servlet notes.doc

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Chapter Four

Servlet(Server Side programming)

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Servlets are server side components that provide a powerful mechanism for

developing server side programs.

Servlets provide component-based, platform-independent methods for

building Web-based applications.

Servlets are server as well as platform-independent. Using servlets web

developerscan create fast and efficient server side application which can run

on any servlet enabled web server.

Servlets run entirely inside the Java Virtual Machine. Since the Servlet runs at

server side so it does not checs the browser for compatibility. Servlets can

access the entire family of Java !"#s, including the J$%& !"# to access

enterprise databases. Servlets can also access a library of '(("-specific calls,

receive all the benefits of the mature )ava language including portability,

performance, reusability, and crash protection. Servlets are the popular choice

for building interactive web applications.

Servlets are not designed for a specific protocol. %ut they are most commonly

used with the '((" protocols.

Servlets uses the classes in the )ava pacages )ava*.servlet and

)ava*.servlet.http. Servlets provides a way of creating the sophisticated server
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side e*tensions in a server as they follow the standard framewor and use the

highly portable )ava language.

'((" Servlet typically used to+

"rovide dynamic content lie getting the results of a database uery and

returning to the client.

"rocess andor store the data submitted by the '(M.

Manage information about the state of a stateless '((". e.g. an online

shopping car manages reuest for multiple concurrent customers.

Life cycle of Servlet

/. oading and #nstantiation: (he servlet container loads the servlet during

startup or when the first reuest is made. (he loading of the servlet depends

on the attribute 0load-on-startup1 of web.*ml file. #f the attribute 0load-on-

startup1 has a positive value then the servlet is load with loading of the

container otherwise it load when the first reuest comes for service. !fter

loading of the servlet, the container creates the instances of the servlet.

2. #nitiali3ation: !fter creating the instances, the servlet container calls the init45

method and passes the servlet initiali3ation parameters to the init45 method.

(he init45 must be called by the servlet container before the servlet can service
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any reuest. (he initiali3ation parameters persist until the servlet is destroyed.

(he init45 method is called only once throughout the life cycle of the servlet.

(he servlet will be available for service if it is loaded successfully otherwise

the servlet container unloads the servlet.

6. Servicing the 7euest: !fter successfully completing the initiali3ation

process, the servlet will be available for service. Servlet creates separate

threads for each reuest. (he servlet container calls the service45 method for

servicing any reuest. (he service45 method determines the ind of reuestand calls the appropriate method 4do8et45 or do"ost455 for handling the

reuest and sends response to the client using the methods of the response

ob)ect.

9. $estroying the Servlet: #f the servlet is no longer needed for servicing any

reuest, the servlet container calls the destroy45 method . ie the init45

method this method is also called only once throughout the life cycle of the

servlet. &alling the destroy45 method indicates to the servlet container not to

sent any reuest for service and the servlet releases all the resources

associated with it. Java Virtual Machine claims for the memory associated

with the resources for garbage collection.


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ife &ycle of a Servlet

Advantages of Java Servlets

/. Portability

2. Powerful

6. Efficiency


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9. Safety

:. Integration

;. Extensibility

t do. Servlets can share data among each other, they even mae

the database connection pools easy to implement. (hey can maintain the session by

using the session tracing mechanism which helps them to maintain information

from reuest to the reuest. #t can do many other things which are difficult to

implement in the &8# programs.

?fficiency

!s compared to &8# the servlets invocation is highly efficient. When the servlet getloaded in the server, it remains in the server>s memory as a single ob)ect instance.

'owever with servlets there are = threads but only a single copy of the servlet class.

Multiple concurrent reuests are handled by separate threads so we can say that the

servlets are highly scalable.


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Safety

!s servlets are written in )ava, servlets inherit the strong type safety of )ava

language. Java>s automatic garbage collection and a lac of pointers means that

servlets are generally safe from memory management problems. #n servlets we can

easily handle the errors due to Java>s e*ception handling mechanism. #f any

e*ception occurs then it will throw an e*ception.

#ntegration

Servlets are tightly integrated with the server. Servlet can use the server to translate

the file paths, perform logging, chec authori3ation, and M#M? type mapping etc.

?*tensibility

(he servlet !"# is designed in such a way that it can be easily e*tensible. !s it

stands today, the servlet !"# support 'ttp Servlets, but in later date it can be

e*tended for another type of servlets.

#ne*pensive

(here are number of free web servers available for personal use or for commercial

purpose. Web servers are relatively e*pensive. So by using the free available web

servers you can add servlet support to it.

Advantages of Servlets over CGI

Servlets are server side components that provide a powerful mechanism for

developing server web applications for server side. ?arlier &8# was developed to

provide server side capabilities to the web applications. !lthough &8# played a

ma)or role in the e*plosion of the #nternet, its performance, scalability and

reusability issues mae it less than optimal solutions. Java Servlets changes all that.


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%uilt from ground up using Sun>s write once run anywhere technology )ava servlets

provide e*cellent framewor for server side processing.

Using servlets web developers can create fast and efficient server side applications

and can run it on any servlet enabled web server. Servlet runs entirely inside the Java

Virtual Machine. Since the servlet runs on server side so it does not depend on

browser compatibility.

Servlets have a number of advantages over &8# and other !"#>s. (hey are+

"latform#ndependence

Servlets are written entirely in )ava so these are platform independent. Servlets

can run on any Servlet enabled web server. @or e*ample if you develop an web

application in windows machine running Java web server, you can easily run the

same on apache web server 4if !pache Serve is installed5 without modification or

compilation of code. "latform independency of servlets provides great

advantages over alternatives of servlets.

"erformance

$ue to interpreted nature of )ava, programs written in )ava are slow. %ut the )ava

servlets runs very fast. (hese are due to the way servlets run on web server. @or

any program initiali3ation taes significant amount of time. %ut in case of

servlets initiali3ation taes place first time it receives a reuest and remains in

memory till times out or server shut downs. !fter servlet is loaded, to handle a

new reuest it simply creates a new thread and runs service method of servlet. #n

comparison to traditional &8# scripts which creates a new process to serve the

reuest.


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?*tensibility

Java Servlets are developed in )ava which is robust, well-designed and ob)ect

oriented language which can be e*tended or polymorphed into new ob)ects. So

the )ava servlets tae all these advantages and can be e*tended from e*isting

class to provide the ideal solutions.

Safety

Java provides very good safety features lie memory management, e*ception

handling etc. Servlets inherits all these features and emerged as a very powerful

web server e*tension.

Secure

Servlets are server side components, so it inherits the security provided by the

web server. Servlets are also benefited with Java Security Manager.

