whatjusthappened?
R
@Repositoryannotation/Whatjusthappened?
@RequestMappingannotation/Timeforaction–examiningrequestmapping,What
justhappened?,Definingacontroller,Whatjusthappened?
about/Whatjusthappened?
RedirectAfterPost/Whatjusthappened?
redirectview
about/Theredirectview
RedirectView
examining/Timeforaction–examiningRedirectView,Whatjusthappened?
refreshCartmethod,controllers.js/Whatjusthappened?
removeFromCartmethod,controllers.js/Whatjusthappened?
requestmapping
examining/Timeforaction–examiningrequestmapping,Whatjusthappened?
requestparameters
about/Understandingrequestparameters
productdetailspage,adding/Timeforaction–addingtheproductdetailspage
masterdetailview,implementing/Timeforaction–implementingamaster
detailview,Whatjusthappened?
multiplefilters,addingtolistproducts/Haveagohero–addingmultiplefilters
tolistproducts
responsestatusexception
adding/Timeforaction–addingtheresponsestatusexception
REST
about/IntroducingREST
RESTcontrollers
testing/Timeforaction–testingRESTcontrollers,Whatjusthappened?
RESTfulwebservices
implementing/Timeforaction–implementingRESTfulwebservices
RESTwebservices
consuming/Timeforaction–consumingRESTwebservices
consuming,viaAjax/Timeforaction–consumingRESTwebservicesvia
Ajax
S
<security*authentication-manager>tag/Whatjusthappened?
<security*http>tag/Whatjusthappened?
<spring*message>tag/Whatjusthappened?,Whatjusthappened?
servicelayer,webapplicationarchitecture
about/Theservicelayer
serviceobject,creating/Timeforaction–creatingaserviceobject,Whatjust
happened?
productdomainobject,accessing/Haveagohero–accessingtheproduct
domainobjectviaaservice
servlet-api/Timeforaction–addingSpringjarstotheproject
SessionLocaleResolverbean/Whatjusthappened?
spring-oxmnotation/Whatjusthappened?
SpringExpressionLanguage/Understandingtheflowdefinition
SpringMVC
controller,defining/Definingacontroller
controller/TheroleofacontrollerinSpringMVC
URItemplatepatterns,using/UsingURItemplatepatterns
SpringMVCarchitecture
dispatcherservlet/Thedispatcherservlet
requestmapping/Timeforaction–examiningrequestmapping
webapplicationcontext/Thewebapplicationcontext
webapplicationcontextconfigurationfile/Thewebapplicationcontext
configuration
viewresolver/Viewresolvers
webapplicationarchitecture/Anoverviewofthewebapplicationarchitecture
SpringMVCinterceptor
about/Workingwithinterceptors
HandlerInterceptorinterface/Workingwithinterceptors
configuring/Timeforaction–configuringaninterceptor,Whatjusthappened?
internationalization/Internationalization(i18n)
SpringMVCproject
creating/CreatingourfirstSpringMVCproject,Timeforaction–creatinga
SpringMVCprojectinSTS,Whatjusthappened?
dependencies,managing/SpringMVCdependencies
Springjars,adding/Timeforaction–addingSpringjarstotheproject,What
justhappened?
Javaversionproperties,addinginpom.xmlfile/Timeforaction–addingJava
versionpropertiesinpom.xml
welcomepage,creating/Ajump-starttoMVC,Timeforaction–addinga
welcomepage
welcomepage,adding/Timeforaction–addingawelcomepage,Whatjust
happened?
deploying/Deployingourproject
running/Timeforaction–runningtheproject
SpringSecurity
using/UsingSpringSecuritytags
SpringSecuritytags
using/UsingSpringSecuritytags
loginpage,adding/Timeforaction–addingaloginpage,Whatjusthappened?
