SJB INSTITUTE OF TECHNOLOGY
VII Semester
LAB MANUAL
[As per Choice Based Credit System (CBCS) scheme]
(Effective from the academic year 2016 -2017)
“WEB TECHNOLOGY LABORATORY
WITH MINI PROJECT”
Subject Code: 15CSL77
BY
Assistant Professor
CHAITRA H K
MANJULA H S
SRINIDHI K S
Supporting Staff
YASHWANTH KUMAR
LOKESH K
Speakers
SANTHOSH K
Software Developer
Gowtham B C
Software Developer
DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING
SJB INSTITUTE OF TECHNOLOGY
BGS HEALTH AND EDUCATION CITY
KENGERI, BANGALORE-5600 60
2018-19
Web Technology and its Applications
WEB TECHNOLOGY LABORATORY WITH MINI PROJECT
[As per Choice Based Credit System (CBCS) scheme] (Effective
from the academic year 2016 -2017)
SEMESTER – VII
Subject Code
15CSL77
IA Marks
Number of Lecture Hours/Week
01I + 02P
Exam Marks
Total Number of Lecture Hours
40
Exam Hours
PART A
15CSL77
20
80
03
1. Write a JavaScript to design a simple calculator to perform the following operations:
sum, product, difference and quotient.
2. Write a JavaScript that calculates the squares and cubes of the numbers from 0 to 10 and outputs
HTML text that displays the resulting values in an HTML table format.
3. Write a JavaScript code that displays text “TEXT-GROWING” with increasing font
size in the interval of 100ms in RED COLOR, when the font size reaches 50pt it displays
“TEXT-SHRINKING” in BLUE color. Then the font size decreases to 5pt.
4. Develop and demonstrate a HTML5 file that includes JavaScript script that uses functions for the
following problems:
a. Parameter: A string
b. Output: The position in the string of the left-most vowel c.
Parameter: A number
d. Output: The number with its digits in the reverse order
5. Design an XML document to store information about a student in an engineering college affiliated
to VTU. The information must include USN, Name, and Name of the College, Branch, Year of
Joining, and email id. Make up sample data for 3 students. Create a CSS style sheet and use it to
display the document.
6. Write a PHP program to keep track of the number of visitors visiting the web page and to display
this count of visitors, with proper headings.
7. Write a PHP program to display a digital clock which displays the current time of the server.
8. Write the PHP programs to do the following:
a. Implement simple calculator operations.
b. Find the transpose of a matrix.
c. Multiplication of two matrices.
d. Addition of two matrices.
9. Write a PHP program named states.py that declares a variable states with value
"Mississippi Alabama Texas Massachusetts Kansas". write a PHP program that does the
following:
a. Search for a word in variable states that ends in xas. Store this word in element
0 of a list named states List.
b. Search for a word in states that begins with k and ends in s. Perform a case- insensitive
comparison. [Note: Passing re.Ias a second parameter to method compile performs a
case-insensitive comparison.] Store this word in element1 of statesList.
c. Search for a word in states that begins with M and ends in s. Store this word in
element 2 of the list.
d. Search for a word in states that ends in a. Store this word in element 3 of the list.
10. Write a PHP program to sort the student records which are stored in the database using
selection sort.
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Study Experiment / Project:
Develop a web application project using the languages and concepts learnt in the theory and
exercises listed in part A with a good look and feel effects. You can use any web technologies and
frameworks and databases.
Note:
1. In the examination each student picks one question from part A.
2. A team of two or three students must develop the mini project. However during the
examination, each student must demonstrate the project individually.
3. The team must submit a brief project report (15-20 pages) that must include the following
a. Introduction
b. Requirement Analysis
c. Software Requirement Specification d.
Analysis and Design
e. Implementation
f. Testing
Course outcomes: The students should be able to:
Design and develop dynamic web pages with good aesthetic sense of designing and latest
technical know-how's.
Have a good understanding of Web Application Terminologies, Internet Tools other web
services.
Learn how to link and publish web sites
Conduction of Practical Examination:
1. All laboratory experiments from part A are to be included for practical
examination.
2. Mini project has to be evaluated for 30 Marks.
3. Report should be prepared in a standard format prescribed for project work.
4. Students are allowed to pick one experiment from the lot.
5. Strictly follow the instructions as printed on the cover page of answer script.
6. Marks distribution:
a) Part A: Procedure + Conduction + Viva:10 + 35 +5 =50 Marks
b) Part B: Demonstration + Report + Viva voce = 15+10+05 = 30 Marks Change of experiment is
allowed only once and marks allotted to the procedure part to be made zero.
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1.Write a JavaScript to design a simple calculator to perform the following operations:
sum, product, difference and quotient.
Calculator - JavaScript and HTML
SJB Instititue of Technology
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CSS File:
#calc-contain{
position: relative;
width: 400px;
border: 2px solid black;
border-radius: 12px;
margin: 0px auto;
padding: 20px 20px 100px 20px;
}
#agh{
position: relative;
float: right;
margin-top: 15px;
}
#agh p{
font-size: 20px;
font-weight: 900;
}
input[type=button] {
background: lightGray;
width: 20%;
font-size: 20px;
font-weight: 900;
border-radius: 7px;
margin-left: 13px;
margin-top: 10px;
}
input[type=button]:active {
background-color: #3e8e41;
box-shadow: 0 5px #666;
transform: translateY(4px);
}
input[type=button]:hover {
background-color: #003300;
color: white;
}
input[type = text] {
position: relative;
display: block;
width: 90%;
margin: 5px auto;
font-size: 20px;
padding: 10px;
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box-shadow: 4px 0px 12px black inset;
}
Steps to Run:
1.
2.
3.
4.
5.
open blank page in Notepad or Notepad++
Save the XHTML file with file extension as .html and select file type as all types or all files.
Save the CSS file with file extension as .css and select file type as all types or all files.
Open the file in the browser using the URL http://localhost/filename.html
If you are using Notepad++
o Click on Run
o Select launch in any browser.( Chrome, Internet Explorer, Safari, Firefox)
Output:
2. Write a JavaScript that calculates the squares and cubes of the numbers from 0 to 10
and outputs HTML text that displays the resulting values in an HTML table format.
Steps to Run:
1. Open blank page in Notepad or Notepad++
2. Save the XHTML file with file extension as .html and select file type as all types or all
files.
3. Open the file in the browser using the URL http://localhost/filename.html
4. If you are using Notepad++
o Click on Run
o Select launch in any browser.( Chrome, Internet Explorer, Safari, Firefox)
Output:
3. Write a JavaScript code that displays text “TEXT-GROWING” with increasing font
size in the interval of 100ms in RED COLOR, when the font size reaches 50pt it
displays “TEXT-SHRINKING” in BLUE color. Then the font size decreases to 5pt.
Explanation:
The window object allows execution of code at specified time intervals.
These time intervals are called timing events.
The two key methods to use with JavaScript are:
setInterval(function, milliseconds)
Executes a function, after waiting a specified number of milliseconds, but repeats the execution of
the function continuously.This function can be used as for loop.
clearInterval(timerVariable)The clearInterval() method stops the executions of the function
specified in the setInterval() method.
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TEXT-GROWING.
TEXT-SHRININKING
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Steps to Run:
1.
2.
3.
4.
Open blank page in Notepad or Notepad++
Save the XHTML file with file extension as .html and select file type as all types or all files.
Open the file in the browser using the URL http://localhost/filename.html
If you are using Notepad++
a. Click on Run
b. Select launch in any browser.( Chrome, Internet Explorer, Safari, Firefox)
Output:
4. Develop and demonstrate a HTML5 file that includes JavaScript script that uses
functions for the following problems:
a. Parameter: A string
b. Output: The position in the string of the left-most vowel
c. Parameter: A number
d. Output: The number with its digits in the reverse order.
4a)
3A PROGRAM
Steps to Run:
1.
2.
3.
4.
Open blank page in Notepad or Notepad++
Save the XHTML file with file extension as .html and select file type as all types or all files.