Introduction to Java Servlets

Java Servlets are server side Java programs that reuire either a Web Server or an

!pplication Server for e*ecution. ?*amples for Web Servers include !pacheAs

(omcat Server and MacromediaAs J7un. !pplication Servers include #%MAs

Weblogic and %?!As Websphere server. ?*amples for other Server programs

include Java Server "ages 4JS"s5 and ?nterprise Java %eans 4?J%s5.

%asic Servlet Structure


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Java servlets are server side programs or to be more specific, web applications that

run on servers that comply '((" protocol. (he )ava*.servlet and )ava*.servlet.http

pacages provide the necessary interfaces and classes to wor with servlets. Servlets

generally e*tend the 'ttpServlet class and override the do8et or the do"ost methods.

#n addition, other methods such as init45, service45 and destroy45 also called as life

cycle methods might be used. (he seleton of a servlet is given in "rogramm.


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Servlets Life Cycle

(he first time a servlet is invoed, it is the init method which is called. !nd

remember that this is called only once during the lifetime of a servlet. So,

you can put all your initiali3ation code here.

(his method ne*t calls the service method. (he service method in turn

calls the do8et or do"ost methods 4whichever the user has overridden5.

@inally, the servlet calls the destroy method. #t is in a sense euivalent to

the finally method. Bou can reset or close references connections done

earlier in the servletAs methods 4e.g. init, service or do8et do"ost5. !fter

this method is called, the servlet ceases to e*ist for all practical purposes.

'owever, please note that it is not mandatory to override all these


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methods. More often than not, it is the do8et or do"ost method used with

one or more of the other life cyclemethods.

! Servlet "rogram


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Cutput Screens

(o appreciate the e*ecution of the servlet life cycle methods, eep refreshing the

browser 4@: in Windows5. #n the bacground, what actually happens is D with


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each refresh, the do8et method is called which increments iAs value and displays

the current value.


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Installation, Configuration and running Servlets

#n this section, we will see as how to install a Web Server, configure it and finally

run servlets using this server. (hroughout this tutorial, we will be using !pacheAs
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(omcat server as the Web Server. (omcat is not only an open and free server, but

also the most preferred Web Server across the world. ! few reasons we can attribute

for its popularity is D ?asy to install and configure, very less memory footprint, fast,

powerful and portable. #t is the ideal server for learning purpose.

#nstallation of (omcat Server and J$E

!s mentioned earlier, !pacheAs (omcat Server is free softwareavailable for

download F www.apache.org. (he current version of (omcat Server is ;.G 4as of

=ovember 2GG


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successfully installed as follows+

Step /

K 8o to &+I"rogram @ilesI!pache Software @oundationI(omcat ;.GIbin and double

clic on tomcat;

C7

K 8o to Start-1"rograms-1!pache (omcat ;.G -1 Monitor (omcat. Bou will notice

an icon appear on the right side of your Status %ar. 7ight clic on this icon and

clic on Start service.

Step 2

K Cpen your %rowser 4e.g. MS #nternet ?*plorer5 and type the following U7 +

http+localhost 4#f you have changed to port L to G5

C7

K Cpen your %rowser 4e.g. MS #nternet ?*plorer5 and type the following U7 +

http+localhost+GG 4#f you have =C( changed the default port L5

#n either case, you should get a page similar to the one in @igure- which signifies

that the (omcat Server is successfully running on your machine.

&ompile and ?*ecute your Servlet

(his section through a step by step 4and illustration5 approach e*plains as how to

compile and then run a servlet using (omcat Server. (hough this e*planation is

specific to (omcat, the procedure e*plained holds true for other Web servers too.

your servlet progra" Step#$%o"pile


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(he first step is to compile your servlet program. (he procedure is no different from

that of writing and compiling a )ava program. %ut, the point to be noted is that

neither the )ava*.servlet. nor the )ava*.servlet.http. is part of the standard J$E. #t

has to be e*clusively added in the &!SS"!('. (he set of classes reuired for

writing servlets is available in a )ar file called servlet-api.)ar. (his )ar file can be

downloaded from several sources. 'owever, the easiest one is to use this )ar file

available with the (omcat server 4&+I"rogram @ilesI!pache Software

@oundationI(omcat ;.GIlibIservlet-api.)ar5. Bou need to include this path in

&!SS"!('. Cnce you have done this, you will be able to successfully compile

your servlet program. ?nsure that the class file is created successfully.

Step & $ %reate your Web application fol'er

(he ne*t step is to create your web applicationfolder. (he name of the folder can be

any valid and logical name that represents your application 4e.g. banHapps,

airlineHticetsHbooing, shoppingHcart,etc5. %ut the most important criterion is that

this folder should be created under webapps folder. (he path would be similar or

close to this - &+I"rogram @ilesI!pache Software @oundationI(omcat ;.GIwebapps.

@or demo purpose, let us create a folder called demo-e*amples under the webapps

folder.
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@igure- depicts the same.

Step $ %reate the WE)*I+ fol'er

(he third step is to create the W?%-#=@ folder. (his folder should be created under

your web application folder that you created in the previous step. @igure-/G shows

the W?%-#=@ folder being placed under the demo-e*amples folder.

@igureD W?%-#=@ folder inside web application folder

Step- $%reate the web.x"l file an' the classes fol'er

(he fourth step is to create the web.*ml file and the classes folder. ?nsure that the


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web.*ml and classes folder are created under the W?%-#=@ folder. @igure-// shows

this file and folder being placed under the W?%-#=@ folder.

@igure D web.*ml file and the classes folder

=ote D #nstead of creating the web.*ml file an easy way would be to copy an

e*isting web.*ml file 4e.g. &+I"rogram @ilesI!pache Software @oundationI(omcat

;.GIwebappsIe*amplesIW?%-#=@5 and paste it into this folder. Bou can later edit

this file and add relevant information to your web application.

Step / $ %opy the servlet class to the classes fol'er

We need to copy the servlet class file to the classes folder in order to run the servlet

that we created. !ll you need to do is copy the servlet class file 4the file we obtained

from Step /5 to this folder. @igure-/2 shows the servletHlifecycle5 class being placed

in the classes folder.


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@igure D servlet class file placed under classes folder

Step 0 $ E'it web.x"l to inclu'e servlet1s na"e an' url pattern

(his step involves two actions vi3. including the servletAs name and then mentioning

the url pattern. et us first see as how to include the servletAs name in the web.*ml

file. Cpen the web.*ml file and include the servletAs name as shown in @igure-/6.


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@igureD #nclude servletAs name using the 0servlet1 0servlet1 tag

+ote $ (he servlet-name need not be the same as that of the class name. Bou can

give a different name 4or alias5 to the actual servlet. (his is one of the main reasons

as why this tag is used for.

=e*t, include the url pattern using the 0servlet-mapping1 0servlet-mapping1 tag.

(he url pattern defines as how a user can access the servlet from the browser.

@igure-/9 shows the url pattern entry for our current servlet.