Springtaglibraries
forms,serving/Servingandprocessingforms,Timeforaction–servingand
processingforms,Whatjusthappened?
forms,processing/Servingandprocessingforms,Timeforaction–servingand
processingforms,Whatjusthappened?
databinding,customizing/Customizingdatabinding
textmessages,externalizing/Externalizingtextmessages
SpringSecuritytags/UsingSpringSecuritytags
SpringTestContext
incorporating,totest/IntegrationtestingwiththeSpringTestContext
framework
SpringToolSuite(STS)/Configuringadevelopmentenvironment
installing/Timeforaction–installingSpringToolSuite
URL/Timeforaction–installingSpringToolSuite
Tomcat,configuring/Timeforaction–configuringTomcatonSTS,Whatjust
happened?
Maven,configuring/Timeforaction–configuringMavenonSTS
SpringMVCproject,creating/CreatingourfirstSpringMVCproject,What
justhappened?
Springvalidation
about/Springvalidation
using/Springvalidation
adding/Timeforaction–addingSpringvalidation,Whatjusthappened?
combining,withbeanvalidation/Timeforaction–combiningSpringandbean
validations,Whatjusthappened?
adding,toproductimage/Haveagohero–addingSpringvalidationtothe
productimage
SpringValidatorinterface/Whatjusthappened?
SpringWebFlow
about/WorkingwithSpringWebFlow
orderprocessingservice,implementing/Timeforaction–implementingthe
order-processingservice
checkoutflow,implementing/Timeforaction–implementingthecheckout
flow
flowdefinition/Understandingtheflowdefinition
checkoutflowdefinition/Understandingthecheckoutflow
application,running/Timeforaction–creatingviewsforeveryviewstate,
Whatjusthappened?
startstate,flowdefinition/Understandingtheflowdefinition
staticresources
serving/Servingstaticresources,Timeforaction–servingstaticresources,
Whatjusthappened?
images,addingtoproductdetailpage/Timeforaction–addingimagestothe
productdetailpage
subflowstate,flowdefinition/Understandingtheflowdefinition
T
testing
integrating,withSpringTestContext/IntegrationtestingwiththeSpringTest
Contextframework
tests
adding,forcart/Haveagohero–addingtestsforcart
adding,forremainingRESTmethods/Haveagohero–addingtestsforthe
remainingRESTmethods
textmessages,Springtaglibraries
externalizing/Externalizingtextmessages,Timeforaction–externalizing
messages,Whatjusthappened?
Tomcatwebserver
installing/Timeforaction–installingtheTomcatwebserver
configuring,onSTS/Timeforaction–configuringTomcatonSTS,Whatjust
happened?
transitivedependencies/Whatjusthappened?
U
UnitsInStockValidatorclass/Whatjusthappened?
unittesting
about/Unittesting
domainobjects/Timeforaction–unit-testingdomainobjects,Whatjust
happened?
URItemplatepatterns
using/UsingURItemplatepatterns
categoryview,addingtoproductspage/Timeforaction–showingproducts
basedoncategory,Whatjusthappened?
userinterface(UI)/WorkingwithSpringWebFlow
V
validationMessageSourceproperty,LocalValidatorFactoryBean/Whatjust
happened?
viewresolver
about/Viewresolvers
viewresolvers
about/Resolvingviews
views
resolving/Resolvingviews
InternalResourceView/Resolvingviews
VelocityView/Resolvingviews
FreeMarkerView/Resolvingviews
TilesView/Resolvingviews
RedirectView/Resolvingviews
redirectview/Theredirectview
viewstate,flowdefinition/Understandingtheflowdefinition
W
<web-app>tag/Timeforaction–addingaloginpage
@WebAppConfigurationannotation/Whatjusthappened?
warplugin/UnderstandingtheGradlescript
webapplicationarchitecture
domainlayer/Thedomainlayer
persistencelayer/Thepersistencelayer
servicelayer/Theservicelayer
overview/Anoverviewofthewebapplicationarchitecture
customers,listing/Haveagohero–listingallourcustomers
webapplicationcontext
about/Thewebapplicationcontext
nameandlocation,tweaking/Timeforaction–understandingtheweb
applicationcontext,Whatjusthappened?
configurationfile/Thewebapplicationcontextconfiguration
webserver
installing/Installingawebserver
webservice
handling,inAjax/HandlingawebserviceinAjax

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