Open the file in the browser using the URL http://localhost/filename.html
If you are using Notepad++
a. Click on Run
b. Select launch in any browser.( Chrome, Internet Explorer, Safari, Firefox)
Output:
4b)
Reverse Number
Steps to Run:
1.
2.
3.
4.
Open blank page in Notepad or Notepad++
Save the XHTML file with file extension as .html and select file type as all types or all files.
Open the file in the browser using the URL http://localhost/filename.html
If you are using Notepad++
a. Click on Run
b. Select launch in any browser.( Chrome, Internet Explorer, Safari, Firefox)
Output:
5. Design an XML document to store information about a student in an engineering college affiliated to
VTU. The information must include USN, Name, and Name of the College, Branch, Year of Joining, and
email id. Make up sample data for 3 students. Create a CSS style sheet and use it to display the document.
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]>
First Student Information
1JB11CS001ABCSJBITCSE2001abc@gmail.com
Second Student Information
1JB11CS002DEFSJBITCSE2001def@gmail.com
Third Student Information
1JB11CS003GHISJBITCSE2001ghi@gmail.com
CSS Document for the above XML Document
ad{display:block;}
label{font-weight:bold;color:blue;}
usn{font-size:14pt;color:red;}
name{font-size:14pt;color:red;}
college{font-size:14pt;color:red;}
branch{font-size:14pt;color:red;}
year{font-size:14pt;color:red;}
email{font-size:14pt;color:red;}
Steps to Run:
1.
2.
3.
4.
open blank page in Notepad or Notepad++
Save the XHTML file with file extension as .html and select file type as all types or all files.
Save the CSS file with file extension as .css and select file type as all types or all files.
Open the file in the browser using the URL http://localhost/filename.html
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5. If you are using Notepad++
o Click on Run
o Select launch in any browser.( Chrome, Internet Explorer, Safari, Firefox)
OUTPUT:
First Student Information
USN: 1JB11CS001
NAME:ABC
COLLEGE: SJBIT
BRANCH:CSE
YEAR:2001
EMAIL:abc@gmail.com
Second Student Information
USN: 1JB11CS002
NAME:DEF
COLLEGE: SJBIT
BRANCH:CSE
YEAR:2001
EMAIL:def@gmail.com
Third Student Information
USN: 1JB11CS003
NAME: GHI
COLLEGE: SJBIT
BRANCH:CSE
YEAR:2001
EMAIL:ghi@gmail.com
6. Write a PHP program to keep track of the number of visitors visiting the web page
and to display this count of visitors, with proper headings.
Steps to run PHP File in XAMPP:
1.
2.
3.
4.
5.
6.
Place your PHP file in the “htdocs” folder located under the XAMPP folder in your C:drive
The file path is C:\xampp\htdocs for your web server.
Make sure your PHP files are saved as such ,they should have the .php file extension .
Create file name count with the extension .txt (count.txt) and initialize to 1
Open up any web browser on your desktop and enter “localhost” into the address box
http://localhost/usrpgm/counter1.php
Output:
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7.Write a PHP program to display a digital clock which displays the current time of the
server.
In this program, we will be using the xampp browser to simulate the environment as a local server.
Navigate to: C:\xampp\php\php.ini
Line no: 1045 states the time zone of the server
Default value will be:
date.timezone=Europe/Berlin
date.timezone=Asia/Kolkata
The JavaScript function (client side) renders the time stamp of the local system.
Whereas php (server side program ) renders the time stamp from the server.
The time from the local system is:
//To display the time or server
Steps to run PHP File in XAMPP:
1.
2.
3.
4.
5.
Place your PHP file in the “htdocs” folder located under the XAMPP folder in your C:drive
The file path is C:\xampp\htdocs for your web server.
Make sure your PHP files are saved as such ,they should have the .php file extension .
Open up any web browser on your desktop and enter “localhost” into the address box
http://localhost/usrpgm/digitalclock.php
Output:
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8. Write the PHP Programs to do the following
a) Implement simple calculator operations.
POST back to the same page, hence form action=”” ( is kept empty)
Output:
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b) Transpose of a matrix & c) Addition of matrix and multiplication of two matrices.
Output:
8 Steps to run PHP File in XAMPP:
1. Place your PHP file in the “htdocs” folder located under the XAMPP folder in your
C:drive
2. The file path is C:\xampp\htdocs for your web server.
3. Make sure your PHP files are saved as such , they should have the .php file extension .
4. Open up any web browser on your desktop and enter “localhost” into the address box
5. http://localhost/usrpgm/digitalclock.php
9] Write a PHP program named states.py that declares a variable states with the value
"Mississippi Alabama Texas Massachusetts Kansas". Write a php program that does the
following:
a) Search for a word in variable states that ends in xas. Store this word in element 0 of a list
named statesList.
b) Search for a word in states that begins with k and ends in s. Perform a case insensitive
comparison. [Note: Passing re.Ias s second parameter to method compile performs a caseinsensitive comparison.]Store this word in element 1 of statesList.
c) Search for a word in states that begins with M and ends in s. Store this element in 2 of the list.
d) Search for a word in states that ends in a. Store this word in element 3 of the list.
$value ){
print( "\n" . $value." is the element ". $element);
}
?>
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Output:
The States that ends in xas:Texas
The States that ends in xas:tuxas
The states that begins with k ans ends in s:Kansas
The states that begins with M and ends in s:Massachusetts
The states that ends in a:Alabama
Texas is the element 0
tuxas is the element 1
Kansas is the element 2
Massachusetts is the element 3
Alabama is the element 4
10. Write a PHP program to sort the student records which are stored in the database
using selection sort.
Selection Sort
Add Student Record
Student ID
Name
Mobile
Email
$stu_id,
'stu_name' =>$stu_name,
'stu_mobile' =>$stu_mobile,
'stu_email' =>$stu_email
);
}
$status['studentArr'] = $studentArr;
echo json_encode($status);
mysqli_close($con);
}
/* read data from DATABASE */
if(isset($_POST['selectionSort']))
{
$sql = "select * from info";
$fetchRec = mysqli_query($con,$sql) or die(mysqli_error());
while ($row=mysqli_fetch_array($fetchRec)) {
$getStuID[]= $row['stu_id'];
}
$selectionArr = selection_sort($getStuID); // calling selection Sort function
$status['sortedArr'] = $selectionArr;
echo json_encode($status);
mysqli_close($con);
}
function selection_sort($data)
{
for($i=0; $i
Steps to run
1. Create Database in phpmyadmin. [refer student_db.sql file]
2. run file brower.
1. ajaxInfo.php - Database related file [Save, Read, SelectionSort]
2. db.php - connect to database.
3. index.php - Home file [Ajax, JSon,]
4. jquery.min.js - [it will helps to run the ajax] [given by teeachar]
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Study Experiment / Project: List of mini Project Examples
1.
2.
3.
4.
5.
6.
7.
Shopping cart
CRM(customer relationship management )
Library Management
SIMS(Student information System)
Profile Websites
Garment Root
Dashboards
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WEB TECHNOLOGY Lab VIVA Questions :css :1. What are Cascading Style Sheets?
Called (CSS) is a list of statements (or rules) that can assign various rendering properties to HTML
elements. Style rules can be specified for a single element occurrence, multiple elements, and entire
document, or even multiple documents at once.
2. What is class?
A group of instances of the same element to which a unique style can be attached.
3. What is grouping?
Gathering into a comma separated list two or more selectors that share the same style or into a
semicolon separated list two or more declarations that are attached to the same selector.
4. What is ID selector?
ID selector is an individually identified (named) selector to which a specific style is declared. Using the
ID attribute, the declared style can then be associated with one and only one HTML element per
document as to differentiate it from all the other elements. They use the # character followed by a
name.
5. What is contextual selector?
A contextual selector addresses a specific occurrence of an element. It is a string of individual selectors
separated by white space, a search pattern, where only the last element in the pattern is addressed
providing it matches the specified context. Example: “ td li {color: red} “
6. What does \ABCD (and \ABCDE) mean?
CSS allows Unicode characters to be entered by number. For example, if a class value in some Russian
document contains Cyrillic letters EL PE (Unicode numbers 041B and 041F) and you want to write a
style rule for that class, you can put that letter into the style
sheet by writing:
.\041B\041F {font-style: italic;}
This works on all keyboards, so you don’t need a Cyrillic keyboard to
write class names in Russian or another language that uses that
script.