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@igure D #nclude url-pattern using the 0servlet-mapping1 0servlet-mapping1 tag

+oteD "lease remember that the path given in the url-pattern is a relative path. (his

means that this path is w.r.t. your web applications folder 4demo-e*amples in this

case5.

Step 2 $ Run 3o"cat server an' then execute your Servlet

(his step again involves two actions vi3. running the Web Server and then e*ecuting

the servlet. !fter ensuring that the web server is running successfully, you can run

your servlet. (o do this, open your web browser and enter the url as specified in the

web.*ml file. (he complete url that needs to be entered in the browser is+

http+localhostdemoe*amplesservletHlifecycle


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@igure D Cur servletAs outputN

Bou can eep refreshing the browser window and see for yourself as how i value is

incremented 4a proof that the do8et is called every time you re-invoe a servlet5.

'ow to 7un a Servlet

(o run a servlet one should follow the steps illustrated below+

4ownloa' an' Install the to"cat server: #nstall the tomcat server in a

directory in which you want to install and set the classpath.for the variable

5678O9E in the environment variable. (o get details about the

installation process and setting the classpath clic the lin (omcat installation.

Set the class for the ar file: Set the classpath of the servlet-api.)ar file in the

variable %;SSP38 inside the environment variable by using the

following steps.

@or Windows O",
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8o to Start-1&ontrol "anel-1System-1!dvanced-1?nvironment Variables-

1=ew button and Set the values as

6ariable +a"e: %;SSP38

6ariable 6alue: &+I"rogram @ilesIJavaI(omcat ;.GIlibIservlet-api.)ar

@or Windows 2GGGand =(

8o to Start-1Settings-1&ontrol "anel-1System-1?nvironment Variables-

1=ew button and Set the values as

6ariable +a"e: %;SSP38

6ariable 6alue: &+I"rogram @ilesIJavaI(omcat ;.GIlibIservlet-api.)ar

&reate a )ava source file and a web.*ml file in a 'irectory structure.

&ompile the )ava source file, put the compiled file 4.class file5 in the classes

folder of your applicationand deploy the directory of your application in the

webapps folder inside the tomcat directory.

Start the tomcat server, open a browser window and type the U7

http:


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method whenever web server receives the 8?( reuest from the servlet. (he

do8et45 method taes two arguments first is 'ttpServlet7euest ob)ect and the

second one is 'ttpServlet7esponse ob)ect and this method throws the

Servlet?*ception.

Whenever the user sends the reuest to the server then server generates two ob)ects,

first is 'ttpServlet7euest ob)ect and the second one is 'ttpServlet7esponse ob)ect.

'ttpServlet7euest ob)ect represents the client>s reuest and the

'ttpServlet7esponse represents the servlet>s response.

#nside the do8et445 method our servlet has first used the set&ontent(ype45method ofthe response ob)ect which sets the content type of the response to text/html. #t is the

standard M#M? content type for the 'tml pages. !fter that it has used the method

getWriter45 of the response ob)ect to retrieve a PrintWriter ob)ect. (o display the

output on the browser we use the println45 method of the PrintWriterclass.

3he co'e the progra" is given below:

import )ava.io.*;import javax.servlet.*;import javax.servlet.http.*;

public class HelloWorld extends HttpServlet{public void doGet(HttpServletRequest request, HttpServle throws ServletException response.set"ontent#$pe(%text&ht'l%;

)rintWriter p + response.etWriter(; p.println(%-ht'l%; p.println(%-head-titleHello World-&title-&title% p.println(%-/od$%; p.println(%-h0Hello World-&h0%; p.println(%-&/od$-&ht'l%; 1
http://roseindia.net/servlets/HelloWorld.shtmlhttp://roseindia.net/servlets/HelloWorld.shtml


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1

web.x"l file for this progra":

-2x'l version+%0.3% encodin+%S!4556740%2-844-89!"#:)E e/4app

)


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4isplaying 4ate in Servlet

#n this e*ample we are going to show how we can display a current date and time on

our browser. #t is very easy to display it on our browser by using the 4ateclass of

theava.utilpacage.

3he co'e the progra" is given below:

import )ava.io.*;

import java.util.*;

import javax.servlet.*;

import javax.servlet.http.*;

public class 9ispla$in9ate extends HttpServlet{

public void doGet(HttpServletRequest request, HttpServletResponse response

throws ServletException, !Exce

)rintWriter p + response.etWriter(;

9ate toda$ + new 9ate(;

p.println(%-ht'l%D%-/od$-h0#oda$ 9ate is-&h0%;

p.println(%-/%D toda$D%-&/-&/od$%D %-&ht'l%;

1

1
http://roseindia.net/servlets/DisplayingDate.shtmlhttp://roseindia.net/servlets/DisplayingDate.shtml


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web.x"l file for this progra"

-2x'l version+%0.3% encodin+%S!4556740%2

-844-89!"#:)E e/4app

)


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Simple Counter in Servlet

#n this e*ample we are going to now how we can mae a program on counterwhich

will eep trac how many times the servlet has been accessed.

(o mae this program firstly we have to mae one class Si"ple%ounterInServlet.

(he name of the class should follow the naming convention. 7emember to eep the

name of the class in such a way that it becomes easy to understand what the program

is going to do )ust by seeing the class name. !fter maing a class define one variable

counter which will eep record for how many times the servlet has been accessed.

=ow use method either 'o?et(! or 'oPost(! to write a logic of the program. Cur

program logic is simple. We have to )ust increment the value of the counter by /. (o

display the output use the method getWriter(!method of the response ob)ect which

will in turn return the ob)ect of the "rintWriter class. =ow display the value of the

counter.

3he co'e of the progra" is given below:
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import )ava.io.*;



public class Si'ple"ounter extends HttpServlet{

int counter + 3;

public void doGet(HttpServletRequest request, HttpServletResponse response

throws ServletException, !Exception

{

response.set"ontent#$pe(%text&ht'l%;


counterDD; p.println(%t present the value oF the counter is % D

1

1

3he output of the progra" is given below:

Holistic Counter

#n this program we are going to mae a such a servlet which will count the number it

has been accessed and the number of threads created by the server.
http://roseindia.net/servlets/SimpleCounterInServlet.shtmlhttp://roseindia.net/servlets/HolisticCounterInServlet.shtmlhttp://roseindia.net/servlets/SimpleCounterInServlet.shtmlhttp://roseindia.net/servlets/HolisticCounterInServlet.shtml


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#n this e*ample firstly we are going to create one class named as

'olistic&ounter#nServlet. =ow declare a variable counterof init with initial value G,

the value of this counter will be different for each servlet and create a 8ashtable

ob)ect. (his ob)ect will be shared by all the threads in the container. #nside the

do8et45 method use the method getWriter45 method of the response ob)ect which

will return the "rintWriter ob)ect.


import )ava.io.*;

import java.io.!Exception;import java.util.*;



public class Holistic"ounter extends HttpServlet{

int counter + 3; &&separate or Each Servlet

static Hashta/le hash#a/le + new Hashta/le(; &&Shared /$

public void doGet(HttpServletRequest request, HttpServletR

throws ServletException, !

{

response.set"ontent#$pe(%text&ht'l%;


counterDD;

p.println(%#his servlet has /een accessed% D counter D

hash#a/le.put(this,this;

p.println(%#here are currentl$% D hash#a/le.sie( D %t
http://roseindia.net/servlets/HolisticCounterInServlet.shtmlhttp://roseindia.net/servlets/HolisticCounterInServlet.shtmlhttp://roseindia.net/servlets/HolisticCounterInServlet.shtmlhttp://roseindia.net/servlets/HolisticCounterInServlet.shtml


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1

1


Counter in init( !et"od

#n this program we are going to mae such a servlet which will count and displays

the number of times it has been accessed and by reading the init parameter to now

from where the counting will begin.

#n this program we are going to mae use of the init method of the Servletinterface

which taes one argument of Servlet&onfig. @irstly declare a variable counter which

will have the initial value of the counter. (he init45 method accepts an ob)ect which

implements Servlet&onfig interface. #t uses the method get#nit"arameter45 method


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of the Servlet&onfig interface to the value of the init parameter initialwhich we

have defined in the deployment descriptor file. Bou need to parsethe String value

which you will get from the getInitPara"eter(! method to a #nteger.


import )ava.io.*;



public class "ounternnit extends HttpServlet { int counter;

public void init(Servlet"onFi conFi throws ServletExc

super.init(conFi;

Strin initIalue + conFi.etnit)ara'eter(%initial%;

try{

counter + nteer.parsent(initIalue;

1

catch(Au'/eror'atException e

{

counter + 3;

1

1

protected void doGet(HttpServletRequest request, HttpSer

throws ServletException, !Exception {response.set


counterDD;

p.println(%Since loadin this servlet has /een accessed
http://roseindia.net/servlets/CounterInInit.shtmlhttp://roseindia.net/servlets/CounterInInit.shtml


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1

1



)


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-e/4app-servlet -servlet4na'eHello-&servlet4na'e -servlet4class"ounternnit-&servlet4class-&servlet

-servlet4'appin-servlet4na'eHello-&servlet4na'e-url4pattern&"ounternnit-&url4pattern-&servlet4'appin-&e/4app


Getting Init #arameter $ames

#n this e*ample we are going to retrieve the init parameter values which we have

given in the web.x"lfile.

Whenever the container maes a servlet it always reads it deployment descriptor file

i.e. web.*ml. &ontainer creates namevalue pairs for the Servlet%onfig ob)ect. Cnce

the parameters are in Servlet%onfigthey will never be read again by the &ontainer.

(he main )ob of the Servlet%onfig ob)ect is to give the init parameters.

(o retrieve the init parameters in the program firstly we have made one class named

?ettingInitPara"eter+a"es. (he container calls the servlet>s service(! method

then depending on the type of reuest, the service method calls either the do8et45 or


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the do"ost45. %y default it will be do8et45 method. =ow inside the 'o?et(! method

use getWriter(! method of the responseob)ect which will return a ob)ect of the

"rintWriter class which helps us to print the content on the browser.

(o retrieve all the values of the init parameter use method

getInitPara"eter+a"es(!which will return the ?numeration of the init parameters.


import )ava.io.*;import javax.servlet.*;import javax.servlet.http.*;

import java.util.*;

public class nitServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response throws ServletException, !Exception { )rintWriter p + response.etWriter(; p.print(%nit )ara'eters are B %; Enu'eration enu'eration + etServlet"onFi(.etnit)ara'eterAa'es(; while(enu'eration.has>oreEle'ents({ p.print(enu'eration.nextEle'ent( D % %; 1 p.println(%Jn#he e'ail address is % D etServlet"onFi(.etnit)ara'eter(%d'inE'a p.println(%#he address is % D etServlet"onFi(.etnit)ara'eter(%ddress%;

p.println(%#he phone no is % D etServlet"onFi(.etnit)ara'eter(%)honeAo%; 11

web.x"l file of this progra":
http://roseindia.net/servlets/GettingInitParameterNames.shtmlhttp://roseindia.net/servlets/GettingInitParameterNames.shtml


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-2x'l version+%0.3% encodin+%S!4556740%2-89!"#:)E e/4app

)


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(his is a very simple e*ample in which we are going to display the name on the

browser which we have entered from the 'tml page.

(o get the desired result firstly we have to mae one html form which will have only

one field named as name in which we will enter the name. !nd we will also have

one submit button, on pressing the submit button the reuest will go to the server

and the result will be displayed to us.

#n the servlet which will wor as a controller here pics the value from the html page

by using the method getPara"eter(!. (he output will be displayed to you by the

ob)ect of the PrintWriterclass.


-ht'l-head-titleAe )ae 0-&title-&head

-/od$

-h?=oin-&h?-p)lease enter $our userna'e and passord-&p-For' 'ethod+%GE#% action+%&ht'lFor'&=oinServlet% -p serna'e -input t$pe+%text% na'e+%userna'e% sie+%?3%-&p -p )assord -input t$pe+%text% na'e+%passord% sie+%?3%-&p -p-input t$pe+%su/'it% value+%Su/'it% na'e+%


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Strin pass + request.et)ara'eter(%passord%; out.println(%-ht'l%; out.println(%-/od$%; out.println(%#hanLs >r.% D % % D na'e D % % D %For visitin roseindia-/r% out.println(%Ao $ou can see $our passord B % D % % D pass D %-/r%; out.println(%-&/od$-&ht'l%;

11


-2x'l version+%0.3% encodin+%S!4556740%2-844-89!"#:)E e/4app)


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!ultiple values for a single parameter

#n our program it may be that we may have multiples values for a single parameter

lie in checbo*es. We are going to mae one program over it.

(o mae such a servlet in which we have made one html form from where the values

will be passed to the controller. #n this program we have used the checbo* which

will have the same name but with different values. We have one more submit button,

on pressing this button the reuest will be forwarded.


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=ow in the servlet that is woring lie a controller will retrieve the values we have

entered in the html form by the method getPara"eter6alues(!which returns the

arrayof String. !t last to retrieve all the values from the array use for loop. (he

output will be displayed to you by the PrintWriterob)ect.