7. What are the advantages / disadvantages of various style
methods?
External Style Sheet Advantages
– Can control styles for multiple documents at once.
– Classes can be created for use on multiple HTML element types in many documents.
– Selector and grouping methods can be used to apply styles under complex contexts.
External Style Sheet Disadvantages
– An extra download is required to import style information for each document.
– The rendering of the document may be delayed until the external style sheet is loaded.
Embedded Style Sheet Advantages
– Classes can be created for use on multiple tag types in the document.
– Selector and grouping methods can be used to apply styles under complex contexts
– No additional downloads necessary to receive style information.
Inline Style Disadvantages
– Does not distance style information from content.
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– Cannot control styles for multiple documents at once.
– Author cannot create or control classes of elements to control multiple element types within the
document.
– Selector grouping methods cannot be used to create complex element addressing scenarios.
8. What is property?
Property is a stylistic parameter (attribute) that can be influenced through CSS, e.g. font or width.
There must always be a corresponding value or values set to each property.
9. What is the CSS clear property?
The clear property specifies which sides of an element where other floating elements are not allowed.
This method cannot control styles for multiple documents at once.
Inline Style Advantages
Useful for small quantities of style definitions. Can override other style specification methods at the
local level so only exceptions need to be listed in conjunction with other style methods.
10.What are the necessities of using HTML forms?
1. Gathering user information
2. Conducting Surveys
3. Interactive services
11. What are the sequences of steps for each HTTP request
from a client to the server?
1. Making the connection
2. Making a request
3. The response
4. Closing the connection
HTML :1. What is HTML?
HTML (HyperText Markup Language) is a Universal language
whichallows an individual using special code to create web pages to be
viewed on the Internet.
2. What is a tag?
In HTML, a tag tells the browser what to do. When you write an HTML page, you enter tags for many
reasons; to change the appearance of text, to show a graphic, or to make a link to another page.
3. What is the simplest HTML page?
HTML Code:
This is my page title!
This is my message to the world!
Browser Display: This is my message to the world!
4. How do I create frames? What is a frameset?
Frames allow an author to divide a browser window into multiple (rectangular) regions. Multiple
documents can be displayed in a single window, each within its own frame. Graphical browsers allow
these frames to be scrolled independently of each other, and links can update the document displayed
in one frame without affecting the
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others. You can’t just “add frames” to an existing document. Rather, you must create a frameset
document that defines a particular combination of frames, and then display your content documents
inside those frames. The frameset document should also include alternative non-framed content in a
NOFRAMES element.
5. How can I include comments in HTML?
An HTML comment begins with “ “, and does not contain “–“ or “>” anywhere in
the comment.
6. What is a Hypertext link?
A hypertext link is a special tag that links one page to another page or resource. If you click the link,
the browser jumps to the link’s destination.
7. What is a DOCTYPE? Which one do I use?
According to HTML standards, each HTML document begins with a DOCTYPE declaration that
specifies which version of HTML the document uses. Many browsers use the document’s DOCTYPE
declaration to determine whether to use a stricter, more standardsoriented layout mode, or to use a
“quirks” layout mode that attempts to emulate older, buggy browsers.
8. Can I nest tables within tables?
Yes, a table can be embedded inside a cell in another table. The main caveat about nested tables is that
older versions of Netscape Navigator have problems with them if you don’t explicitly close you TR, TD,
and TH elements. To avoid problems, include closing tags for you TR, TD, an TH even though the
HTML specifications don’t
require them.
9. How do you align a table to the right (or left)?
You use the
property to float a table to the right. Put left in place of right to float
right.
10. How can I use tables to structure forms?
Small forms are sometimes placed within a TD element within a table. This can be useful for
positioning a form relative to other content, but it doesn’t help position the form-related elements
relative to each other. The table must be within the form and then use the table to position the form
elements.
11. How do I open a link into a new window?
Add target=”_blank” to your link syntax.
**********************************************************************************************
Java Server Pages (JSP) ::
1.What are the advantages of JSP over Servlet?
JSP is a serverside technology to make content generation a simple appear. The advantage of JSP is
that they are document-centric. Servlets, on the other hand, look and act like programs. A Java Server
Page can contain Java program fragments that instantiate and execute Java classes, but these occur
inside an HTML template file and are primarily used to generate dynamic content. Some of the JSP
functionality can be achieved on the client, using JavaScript. The power of JSP is that it is serverbased and provides a framework for Web application development.
2.What is the life-cycle of JSP?
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When a request is mapped to a JSP page for the first time, it translates the JSP page into a servlet
class and compiles the class. It is this servlet that services the client requests.
A JSP page has seven phases in its lifecycle, as listed below in the sequence of occurrence:
Translation
Compilation
Loading the class
Instantiating the class
jspInit() invocation
_jspService() invocation
jspDestroy() invocation
3.What is the jspInit() method?
The jspInit() method of the javax.servlet.jsp.JspPage interface is similar to the init() method of
servlets. This method is invoked by the container only once when a JSP page is initialized. It can be
overridden by a page author to initialize resources such as database and network connections, and to
allow a JSP page to read persistent configuration data.
4.What is the _jspService() method?
SThe _jspService() method of the javax.servlet.jsp.HttpJspPage interface is invoked every time a new
request comes to a JSP page.
This method takes the HttpServletRequest and HttpServletResponse objects as its arguments. A page
author cannot override this method, as its implementation is provided by the container.
5.What is the jspDestroy() method?
The jspDestroy() method of the javax.servlet.jsp.JspPage interface is invoked by the container when a
JSP page is about to be destroyed. This method is similar to the destroy() method of servlets. It can be
overridden by a page author to perform any cleanup operation such as closing a database connection.
6.What JSP lifecycle methods can I override?
You cannot override the _jspService() method within a JSP page. You can however, override the
jspInit() and jspDestroy() methods within a JSP page. jspInit() can be useful for allocating resources
like
database connections, network connections, and so forth for the JSP page. It is good programming
practice to free any allocated resources within jspDestroy().
7.How can I override the jspInit() and jspDestroy() methods within a JSP page?
The jspInit() and jspDestroy() methods are each executed just once during the lifecycle of a JSP page
and are typically declared as JSP
declarations:
<%!
public void jspInit() {
...
}
%>
<%!
public void jspDestroy() {
...
}
%>
8.What are implicit objects in JSP?
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Implicit objects in JSP are the Java objects that the JSP Container makes available to developers in
each page. These objects need not be declared or instantiated by the JSP author. They are
automatically
instantiated by the container and are accessed using standard variables; hence, they are called implicit
objects.The implicit objects available in JSP are as follows:
• request
• response
• pageContext
• session
• application
• out
• config
• page
• exception
The implicit objects are parsed by the container and inserted into the generated servlet code. They are
available only within the jspService method and not in any declaration.
9.What are the different types of JSP tags?
The different types of JSP tags are as follows:
10.What are JSP directives?
JSP directives are messages for the JSP engine. i.e., JSP directives serve as a message from a JSP page
to the JSP container and control the processing of the entire page They are used to set global values
such as a class declaration,
method implementation, output content type, etc.
They do not produce any output to the client.
Directives are always enclosed within <%@ ….. %> tag.
Ex: page directive, include directive, etc.
11.What is page directive?
A page directive is to inform the JSP engine about the headers or facilities that page should get from
the environment.
Typically, the page directive is found at the top of almost all of our JSP pages. There can be any
number of page directives within a JSP page (although the attribute – value pair must be unique).
The syntax of the include directive is: <%@ page
attribute=”value”>
Example:<%@ include file=”header.jsp” %>
12.What are the attributes of page directive?
There are thirteen attributes defined for a page directive of which the important attributes are as
follows:
• import: It specifies the packages that are to be imported.
• session: It specifies whether a session data is available to the JSP page.
• contentType: It allows a user to set the content-type for a page.