In'ex.ht"l

-89!"#:)E H#>= )= N.30 #ransitional&&EA%

-ht'l-head-titlensert title here-&title-&head-/od$-For' 'ethod + %post% action + %&Get)ara'eterServlet&Get)ara'eterIalues%-pWhich oF the hisL$ $ou liLe 'ost-&p

-input t$pe + %checL/ox% na'e +%hisL$% value + %Ro$al"hallene%Ro$al"hallene.--input t$pe + %checL/ox% na'e +%hisL$% value + %Ro$alSta%Ro$alSta.-/r-input t$pe + %checL/ox% na'e +%hisL$% value + %


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import java.io.*;import javax.servlet.*;import javax.servlet.http.*;

public class Get)ara'eterIalues extends HttpServlet{protected void do)ost(HttpServletRequest request, HttpServletResponse response throws ServletException, !Exception { response.set"ontent#$pe(%text&ht'l%; )rintWriter p + response.etWriter(; StrinOP hisL$ + request.et)ara'eterIalues(%hisL$%; for(int i+3; i-hisL$.lenth; iDD{ p.println(%-/rhisL$ B % D hisL$OiP; 1 11



)


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8ere is the result of the above selection:

Send 'edirect in Servlet

When we want that someone else should handle the response of our servlet, then

there we should use sen'Re'irect(!method.


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#n send 7edirect whenever the client maes any reuest it goes to the container,

there the container decides whether the concerned servlet can handle the reuest or

not. #f not then the servlet decides that the reuest can be handle by other servlet

or )sp. (hen the servlet calls the sen'Re'irect(!method of the response ob)ect and

sends bac the response to the browser along with the status code. (hen the browser

sees the status code and loo for that servlet which can now handle the reuest.

!gain the browser maes a new reuest, but with the name of that servlet which can

now handle the reuest and the result will be displayed to you by the browser. #n all

this process the client is unaware of the processing.

#n this e*ample we are going to mae one html in which we will submit the user

name and his password. (he controller will chec if the password entered by the

user is correct or not. #f the password entered by the user is correct then the servlet

will redirect the reuest to the other servlet which will handle the reuest. #f the

password entered by the user is wrong then the reuest will be forwarded to the html

form.

3he co'e of the exa"ple is given below:

ht"l file for this progra":

-ht'l

-head-titleAe )ae 0-&title-&head

-/od$

-For' 'ethod+%)!S#% action+%&SendRedirect&SendRedirectServlet% -pEnter $our na'eMn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp; -input t$pe+%text% na'e+%userna'e% sie+%?3%-&p -pEnter $our passordMn/sp; -input t$pe+%text% na'e+%passord% sie+%?3%-&p


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-pMn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp; Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp;Mn/sp; -input t$pe+%su/'it% value+%Su/'it% na'e+%


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-2x'l version+%0.3% encodin+%S!4556740%2-89!"#:)E e/4app)


48/103


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Session rac)ing

!s we now that the 'ttp is a statelessprotocol, means that it can>t persist the

information. #t always treats each reuest as a new reuest. #n 'ttp client maes aconnection to the server, sends the reuest., gets the response, and closes the

connection.

#n session management client first mae a reuest for any servlet or any page, the

container receives the reuest and generates a uniue session #$ and gives it bac to

the client along with the response. (his #$ gets stores on the client machine.

(hereafter when the client reuest again sends a reuest to the server then it also

sends the session #d with the reuest. (here the container sees the #d and sends bac

the reuest.

Session (racing can be done in three ways+

/. 8i''en or" iel's:(his is one of the ways to support the session tracing.

!s we now by the name, that in this fields are added to an '(M form

which are not displayed in the client>s reuest . (he hidden form fields are sent

bac to the server when the form is submitted. #n hidden form fields the html

entry will be lie this + 0input type QPhiddenP name Q PnameP valueQPP1. (his

means that when you submit the form, the specified name and value will be

get included in get or post method. #n this session #$ information would be

embedded within the form as a hidden field and submitted with the 'ttp

"CS( command.

2. @R; Rewriting: (his is another way to support the session tracing.

@R;Rewritingcan be used in place where we don>t want to use cooies. #t is

used to maintain the session. Whenever the browser sends a reuest then it is


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always interpreted as a new reuest because http protocol is a stateless

protocol as it is not persistent. Whenever we want that out reuest ob)ect to

stay alive till we decide to end the reuest ob)ect then, there we use the

concept of session tracing. #n session tracing firstly a session ob)ect is

created when the first reuest goes to the server. (hen server creates a toen

which will be used to maintain the session. (he toen is transmitted to the

client by the response ob)ect and gets stored on the client machine. %y default

the server creates a cooie and the cooie get stored on the client machine.

6. %ooAies: When cooie based session management is used, a toen is

generated which contains user>s information, is sent to the browser by the

server. (he cooie is sent bac to the server when the user sends a new

reuest. %y this cooie, the server is able to identify the user. #n this way the

session is maintained. &ooie is nothing but a namevalue pair, which is

stored on the client machine. %y default the cooie is implemented in most of

the browsers. #f we want then we can also disable the cooie. @or security

reasons, cooie based session management uses two types of cooies.

o *etermine +"et"er t"e Session is $e+ or ld

#n this program we are going to mae one servlet on session in which we will chec

whether the session is new or old.

(o mae this program firstly we need to mae one class named

%hecAing3heSession. #nside the 'o?et(!method, which taes two ob)ects one of

reuest and second of response. #nside this method call the method getWriter(!of

the response ob)ect. Use getSession(! of the reuest ob)ect, which returns the

8ttpSession ob)ect. =ow by using the 8ttpSessionwe can find out whether the

session is new or old.


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public class "hecLin#heSession extends HttpServlet{protected void doGet(HttpServletRequest request, HttpServletResponse response throws ServletException, !Exception { response.set"ontent#$pe(%text&ht'l%; )rintWriter p + response.etWriter(; p.println(%"hecLin hether the session is ne or old-/r%; HttpSession session + request.etSession(; if(session.isAe({ p.println(%:ou have created a ne session%; 1 else{ p.println(%Session alread$ exists%;

1 11




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#re- ./isting Session

#n this e*ample we are going to find out whether the session ispre-existingor not.

&onsider a situation where servlet want to use only a e*isting session. #t is not

always a good idea to create a new session. (o perform this wor we have one

overloaded method getSession(boolean!of the reuest ob)ect. #f we don>t want to

create a new session then we should use getSession(false!.

#n the e*ample below we have used the method getSession(false!which will test

whether the session is null or not. #f there will be no session then the new session

will be created by the method getSession(!.


PreExistingSessionServlet.ava

import java.io.*;


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import javax.servlet.*;import javax.servlet.http.*;

public class )reExistinSessionServlet extends HttpServlet{protected void doGet(HttpServletRequest request, HttpServletResponse response throws ServletException, !Exception {

response.set"ontent#$pe(%text&ht'l%; )rintWriter p + response.etWriter(; p.println(%#estin #he Session B %; HttpSession session + request.etSession(false; if(session++null{ p.println(%#here is no session%; p.println(%"an e create a session For $ou. "reatin.........%; session + request.etSession(; 1 else{ p.println(%Session alread$ exists%; 1 11




54/103

Session Last Accessed ime ./ample

(his e*ample illustrates to find current access time of session and last access time of

session. Sessions are used to maintain state and user identity across multiple page

reuests. !n implementation of 'ttpSession represents the server>s view of the

session. (he server considers a session to be new until it has been )oined by the

client. Until the client )oins the session, is=ew45 method returns true.