• isELIgnored: It specifies whether the EL expressions are ignored when a JSP is translated to a
servlet.
13. What is the include directive?
There are thirteen attributes defined for a page directive of which the important attributes are as
follows:
The include directive is used to statically insert the contents of a resource into the current JSP.
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This enables a user to reuse the code without duplicating it, and includes the contents of the specified
file at the translation time.
The syntax of the include directive is as follows:
<%@ include file = “FileName” %>
This directive has only one attribute called file that specifies the name of the file to be included.
14.What are the JSP standard actions?
The JSP standard actions affect the overall runtime behavior of a JSP page and also the response sent
back to the client.
They can be used to include a file at the request time, to find or instantiate a JavaBean, to forward a
request to a new page, to generate a browser-specific code, etc.
Ex: include, forward, useBean,etc. object
15.What are the standard actions available in JSP?
The standard actions available in JSP are as follows:
: It includes a response from a servlet or a JSP page into the current page. It differs from
an include directive in that it includes a resource at request processing time, whereas the include
directive includes a resource at translation time.
: It forwards a response from a servlet or a JSP page to another page.
: It makes a JavaBean available to a page and instantiates the bean.
: It sets the properties for a JavaBean.
: It gets the value of a property from a JavaBean component and adds it to the
response.
: It is used in conjunction with ;, ; to add a parameter to a
request. These parameters are provided using the name-value pairs.
: It is used to include a Java applet or a JavaBean in the current JSP page.
16.What is the standard action?
The standard action is used to locate an existing JavaBean or to create a JavaBean if it
does not exist. It has attributes to identify the object instance, to specify the lifetime of the bean, and
to specify the fully qualified classpath and type.
17.What are the scopes available in ?
The scopes available in are as follows:
page scope: It specifies that the object will be available for the entire JSP page but not outside the
page.
request scope: It specifies that the object will be associated with a particular request and exist as long
as the request exists.
application scope: It specifies that the object will be available throughout the entire Web application
but not outside the application.
session scope: It specifies that the object will be available throughout the session with a particular
client.
18.What is the standard action?
• The standard action forwards a response from a servlet or a JSP page to another page.
• The execution of the current page is stopped and control is transferred to the forwarded page.
• The syntax of the standard action is :
Here, targetPage can be a JSP page, an HTML page, or a servlet within the same context.
• If anything is written to the output stream that is not buffered
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before , an IllegalStateException will be thrown.
Note : Whenever we intend to use or in a page, buffering should be
enabled. By default buffer is enabled.
19.What is the standard action?
The standard action enables the current JSP page to include a static or a dynamic
resource at runtime. In contrast to the include directive, the include action is used for resources that
change
frequently. The resource to be included must be in the same context.The syntax of the
standard action is as follows:
Here, targetPage is the page to be included in the current JSP.
20.What is the difference between include directive and include action?
Include directive Include action The include directive, includes the content of the specified file during
the translation phase–when the page is converted to a servlet. The include action, includes the
response generated by executing the specified page (a JSP page or a servlet) during the request
processing phase–when the page is requested by a user. The include directive is used to statically
insert the contents of a resource into the current JSP. The include standard action enables the current
JSP page to include a static or a dynamic resource at runtime.
Use the include directive if the file changes rarely. It’s the fastest mechanism. Use the include action
only for content that changes often, and if which page to include cannot be decided until the main
page is requested.
21.Differentiate between pageContext.include and jsp:include?
The standard action and the pageContext.include() method are both used to include
resources at runtime. However, the pageContext.include() method always flushes the output of the
current page before including the other components, where as flushes the output of the
current page only if the value
of flush is explicitly set to true as follows:
22.What is the jsp:setProperty action?
You use jsp:setProperty to give values to properties of beans that have been referenced earlier. You
can do this in two contexts. First, you can use jsp:setProperty after, but outside of, a jsp:useBean
element, as below:
…
In this case, the jsp:setProperty is executed regardless of whether a new bean was instantiated or an
existing bean was found.
A second context in which jsp:setProperty can appear is inside the body of a jsp:useBean element, as
below:
…
Here, the jsp:setProperty is executed only if a new object was instantiated, not if an existing one was
found.
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23.What is the jsp:getProperty action?
The action is used to access the properties of a bean that was set using the
action. The container converts the property to a String as follows:
• If it is an object, it uses the toString() method to convert it to a String.
• If it is a primitive, it converts it directly to a String using the valueOf() method of the corresponding
Wrapper class.
• The syntax of the method is:
Here, name is the id of the bean from which the property was set. The property attribute is the
property to get. A user must create or locate a bean using the action before using the
action.
24.What is the standard action?
The standard action is used with or to pass parameter
names and values to the target resource. The syntax of the standard action is as follows:
25.What is the jsp:plugin action ?
This action lets you insert the browser-specific OBJECT or EMBED element needed to specify that the
browser run an applet using the Java plugin
26.What are scripting elements?
JSP scripting elements let you insert Java code into the servlet that will be generated from the current
JSP page. There are three forms:
1. Expressions of the form <%= expression %> that are evaluated and inserted into the output,
2. Scriptlets of the form <% code %> that are inserted into the servlet’s service method,
3. Declarations of the form <%! code %> that are inserted into the body of the servlet class, outside of
any existing methods.
27.What is a scriptlet?
A scriptlet contains Java code that is executed every time a JSP is invoked. When a JSP is translated to
a servlet, the scriptlet code goes into the service() method. Hence, methods and variables written in
scriptlets are local to the service() method. A scriptlet is written between the <% and %> tags and is
executed by the container at request processing time.
28.What are JSP declarations?
As the name implies, JSP declarations are used to declare class variables and methods in a JSP page.
They are initialized when the class is initialized. Anything defined in a declaration is available for the
whole JSP page. A declaration block is enclosed between the <%! and %> tags. A declaration is not
included in the service() method
when a JSP is translated to a servlet.
29.What is a JSP expression?
A JSP expression is used to write an output without using the out.print statement. It can be said as a
shorthand representation for scriptlets. An expression is written between the <%= and %> tags. It is
not required to end the expression with a semicolon, as it implicitly adds a semicolon to all the
expressions within the expression tags.
30.How is scripting disabled?
Scripting is disabled by setting the scripting-invalid element of the deployment descriptor to true. It is
a subelement of jsp-propertygroup. Its valid values are true and false. The syntax for disabling
scripting is as follows:
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*.jsptrue
31. What is difference between custom JSP tags and beans?
Custom JSP tag is a tag you defined. You define how a tag, its attributes and its body are interpreted,
and then group your tags into collections called tag libraries that can be used in any number of JSP
files. Custom tags and beans accomplish the same goals —encapsulating complex behavior into simple
and accessible forms.
There are several differences:
Custom tags can manipulate JSP content; beans cannot.
Complex operations can be reduced to a significantly simpler form with custom tags than with beans.
Custom tags require quite a bit more work to set up than do beans.
Custom tags usually define relatively self-contained behavior, whereas beans are often defined in one
servlet and used in a different servlet or JSP page.
Custom tags are available only in JSP 1.1 and later, but beans can be used in all JSP 1.x versions.
JAVASCRIPT ::
1.What’s relationship between JavaScript and ECMAScript?
ECMAScript is yet another name for JavaScript (other names include LiveScript). The current
JavaScript that you see supported in browsers is ECMAScript revision
2.What are JavaScript types?
Number, String, Boolean, Function, Object, Null, Undefined.
3.How do you convert numbers between different bases in
JavaScript?
– Use the parseInt() function, that takes a string as the first parameter, and the base as a second
parameter. So to convert hexadecimal 3F to decimal, use parseInt (“3F”, 16);
4.What does isNaN function do?
Return true if the argument is not a number.
5.What is negative infinity?
It’s a nuber in JavaScript, derived by dividing negative number by zero.
6.What boolean operators does JavaScript support?
– &&, || and !
7.What do “1”+2+4 evaluate to? –
Since 1 is a string, everything is a string, so the result is 124.
8.How about 2+5+”8″?
Since 2 and 5 are integers, this is number arithmetic, since 8 is a string, it’s concatenation, so 78 is the
result.
9.What looping structures are there in JavaScript? –
for, while, do-while loops, but no foreach.
10.How do you create a new object in JavaScript? –
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var obj = new Object(); or var obj = {};
11.How do you assign object properties? –
obj[“age”] = 17 or obj.age = 17.
12.What’s a way to append a value to an array? –
arr[arr.length] = value;
=>What is this keyword? –
It refers to the current object.
JavaScript gives HTML designers a programming tool – HTML authors are normally not
programmers, but JavaScript is a scripting language with a very simple syntax! Almost anyone can put
small
“snippets” of code into their HTML pages JavaScript can react to events – A JavaScript can be set to
execute
when something happens, like when a page has finished loading or when a user clicks on an HTML
element
JavaScript can read and write HTML elements – A JavaScript can read and change the content of an
HTML element
JavaScript can be used to validate data – A JavaScript can be used to validate form data before it is
submitted to a server. This saves the server from extra processing JavaScript can be used to detect the
visitor’s browser – A JavaScript
can be used to detect the visitor’s browser, and – depending on the browser – load another page
specifically designed for that browser JavaScript can be used to create cookies – A JavaScript can be
used to store and retrieve information on the visitor’s computer
13. How do I let people download a file from my page?
Once the file is uploaded to the server, you need to use an anchor reference tag to link to it.
Example: Download Foo Now!
14. What is an Empty HTML Tag?
Empty HTML tags are tags that do not need to be closed when one is creating a HTML document.
Example: br ( ,
, ) and appearance (e.g. , , ) XML
describes only content, or “meaning” HTML uses a fixed, unchangeable set of tags In XML, you make
up your own tags
3. What are the benefits of XML?
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There are many benefits of using XML on the Web :
• Simplicity- Information coded in XML is easy to read and understand, plus it can be processed easily
by computers.
• Openness- XML is a W3C standard, endorsed by software industry market leaders.
• Extensibility – There is no fixed set of tags. New tags can be created as they are needed.
• Self-description- In traditional databases, data records require schemas set up by the database
administrator. XML documents can be stored without such definitions, because they contain meta
data in the form of tags and attributes.
• Contains machine-readable context information- Tags, attributes and element structure provide
context information that can be used to interpret the meaning of content, opening up new possibilities
for highly efficient search engines, intelligent data mining, agents, etc.
• Separates content from presentation- XML tags describe meaning not presentation. The motto of
HTML is: “I know how it looks”, whereas the motto of XML is: “I know what it means, and you tell me
how it should look.” The look and feel of an XML document can be controlled by XSL style sheets,
allowing the look of a document to be
changed without touching the content of the document. Multiple views or presentations of the same
content are easily rendered.
• Supports multilingual documents and Unicode-This is important for the internationalization of
applications.
• Facilitates the comparison and aggregation of data – The tree structure of XML documents allows
documents to be compared and aggregated efficiently element by element.
• Can embed multiple data types – XML documents can contain any possible data type – from
multimedia data (image, sound, video) to active components (Java applets, ActiveX).
• Can embed existing data – Mapping existing data structures like file systems or relational databases
to XML is simple. XML supports multiple data formats and can cover all existing data structures and .
• Provides a ‘one-server view’ for distributed data – XML documents can consist of nested elements
that are distributed over multiple
remote servers. XML is currently the most sophisticated format for distributed data – the World Wide
Web can be seen as one huge XML database.
4. What is a well-formed XML document?
If a document is syntactically correct it can be called as well-formed XML documents. A well-formed
document conforms to XML’s basic rules of syntax:
• Every open tag must be closed.
• The open tag must exactly match the closing tag: XML is casesensitive.
• All elements must be embedded within a single root element.
• Child tags must be closed before parent tags.
• A well-formed document has correct XML tag syntax, but the elements might be invalid for the
specified document type.
5. What is a valid XML document
If a document is structurally correct then it can be called as valid XML documents. A valid document
conforms to the predefined rules of a specific type of document:
• These rules can be written by the author of the XML document or by someone else.
• The rules determine the type of data that each part of a document can contain.
Note:Valid XML document is implicitly well-formed, but well-formed may not be valid
7. What is a Processing Instruction in XML?
A ProcessingIntruction is the information which we would like to give to application. Through a
ProcessingInstruction an application would get idea about how to process the document.
A ProcessingInstruction can appear anywhere and any no. of times in a document.
8. How does the XML structure is defined?
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XML document will have a structure which has to be defined before we can create the documents and
work with them. The structural rules can be defined using many available technologies, but the
following are popular way of doing so
• Document Type Definition (DTD)
• Schema
9. What is DTD?
A Document Type Definition (DTD) defines the legal building blocks of an XML document. It defines
rules for a specific type of document, including:
• Names of elements, and how and where they can be used
• The order of elements
• Proper nesting and containment of elements
• Element attributes
To apply a DTD to an XML document, you can:
• Include the DTD’s element definitions within the XML document itself.
• Provide the DTD as a separate file, whose name you reference in the XML document.
10. What is XML Schema?
An XML Schema describes the structure of an XML instance document by defining what each element
must or may contain.XML Schema is expressed in the form of a separate XML file.
• XML Schema provides much more control on element and attribute datatypes.
• Some datatypes are predefined and new ones can be created.
•
11. What are differences between DTDs and Schema?
Schema DTD Schema document is an XML document i.e., the structure of an XML
document is specified by another XML document. DTDs follow
SGML syntax.
Schema supports variety of dataTypes similar to programming language. In DTD everything is treated
as text.
In Schema, It is possible to inherit and create relationship among elements. This is not possible in
DTD without invalidating existing documents.
In Schema, It is possible to group elements and attributes so that they can be treated as single logical
unit. Grouping of elements and attributes is not possible in DTD.
In Schemas, it is possible to specify an upper limit for the number of occurrences of an element It is
not possible to specify an upper limit of an element in DTDs
12. What is a Complex Element?
A complex element is an XML element that contains other elements
and/or attributes.
There are four kinds of complex elements:
• empty elements
• elements that contain only other elements
• elements that contain only text
• elements that contain both other elements and text
13. What is a Simple Element?
A simple element is an XML element that can contain only text.
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• A simple element cannot have attributes
• A simple element cannot contain other elements
• A simple element cannot be empty
• However, the text can be of many different types, and may have various restrictions applied to it
14. What are namespaces? Why are they important?
A simple element is an XML element that can contain only text.
• Namespaces are a simple and straightforward way to distinguish names used in XML documents, no
matter where they come from.
• XML namespaces are used for providing uniquely named elements and attributes in an XML
instance
• They allow developers to qualify uniquely the element names and relationships and make these
names recognizable, to avoid name collisions on elements that have the same name but are defined in
different vocabularies.
• They allow tags from multiple namespaces to be mixed, which is essential if data is coming from
multiple sources.
Example: a bookstore may define the tag to mean the title of a book, contained only within
the <BOOK> element. A directory of people, however, might define <TITLE> to indicate a person’s
position, for instance: <TITLE>President. Namespaces help define this distinction clearly.
Note: a) Every namespace has a unique name which is a string. To maintain the uniqueness among
namespaces a IRL is most preferred approach, since URLs are unique.
b) Except for no-namespace Schemas, every XML Schema uses at least two namespaces:
1.the target namespace.
2. The XMLSchema namespace (http://w3.org/2001/XMLSchema)
15. What are the ways to use namespaces?
There are two ways to use namespaces:
• Declare a default namespace
• Associate a prefix with a namespace, then use the prefix in the XML to refer to the namespace
16. What is the relevance of Element Form Default attribute in the Schema?
Element Form Default indicates whether or not locally declared elements must be qualified by the
target namespace in an instance document. Element Form Default attribute in the Schema has the
following relevance:
• Qualified: Each and every element of the Schema must be qualified with the namespace in the
instance document.
• Unqualified: means only globally declared elements must be qualified with there namespace and not
the local elements.
17.What is XML parser?