8ere is the source co'e of ;astccess3i"e.ava

import java.io.*;import javax.servlet.*;import javax.servlet.http.*;import java.net.*;import java.util.*;import javax.servlet.Servlet"onFi;import javax.servlet.ServletException;import javax.servlet.Servlet!utputStrea';import javax.servlet.http.HttpSession;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;

public class =astccess#i'e extends HttpServlet {public void doGet(HttpServletRequest request,HttpServletResponse response throws ServletException, !Exception {


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HttpSession session + request.etSession(true; response.set"ontent#$pe(%text&ht'l%; )rintWriter out + response.etWriter(; Strin head; nteer count + new nteer(3; if (session.isAe( { head + %Ae Session Ialue %; 1 else { head + %!ld Session value%; nteer oldcount +(nteersession.etIalue(%count%;

if (oldcount 8+ null { count + new nteer(oldcount.intIalue( D 0; 1 1 session.putIalue(%count%, count;

out.println(%-H#>=-

session was created. (he get;astccesse'3i"e(!method is used to find when last

time session was accessed by the user.

8ere is the "apping of servlet (B;astccess3i"e.avaB! in the web.x"l file:

0servlet1

0servlet-name1ast!ccess(ime0servlet-

name1

0servlet-class1ast!ccess(ime0servlet-

class1

0servlet1

0servlet-mapping1

0servlet-name1ast!ccess(ime0servlet-


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name1

0url-pattern1ast!ccess(ime0url-pattern1

0servlet-mapping1

Running the servlet by this url:

http:


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Get Session Id

#n this e*ample we are going to mae a program in which we will find the session id

which was generated by the container.

8ttpSession session C reDuest.getSession(!#nside the service method we as for

the session and every thing gets automatically, lie the creation of the 'ttpSession

ob)ect. (here is no need to generate the uniue session id. (here is no need to mae

a new &ooie ob)ect. ?verything happens automatically behind the scenes.

!s soon as call the method getSession(!of the reuest ob)ect a new ob)ect of the

session gets created by the container and a uniue session id generated to maintain

the session. (his session id is transmitted bac to the response ob)ect so that

whenever the client maes any reuest then it should also attach the session id with

the reuest ob)ect so that the container can identify the session.



public class SessiondServlet extends HttpServlet{protected void doGet(HttpServletRequest request, HttpServletResponse response throws ServletException, !Exception{ response.set"ontent#$pe(%text&ht'l%; )rintWriter p + response.etWriter(; HttpSession session + request.etSession(; Strin id + session.etd(; p.println(%Session d is B % D id; 11




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%httpB&&java.sun.co'&dtd&e/[email protected]%

-e/4app-servlet-servlet4na'eulFiqar-&servlet4na'e-servlet4classSessiondServlet-&servlet4class

-&servlet-servlet4'appin-servlet4na'eulFiqar-&servlet4na'e-url4pattern&SessiondServlet-&url4pattern-&servlet4'appin-&e/4app


*isplay session value %sing Servlet

Sometime while developing web application it is necessary to interact with the

different values of the Session ob)ect. #n this e*ample we will e*plore the different

values of the Session ob)ect and then learn how to use it in our programming code.

Bou will learn how to find all the session related information lie+

getI'.(his method is used to find the identifier of the session which is

uniue.


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is+ew.(his method is used when find, whether session is newly created or

pree*isted. #f session has never seen by user then this method return PtrueP but

if session is pree*isted then it return PfalseP.

get%reation3i"e.(his method is used to find the creation time of session. (o

use of this method we can find the following details about session i.e. day,

month, date, time, 8M(4?reenwich 9ean 3i"e5 and year will be displayed.

get;astccesse'3i"e.(his method is used to find the last accessed time of

session. #t returns the time, in milliseconds.

get9axInactiveInterval.(his method returns the total time, in seconds,

during which session remains active if user does not accesses the session for

this ma*imum time interval. !fter this time the session will be invalidated

automatically. ! negative value indicates that the session should never

timeout.

8ere is the sa"ple co'e for 8ttpSession4isplay.ava:

import java.io.*;import javax.servlet.*;import javax.servlet.http.*;import java.net.*;import java.util.*;

public class HttpSession9ispla$ extends HttpServlet

{ Strin head;

public void doGet(HttpServletRequest request, HttpServletResponse response throws ServletException, !Exception

{ HttpSession session + request.etSession(true; response.set"ontent#$pe(%text&ht'l%; )rintWriter out + response.etWriter(; nteer count + new nteer(3;


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if (session.isAe( { head + %Ae Session Ialue%; 1 else { head + %!ld Session value%; nteer oldcount +(nteersession.etIalue(%count%

if (oldcount 8+ null { count + new nteer(oldcount.intIalue( D 0; 1 1 session.putIalue(%count%, count;

out.println(%-H#>=-

%-#R

0servlet1

0servlet-name1'ttpSession$isplay0servlet-name1

0servlet-class1'ttpSession$isplay0servlet-class1

0servlet1

0servlet-mapping1

0servlet-name1'ttpSession$isplay0servlet-name1


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0url-pattern1'ttpSession$isplay0url-pattern1

0servlet-mapping1

Run this exa"ple by this url:

http:


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Hit Counter Servlet ./ample

(his e*ample illustrates about counting how many times the servlet is accessed.

When first time servlet 4%ounterServlet5 runs then session is created and value of

the counter will be 3ero and after again accessing of servlet the counter value will

be increased by one. #n this program is+ew(!method is used whether session is new

or old and get6alue(!method is used to get the value of counter.

8ere is the source co'e of %ounterServlet.ava:


public class "ounterServlet extends HttpServlet{public void doGet(HttpServletRequest request, HttpServletResponse response

throws ServletException, !Exception { HttpSession session + request.etSession(true; response.set"ontent#$pe(%text&ht'l%; )rintWriter out + response.etWriter(; nteer count + new nteer(3; Strin head; if (session.isAe( { head + %#his is the Ae Session%; 1 else {


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head + %#his is the old Session%; nteer oldcount +(nteersession.etIalue(%count%;

if (oldcount 8+ null { count + new nteer(oldcount.intIalue( D 0; 1 1 session.putIalue(%count%, count; out.println(%-H#>=-

D% -#HnFor'ation #$pe-#HSession "ountJn%D%-#RJn% D% -#9#otal Session ccessesJn% D

%-#9% D count D %Jn% D %-

9apping of Servlet (B%ounterServlet.avaB! in web.x"l file

0servlet1

0servlet-name1&ounterServlet0servlet-name1

0servlet-class1&ounterServlet0servlet-class1

0servlet1

0servlet-mapping1

0servlet-name1&ounterServlet0servlet-name1

0url-pattern1&ounterServlet0url-pattern1

0servlet-mapping1

Running the servlet by this url:

http:


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When servlet is hit two ti"es by the user the counter value will be increase' by

two as shown in figure below:

Inserting *ata In *ata0ase ta0le using Statement

#n this program we are going to insert the data in the database from our )ava program

in the table stored in the database.