An XML parser is a piece of software which can do following:
• Check for well-formedness
• Validate the document
• Allows us to read, create or modify existing XML documents Note: Parser is piece of software
provided by vendors. An XML parser is built in Java runtime from JDK 1.4 onwards
18.What is DOM?
The Document Object Model (DOM) is a platform and language independent standard object model
for representing XML and related formats. DOM is standard API which is not specific to any
programming language. DOM represents an XML document as a tree model. The tree model makes
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the XML document hierarchal by nature. Each and every construct of the XML document is
represented as a node in the tree.
19.What is SAX?
SAX-Simple API for XML processing. SAX provides a mechanism for reading data from an XML
document. It is a popular alternative to the Document Object Model (DOM).SAX provides an event
based processing approach unlike DOM which is tree based.
20.What are the interfaces of SAX?
The interfaces of SAX are:
• Document Handler- is used for getting event notification relating to a document.
• DTDHandler- is implemented to get the notifications related to declarations in DTD like entities and
notations
• EntityResolver- is used for reading external entities.
• ErrorHandler- is used for handling error related notifications.
21.What is the difference between SAX parser and DOM parser?
SAX DOM
A SAX parser takes the occurrences of components of an input document as events (i.e., event based
processing), and tells the client what it reads as it reads through the input document. A DOM parser
creates a tree structure in memory from an input document and then waits for requests from client.
No navigation possible (top to bottom only once) Whereas, we can navigate the DOM tree in any
direction, any no. of times. We cannot modify the document content in SAX We can modify the
document content in DOM .
A SAX parser serves the client application always only with pieces of the document at any given time.
A DOM parser always serves the client application with the entire document no matter how much is
actually needed by the client.
A SAX parser, however, is much more space efficient in case of a big
input document A DOM parser is space inefficient when the document is huge.
Use SAX parser when
• Input document is too big for available memory.
• When only a part of the document is to be read and we create the data structures of our own.
• If you use SAX, you are using much less memory and performing much less dynamic memory
allocation.
Use DOM when
• Your application has to access various parts of the document and using your own structure is just as
complicated as the DOM tree.
• Your application has to change the tree very frequently and data has to be stored for a significant
amount of time.
22.What is a CDATA section in XML?
CDATA Sections are used to escape blocks of text containing characters which would otherwise be
recognized as markup. All tags and entity references are ignored by an XML processor that treats
them just like any character data. CDATA blocks have been provided as a convenience measure when
you want to include large blocks of
special characters as character data, but you do not want to have to use entity references all the time.
23.What is XSL?
eXtensible Stylesheet Language(XSL) deals with most displaying the
contents of XML documents.XSL consists of three parts:
• XSLT – a language for transforming XML documents
• XPath – a language for navigating in XML documents
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• XSL-FO – a language for formatting XML documents
24.How is XSL different from Cascading Style Sheets? Why is a new Stylesheet language needed?
XSL is compatible with CSS and is designed to handle the new capabilities of XML that CSS can’t
handle. XSL is derived from Document Style Semantics and Specification Language (DSSSL), a
complex Stylesheet language with roots in the SGML community. The syntax of XSL is quite different
from CSS, which could be used to display simple XML data but isn’t general enough to handle all the
possibilities generated by XML. XSL adds the capability to handle
these possibilities. For instance, CSS cannot add new items or generated text (for instance, to assign a
purchase order number) or add a footer (such as an order confirmation). XSL allows for these
capabilities.
25.What is XSLT?
eXtensible Stylesheet Language Transformation (XSLT) deals withtransformation of one XML
document into XHTML documents or to other XML documents. XSLT uses XPath for traversing an
XML document and arriving at a particular node.
SERVLET
1.What is the Servlet?
A servlet is a Java programming language class that is used to extend the capabilities of servers that
host applications accessed by means of a request- response programming model.
2.What are the new features added to Servlet 2.5?
Following are the changes introduced in Servlet 2.5: • A new dependency on J2SE 5.0
• Support for annotations
• Loading the class
• Several web.xml conveniences
• A handful of removed restrictions
• Some edge case clarifications
3.What are the uses of Servlet?
Typical uses for HTTP Servlets include:
• Processing and/or storing data submitted by an HTML form.
• Providing dynamic content, e.g. returning the results of a database query to the client.
• A Servlet can handle multiple request concurrently and be used to develop high performance system
• Managing state information on top of the stateless HTTP, e.g. for an online shopping cart system
which manages shopping carts for many concurrent customers and maps every request to the right
customer.
4.What are the advantages of Servlet over CGI?
Servlets have several advantages over CGI:
• A Servlet does not run in a separate process. This removes the overhead of creating a new process for
each request.
• A Servlet stays in memory between requests. A CGI program (and probably also an extensive
runtime system or interpreter) needs to be loaded and started for each CGI request.
• There is only a single instance which answers all requests concurrently. This saves memory and
allows a Servlet to easily manage persistent data.
• Several web.xml conveniences
• A handful of removed restrictions
• Some edge case clarifications
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5.What are the phases of the servlet life cycle?
The life cycle of a servlet consists of the following phases:
• Servlet class loading : For each servlet defined in the deployment descriptor of the Web application,
the servlet container locates and loads a class of the type of the servlet. This can happen when the
servlet engine itself is started, or later when a client request is actually delegated to the servlet.
• Servlet instantiation : After loading, it instantiates one or more object instances of the servlet class
to service the client requests.
• Initialization (call the init method) : After instantiation, the container initializes a servlet before it is
ready to handle client requests. The container initializes the servlet by invoking its init() method,
passing an object implementing the ServletConfig interface. In the init() method, the servlet can read
configuration parameters
from the deployment descriptor or perform any other one-time activities, so the init() method is
invoked once and only once by the servlet container.
• Request handling (call the service method) : After the servlet is initialized, the container may keep it
ready for handling client requests. When client requests arrive, they are delegated to the servlet
through the service() method, passing the request and response objects as parameters. In the case of
HTTP requests, the request and response objects are implementations of HttpServletRequest and
HttpServletResponse respectively. In the HttpServlet class, the service() method invokes a different
handler method for each type of HTTP request, doGet() method for GET
requests, doPost() method for POST requests, and so on.
• Removal from service (call the destroy method) : A servlet container may decide to remove a servlet
from service for various reasons, such as to conserve memory resources. To do this, the servlet
container calls the destroy() method on the servlet. Once the destroy() method has been called, the
servlet may not service any more client requests.
Now the servlet instance is eligible for garbage collection The life cycle of a servlet is controlled by the
container in which the servlet has been deployed.
6.Why do we need a constructor in a servlet if we use the init method?
Even though there is an init method in a servlet which gets called to initialize it, a constructor is still
required to instantiate the servlet.
Even though you as the developer would never need to explicitly call the servlet’s constructor, it is still
being used by the container (the container still uses the constructor to create an instance of the
servlet). Just like a normal POJO (plain old java object) that might have an init method, it is no use
calling the init method if you haven’t constructed an object to call it on yet.
7.How the servlet is loaded?
A servlet can be loaded when:
• First request is made.
• Server starts up (auto-load).
• There is only a single instance which answers all requests concurrently. This saves memory and
allows a Servlet to easily manage persistent data.
• Administrator manually loads.
8.How a Servlet is unloaded?
A servlet is unloaded when:
• Server shuts down.
• Administrator manually unloads.
9.What is Servlet interface?
The central abstraction in the Servlet API is the Servlet interface. All servlets implement this interface,
either directly or , more commonly by extending a class that implements it.
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Note: Most Servlets, however, extend one of the standard implementations of that interface, namely
javax.servlet.GenericServlet andjavax.servlet.http.HttpServlet.
10.What is the GenericServlet class?
GenericServlet is an abstract class that implements the Servlet interface and the ServletConfig
interface. In addition to the methods declared in these two interfaces, this class also provides simple
versions of the lifecycle methods init and destroy, and implements the log method declared in the
ServletContext interface. Note: This class is known as generic servlet, since it is not specific to any
protocol.
11.What’s the difference between GenericServlet and HttpServlet?
GenericServlet HttpServlet
The GenericServlet is an abstract class that is extended by HttpServlet to provide HTTP protocolspecific methods. An abstract class that simplifies writing HTTP servlets. It extends the GenericServlet
base class and provides an framework for handling the HTTP protocol.
The GenericServlet does not include protocol-specific methods for handling request parameters,
cookies, sessions and setting response headers. The HttpServlet subclass passes generic service
method requests to the relevant doGet() or doPost() method.
GenericServlet is not specific to any protocol. HttpServlet only supports HTTP and HTTPS protocol.
12.Why is HttpServlet declared abstract?
The HttpServlet class is declared abstract because the default implementations of the main service
methods do nothing and must be overridden. This is a convenience implementation of the Servlet
interface, which means that developers do not need to implement all service methods. If your servlet
is required to handle doGet() requests for example, there is no need to write a doPost() method
too.
13.Can servlet have a constructor ?
One can definitely have constructor in servlet.Even you can use the constrctor in servlet for
initialization purpose,but this type of approch is not so common. You can perform common
operations with the constructor as you normally do.The only thing is that you cannot call that
constructor explicitly by the new keyword as we normally do.In the case of servlet, servlet container is
responsible for instantiating the servlet, so the constructor is also called by servlet container only.
14.What are the types of protocols supported by HttpServlet ?
It extends the GenericServlet base class and provides a framework for handling the HTTP protocol.
So, HttpServlet only supports HTTP and HTTPS protocol.
15.What is the difference between doGet() and doPost()?
# doGet() doPost()
1 In doGet() the parameters are appended to the URL and sent along with header information. In
doPost(), on the other hand will (typically) send the information through a socket back to the
webserver and it won’t show up in the URL bar.
2 The amount of information you can send back using a GET is restricted as URLs can only be 1024
characters. You can send much more information to the server this way – and it’s not restricted to
textual data either. It is possible to send files and even binary data such as serialized Java objects!
3 doGet() is a request for information; it does not (or should not) change anything on the server.
(doGet() should be idempotent) doPost() provides information (such as placing an order for
merchandise) that the server is expected to remember
4 Parameters are not encrypted Parameters are encrypted
5 doGet() is faster if we set the response content length since the same connection is used. Thus
increasing the performance doPost() is generally used to update or post some information to the
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server.doPost is slower compared to doGet since doPost does not write the content length
6 doGet() should be idempotent. i.e. doget should be able to be repeated safely many times This
method does not need to be idempotent. Operations requested through POST can have side
effects for which the user can be held accountable.
7 doGet() should be safe without any side effects for which user is held responsible This method does
not need to be either safe
8 It allows bookmarks. It disallows bookmarks.
16.When to use doGet() and when doPost()?
Always prefer to use GET (As because GET is faster than POST),
except mentioned in the following reason:
• If data is sensitive
• Data is greater than 1024 characters
• If your application don’t need bookmarks.
17.How do I support both GET and POST from the same Servlet?
The easy way is, just support POST, then have your doGet method
call your doPost method:
public void doGet(HttpServletRequest request, HttpServletResponse
response)
throws ServletException, IOException
{
doPost(request, response);
}
18. Should I override the service() method?
We never override the service method, since the HTTP Servlets have already taken care of it . The
default service function invokes the doXXX() method corresponding to the method of the HTTP
request.For example, if the HTTP request method is GET, doGet() method is called by default. A
servlet should override the doXXX() method for the HTTP methods that servlet supports. Because
HTTP service method check the request method and calls the appropriate handler method, it is not
necessary to override the service method itself. Only override the appropriate doXXX() method.
19.How the typical servlet code look like ?
20.What is a servlet context object?
A servlet context object contains the information about the Web application of which the servlet is a
part. It also provides access to the resources common to all the servlets in the application. Each Web
application in a container has a single servlet context associated with it.
21.What are the differences between the ServletConfig interface and the ServletContext interface?
ServletConfig ServletContext
The ServletConfig interface is implemented by the servlet container in order to pass configuration
information to a servlet. The server passes an object that implements the ServletConfig interface to the
servlet’s init() method. A ServletContext defines a set of methods that a servlet uses to communicate
with its servlet container.
There is one ServletConfig parameter per servlet. There is one ServletContext for the entire webapp
and all the servlets in a webapp share it.
The param-value pairs for ServletConfig object are specified in the within the
tags in the web.xml file The param-value pairs for ServletContext object are specified in the
tags in the web.xml file.
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22.What’s the difference between forward() and sendRedirect()
methods?
forward() sendRedirect()
A forward is performed internally by the servlet. A redirect is a two step process, where the web
application instructs the browser to fetch a second URL, which differs from the original.
The browser is completely unaware that it has taken place, so itsoriginal URL remains intact. The
browser, in this case, is doing the work and knows that it’s making a new request.
Any browser reload of the resulting page will simple repeat the original request, with the original URL
A browser reloads of the second URL ,will not repeat the original request, but will rather fetch
the second URL.
Both resources must be part of the same context (Some containers make provisions for cross-context
communication but this tends not to be very portable) This method can be used to redirect users to
resources that are not part of the current context, or even in the same domain. Since both resources
are part of same context, the original request context is retained Because this involves a new request,
the previous request scope objects, with all of its parameters and attributes are no
longer available after a redirect. (Variables will need to be passed by via the session object).
Forward is marginally faster than redirect. redirect is marginally slower than a forward, since it
requires two browser requests, not one.
23.What is the difference between the include() and forward() methods?
include() forward()
The RequestDispatcher include() method inserts the the contents of the specified resource directly in
the flow of the servlet response, as if it were part of the calling servlet. The RequestDispatcher
forward() method is used to show a different resource in place of the servlet
that was originally called. If you include a servlet or JSP document, the included resource must
not attempt to change the response status code or HTTP headers, any such request will be ignored.
The forwarded resource may be another servlet, JSP or static HTML document, but the response is
issued under the same URL that was originally requested. In other words, it
is not the same as a redirection.
The include() method is often used to include common “boilerplate”text or template markup that may
be included by many servlets. The forward() method is often used where a servlet is taking a controller
role; processing some input and deciding the outcome by returning a particular response page.
24.What’s the use of the servlet wrapper classes??
The HttpServletRequestWrapper and HttpServletResponseWrapper classes are designed to make it
easy for developers to create custom implementations of the servlet request and response types. The
classes are constructed with the standard HttpServletRequest and HttpServletResponse instances
respectively and their default behaviour is to pass all method calls directly to the underlying
objects.
26.What is a deployment descriptor?
A deployment descriptor is an XML document with an .xml extension. It defines a component’s
deployment settings. It declares transaction attributes and security authorization for an enterprise
bean. The information provided by a deployment descriptor is declarative and therefore it can be
modified without changing the source code of a bean. The JavaEE server reads the deployment
descriptor at run time and acts upon the component accordingly.
27.What is the difference between the getRequestDispatcher(String path)
javax.servlet.ServletRequest interface and javax.servlet.ServletContext interface?
ServletRequest.getRequestDispatcher(String path)
ServletContext.getRequestDispatcher(String path)
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The getRequestDispatcher(String path) method
ofjavax.servlet.ServletRequest interface accepts parameter the path to the resource to be included or
forwarded to, which can be relative to the request of the calling servlet. If the path begins with a “/” it
is interpreted as relative to the current context root. The getRequestDispatcher(String path) method
ofjavax.servlet.ServletContext interface cannot accept relative paths. All path must start with a “/” and
are interpreted as relative to current context root.
28.What is preinitialization of a servlet?
A container does not initialize the servlets as soon as it starts up, it
initializes a servlet when it receives a request for that servlet first
time. This is called lazy loading. The servlet specification defines the
element, which can be specified in the deployment descriptor to
make the servlet container load and initialize the servlet as soon as it
starts up. The process of loading a servlet before any request comes
in is called preloading or preinitializing a servlet.
29.What is the element?
The element of a deployment descriptor is used to load a servlet file when the
server starts instead of waiting for the first request. It is also used to specify the order in which the
files are to be loaded. The element is written in the
deployment descriptor as follows:
ServletNameClassName1
Note: The container loads the servlets in the order specified in the element.