(o accomplish our goal we first have to mae a class named as

ServletInserting4ata,which must e*tends the abstract 8ttpServletclass, the name

of the class should be such that other person can understand what this program is

going to perform. (he logic of the program will be written inside the 'o?et(!

method that taes two arguments, first is HttpServletRequest interface and the

second one is the HttpServletResponse interface and this method can throw

ServletException.

#nside this method call the getWriter(! method of the PrintWriterclass. We can

insert the data in the database only and only if there is a connectivity between our

database and the )ava program. (o establish the connection between our database

and the )ava program we first need to call the method for+a"e(!,which is static in

nature of the class &lass. #t taes one argument which tells about the database driver


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we are going to use. =ow use the static method get%onnection(! of the

4river9anager class. (his method taes three arguments and returns the

Connectionob)ect. SR statements are e*ecuted and results are returned within the

conte*t of a connection. =ow your connection has been established. =ow use the

method createState"ent(! of the Connectionob)ect which will return the Statement

ob)ect. (his ob)ect is used for e*ecuting a static SR statement and obtaining the

results produced by it. We have to insert values into the table so we need to write a

uery for inserting the values into the table. (his uery we will write inside the

execute@p'ate(!method of the Statement ob)ect. (his method returns int value.

#f the record will get inserted in the table then output will show Precord has been

inserted otherwise PsorryN failureP.


import java.io.*;import java.sql.*;import javax.servlet.*;import javax.servlet.http.*;

public class 9atansertion extends HttpServlet

{public void doGet(HttpServletRequest request,

HttpServletResponse response throwsServletException, !Exception{

response.set"ontent#$pe(%text&ht'l%; )rintWriter out + response.etWriter(; "onnection conn; ResultSet rs; try{ "lass.ForAa'e(%sun.jd/c.od/c.Qd/c!d/c9river%; conn + 9river>anaer.et"onnection(Ujd/cBod/cBdsn6V; State'ent state'ent + conn.createState'ent(; Strin quer$ + %nsert into ser values(sanja$X,XLrutiLX%;

int i + state'ent.executepdate(quer$; if(i8+3{ out.println(%#he record has /een inserted%;


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1 else{ out.println(%Sorr$8 ailure%; 1

rs + state'ent.executeYuer$(%select * Fro' ser%; while(rs.next({ out.println(%-p-ta/le% D rs.etStrin(0

D % % D rs.etStrin(? D %-&p -&ta/le%; 1 rs.close(; state'ent.close(; 1 catch (Exception e{ S$ste'.out.println(e; 1 1

1

web.x"l file for this progra"



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3able in the 'atabase after Insertion:

mysl1 select from empHsalT

------------------

?mp=ame salary ------------------

3ulfiar /:GGG

------------------

/ row in set 4G.G2 sec5

'etrieving *ata from t"e ta0le using Statement

#n this program we are going to fetch the data from the database in the table from

our )ava program.


Servletetching4atawhich must e*tends the abstract 8ttpServletclass, the name

of the class should be such that the other person can understand what this program is

going to perform. (he logic of the program will be written inside the 'o?et(!

method which taes two arguments, first is HttpServletRequest interface and the

second one is the HttpServletResponse interface and this method can throw

ServletException.


retrieve the data from the database only and only if there is a connectivity between


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our database and the )ava program. (o establish the connection between our

database and the )ava program we firstly need to call the method for+a"e(!which

is static in nature of the class %lass;oa'er. #t taes one argument which tells about

the database driver we are going to use. =ow use the static method get%onnection(!

of the 4river9anager class. (his method taes three arguments and returns the



method createState"ent(! of the Connectionob)ect which will return the Statement

ob)ect. (his ob)ect is used for e*ecuting a static SR statement and obtaining the

results produced by it. !s we need to retrieve the data from the table so we need to

write a uery to select all the records from the table. (his uery will be passed in the

executeFuery(! method of Statement ob)ect, which returns the ResultSet ob)ect.

=ow the data will be retrieved by using the getString(! method of the ResultSet

ob)ect.



69/103


public class Servletetchin9ataro'9ata/ase0 extends HttpServlet{public void doGet(HttpServletRequest request, HttpServletResponse response thr

ServletException, !Exception{ response.set"ontent#$pe(%text&ht'l%; )rintWriter p + response.etWriter(; Strin connectionR= + %jd/cB'$sqlB&&localhost&ulFiqar%; "onnection connection+null; try{ "lass.ForAa'e(%co'..'$sql.9river%; connection + 9river>anaer.et"onnection(connectionR=, %root%, %ad'in%; State'ent st + connection.createState'ent(; ResultSet rs + st.executeYuer$(%Select * Fro' e'pCsal%; while(rs.next({ p.println(%E'pAa'e% D % % D %E'pSalar$% D %-/r%;

p.println(rs.etStrin(0 D % % D rs.etStrin(? D %-/r%; 1 1 catch (Exception e{ p.println(e; 1 11




70/103


Inserting data from t"e H!L page to t"e data0ase

#n this program we are going to mae program in which we are going to insert the

values in the database table from the html form.

(o mae our program woring we need to mae one html form in which we will

have two fields, one is for the name and the other one is for entering the password.

!t last we will have the submit form, clicing on which the values will be passed to

the server.

(he values which we have entered in the 'tml form will be retrieved by the server

side program which we are going to write. (o accomplish our goal we first have to


------------------ ?mp=ame salary

------------------

3ulfiar /:GGG

vinod /2GGG

------------------

2 rows in set 4G.GG sec5


71/103

mae a class named as ServletInserting4ata@sing8t"lwhich must e*tends the

abstract 8ttpServletclass, the name of the class should be such that the other

person can understand what this program is going to perform. (he logic of the

program will be written inside the 'o?et(!method which taes two arguments, first

is HttpServletRequest interface and the second one is the HttpServletResponse

interface and this method can throw ServletException.


insert the data in the database only and only if there is a connectivity between our

database and the )ava program. (o establish the connection between our database

and the )ava program we firstly need to call the method for+a"e(!which is static in

nature of the class &lass. #t taes one argument which tells about the database driver

we are going to use. =ow use the static method get%onnection(! of the

4river9anager class. (his method taes three arguments and returns the



method prepareState"ent(! of the Connection ob)ect which will return the

PreparedStatementob)ect and taes one a uery which we want to fire as its input.