30.What is session?
A session refers to all the requests that a single client might make to a server in the course of viewing
any pages associated with a given application. Sessions are specific to both the individual user and the
application. As a result, every user of an application has a separate session and has access to a
separate set of session variables.
31.What is Session Tracking?
Session tracking is a mechanism that servlets use to maintain state about a series of requests from the
same user (that is, requests originating from the same browser) across some period of time.
32.What is the need of Session Tracking in web application?
HTTP is a stateless protocol i.e., every request is treated as new request. For web applications to be
more realistic they have to retain information across multiple requests. Such information which is
part of the application is reffered as “state”. To keep track of this state we need session tracking.
Typical example: Putting things one at a time into a shopping cart, then checking out–each page
request must somehow be associated with previous requests.
33.What are the types of Session Tracking ?
Sessions need to work with all web browsers and take into account the users security preferences.
Therefore there are a variety of ways to send and receive the identifier:
• URL rewriting : URL rewriting is a method of session tracking in which some extra data (session ID)
is appended at the end of each URL. This extra data identifies the session. The server can associate
this session identifier with the data it has stored about that session. This method is used with
browsers that do not support cookies or where the user has disabled the cookies.
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• Hidden Form Fields : Similar to URL rewriting. The server embeds new hidden fields in every
dynamically generated form page for the client. When the client submits the form to the server the
hidden fields identify the client.
• Cookies : Cookie is a small amount of information sent by a servlet to a Web browser. Saved by the
browser, and later sent back to the server in subsequent requests. A cookie has a name, a single value,
and optional attributes. A cookie’s value can uniquely identify a client.
• Secure Socket Layer (SSL) Sessions : Web browsers that support Secure Socket Layer
communication can use SSL’s support via HTTPS for generating a unique session key as part of the
encrypted conversation.
34.How do I use cookies to store session state on the client?
In a servlet, the HttpServletResponse and HttpServletRequest objects passed to method
HttpServlet.service() can be used to create cookies on the client and use cookie information
transmitted during client requests. JSPs can also use cookies, in scriptlet code or, preferably,
from within custom tag code.
• To set a cookie on the client, use the addCookie() method in class HttpServletResponse. Multiple
cookies may be set for the same request, and a single cookie name may have multiple values.
• To get all of the cookies associated with a single HTTP request, use the getCookies() method of class
HttpServletRequest
35.What are some advantages of storing session state in cookies?
• Cookies are usually persistent, so for low-security sites, user data that needs to be stored long-term
(such as a user ID, historical information, etc.) can be maintained easily with no server
interaction. • For small- and medium-sized session data, the entire session data
(instead of just the session ID) can be kept in the cookie.
36.What are some disadvantages of storing session state in cookies?
• Cookies are controlled by programming a low-level API, which is more difficult to implement than
some other approaches.
• All data for a session are kept on the client. Corruption, expiration or purging of cookie files can all
result in incomplete, inconsistent, or missing information.
• Cookies may not be available for many reasons: the user may have disabled them, the browser
version may not support them, the browser may be behind a firewall that filters cookies, and so on.
Servlets and JSP pages that rely exclusively on cookies for client-side session state will not operate
properly for all clients. Using cookies, and then switching to an alternate client-side session state
strategy in cases where cookies aren’t available, complicates development and maintenance.
• Browser instances share cookies, so users cannot have multiple simultaneous sessions.
• Cookie-based solutions work only for HTTP clients. This is because cookies are a feature of the HTTP
protocol. Notice that the while package javax.servlet.http supports session management (via class
HttpSession), packagejavax.servlet has no such support.
37.What is URL rewriting?
URL rewriting is a method of session tracking in which some extra data is appended at the end of each
URL. This extra data identifies the session. The server can associate this session identifier with the
data it has stored about that session.
Every URL on the page must be encoded using method
HttpServletResponse.encodeURL(). Each time a URL is output, the servlet passes the URL to
encodeURL(), which encodes session ID in the URL if the browser isn’t accepting cookies, or if the
session tracking is turned off.
E.g., http://abc/path/index.jsp;jsessionid=123465hfhs Advantages
• URL rewriting works just about everywhere, especially when cookies are turned off.
• Multiple simultaneous sessions are possible for a single user.
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Session information is local to each browser instance, since it’s stored in URLs in each page being
displayed. This scheme isn’t foolproof, though, since users can start a new browser instance using a
URL for an active session, and confuse the server by interacting with the same session through two
instances.
• Entirely static pages cannot be used with URL rewriting, since every link must be dynamically
written with the session state. It is possible to combine static and dynamic content, using (for
example) templating or server-side includes. This limitation is also a barrier to
integrating legacy web pages with newer, servlet-based pages.
DisAdvantages
• Every URL on a page which needs the session information must be rewritten each time a page is
served. Not only is this expensive computationally, but it can greatly increase communication
overhead.
• URL rewriting limits the client’s interaction with the server to HTTP GETs, which can result in
awkward restrictions on the page.
• URL rewriting does not work well with JSP technology.
• If a client workstation crashes, all of the URLs (and therefore all of the data for that session) are lost.
38.How can an existing session be invalidated?
An existing session can be invalidated in the following two ways:
• Setting timeout in the deployment descriptor: This can be done by specifying timeout between the
tags as follows:
10
This will set the time for session timeout to be ten minutes.
• Setting timeout programmatically: This will set the timeout for a specific session. The syntax for
setting the timeout programmatically is as follows:
public void setMaxInactiveInterval(int interval)
The setMaxInactiveInterval() method sets the maximum time in seconds before a session becomes
invalid.
Note :Setting the inactive period as negative(-1), makes the container stop tracking session, i.e, session
never expires.
39.How can the session in Servlet can be destroyed?
An existing session can be destroyed in the following two ways:
• Programatically : Using session.invalidate() method, which makes the container abonden the session
on which the method is called.
• When the server itself is shutdown.
40.A client sends requests to two different web components. Both of the components access the
session. Will they end up using the same session object or different session ?
Creates only one session i.e., they end up with using same session . Sessions is specific to the client but
not the web components. And there is a 1-1 mapping between client and a session.
41.What is servlet lazy loading?
• A container doesnot initialize the servlets ass soon as it starts up, it initializes a servlet when it
receives a request for that servlet first time. This is called lazy loading.
• The servlet specification defines the element, which can be specified in the
deployment descriptor to make the servlet container load and initialize the servlet as soon as it starts
up.
• The process of loading a servlet before any request comes in is called preloading or preinitializing a
servlet.
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42.What is Servlet Chaining?
Servlet Chaining is a method where the output of one servlet is piped into a second servlet. The output
of the second servlet could be piped into a third servlet, and so on. The last servlet in the chain returns
the output to the Web browser.
43.How are filters?
Filters are Java components that are used to intercept an incoming request to a Web resource and a
response sent back from the resource. It is used to abstract any useful information contained in
the request or response. Some of the important functions performed by filters are as follows:
• Security checks
• Modifying the request or response
• Data compression
• Logging and auditing
• Response compression
Filters are configured in the deployment descriptor of a Web application. Hence, a user is not required
to recompile anything to change the input or output of the Web application.
44.What are the functions of an intercepting filter?
The functions of an intercepting filter are as follows:
• It intercepts the request from a client before it reaches the servlet and modifies the request if
required.
• It intercepts the response from the servlet back to the client and modifies the request if required.
• There can be many filters forming a chain, in which case the output of one filter becomes an input to
the next filter. Hence, various modifications can be performed on a single request and response.
45.What are the functions of the Servlet container?
The functions of the Servlet container are as follows:
• Lifecycle management : It manages the life and death of a servlet, such as class loading,
instantiation, initialization, service, and making servlet instances eligible for garbage collection.
• Communication support : It handles the communication between the servlet and the Web server.
• Multithreading support : It automatically creates a new thread for every servlet request received.
When the Servlet service() method completes, the thread dies.
• Declarative security : It manages the security inside the XML deployment descriptor file.
• JSP support : The container is responsible for converting JSPs to servlets and for maintaining them.
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