(he values which we have got from the html will be set in the database by using the

setString(!method of thePreparedStatementob)ect.

#f the record will get inserted in the table then output will show Precord has been

insertedP otherwise PsorryN @ailureP.


-ht'l

-head-titleAe )ae 0-&title


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-&head

-/od$

-For' 'ethod+%)!S#% action+%&n9ata


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p.println(s?; "lass.ForAa'e(%444%; connection + 9river>anaer.et"onnection(4444 ;

)reparedState'ent pst +connection.prepareState'ent(%insert into ser values(2,2%; pst.setStrin(0,s0; pst.setStrin(?,s?; int i + pst.executepdate(; if(i8+3{ p.println(%-/rRecord has /een inserted%; 1 else{ p.println(%Failed to insert the data%; 1 1 catch (Exception e{ p.println(e; 1 1

1




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3his is the output of the above input.

'etrieving data from t"e ta0le using #reparedStatement

#n this program we are going to fetch the data from the database in the table from

our )ava program using Prepare'State"ent.


Servletetching4ataro"4atabasewhich must e*tends the abstract 8ttpServlet

class, the name of the class should be such that the other person can understand what

this program is going to perform. (he logic of the program will be written inside the


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'o?et(! method which taes two arguments, first is HttpServletRequest interface

and the second one is theHttpServletResponseinterface and this method can throw

ServletException.


retrieve the data from the database only and only if there is a connectivity between

our database and the )ava program. (o establish the connection between our

database and the )ava program we firstly need to call the method for+a"e(!which

is static in nature of the class %lass;oa'er. #t taes one argument which tells about

the database driver we are going to use. =ow use the static method get%onnection(!

of the 4river9anager class. (his method taes three arguments and returns the



method prepareState"ent(! of the Connection ob)ect which will return the

PreparedStatementob)ect and taes a uery as its parameter. #n this uery we will

write the tas we want to perform. (heResultsetob)ect will be retrieved by using the

e*ecuteRuery45 method of the PreparedStatement ob)ect. =ow the data will be

retrieved by using the getString(!method of theResultSetob)ect.



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public class Servletetchin9ataro'9ata/ase extends HttpSpublic void doGet(HttpServletRequest request, HttpServle throws ServletException, !Exceptio { response.set"ontent#$pe(%text&ht'l%; )rintWriter p + response.etWriter(; Strin connectionR= + %jd/cB'$sqlB&&localhost&ulFiqar%; "onnection connection+null; try{ "lass.ForAa'e(%or.jt.''.'$sql.9river%; connection + 9river>anaer.et"onnection(connectionR=, %root%, %ad'in%; )reparedState'ent pst + connection.prepareState'ent(%Select * Fro' e'pCsal%

ResultSet rs + pst.executeYuer$(; while(rs.next({ p.println(rs.etStrin(0 D% % D rs.etStrin(?D%-/r%; 1 1 catch (Exception e{ p.println(e; 1 p.println(%hello%; 11



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3able in the 'atabase:

mysl1 select from

empHsalT

------------------ ?mp=ame salary

------------------

3ulfiar /:GGG

vinod /2GGG

------------------


Getting Columns $ames using Servlets



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import javax.servlet.*;import javax.servlet.http.*;import java.io.*;import java.sql.*;

public class ServletGettin"olu'nsAa'es extends HttpServlet{public void doGet(HttpServletRequest request, HttpServletResponse response throws ServletException, !Exception{ response.set"ontent#$pe(%text&ht'l%; )rintWriter p + response.etWriter(; Strin connectionR= + %jd/cB'$sqlB&&localhost&ulFiqar%; "onnection connection+null; try{ "lass.ForAa'e(%or.jt.''.'$sql.9river%; connection + 9river>anaer.et"onnection(connectionR=, %root%, %ad'in%; )reparedState'ent pst + connection.prepareState'ent(%select * Fro' e'pCdeta ResultSet rs + pst.executeYuer$(; ResultSet>eta9ata rs'd + rs.et>eta9ata(; int no!F"olu'ns + rs'd.et"olu'n"ount(;

&&t shos the nu'/er oF colu'ns p.println(%#he nu'/er oF colu'ns are % D no!F"olu'ns D %-/r%; &&t shos the na'e oF the colu'ns p.println(%#he na'e oF the colu'ns areB -/r%; for(int i +0; i-+no!F"olu'ns;iDD{ Strin na'es + rs'd.et"olu'nAa'e(i; p.println(na'es; 1 1 catch(Exception e{ p.println(%#he exception is % D e; 1 11

web.x"l ile for this progra":



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3able in the 'atabase:

mysl1 select from empHdetailsT

--------------------------------------

-----------------------------------

user#d =ame surname address/

address2 town country 3ipcode

--------------------------------------

----------------------------------

-


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public class ServletGettinAo!F"olu'ns extends HttpServletpublic void doGet(HttpServletRequest request, HttpServle throws ServletException, !Exception{ response.set"ontent#$pe(%text&ht'l%; )rintWriter p + response.etWriter(; Strin connectionR= + %jd/cB'$sqlB&&localhost&ulFiqar%; "onnection connection+null; try{ "lass.ForAa'e(%co'.'$sql.jd/c.9river%.nenstance(; connection + 9river>anaer.et"onnection(connectionR=, %root%, %ad'in%; )reparedState'ent pst + connection.prepareState'ent(%select * Fro' e'pCdeta ResultSet rs + pst.executeYuer$(;

ResultSet>eta9ata rs'd + rs.et>eta9ata(; int no!F"olu'ns + rs'd.et"olu'n"ount(; &&t shos the nu'/er oF colu'ns p.println(%#he nu'/er oF colu'ns are % D no!F"olu'ns; 1 catch(Exception e{ p.println(%#he exception is % D e; 1 11




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------------------------------------------------

------------------------

--

user#d =ame surname address/ address2

town country 3ipcode

------------------------------------------------

------------------------

--

;6


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public class ServletGettinAo!FRos extends HttpServlet{public void doGet(HttpServletRequest request, HttpServle throws ServletException, !Exception{ int ros+3; response.set"ontent#$pe(%text&ht'l%; )rintWriter p + response.etWriter(; Strin connectionR= + %jd/cB'$sqlB&&localhost&ulFiqar%; "onnection connection; try{ "lass.ForAa'e(%or.jt.''.'$sql.9river%; connection + 9river>anaer.et"onnection(connectionR=, %root%, %ad'in%; )reparedState'ent pst + connection.prepareState'ent(%%;

ResultSet rs + pst.executeYuer$(%select count(* Fro' e'pCsal%; while (rs.next({ ros + rs.etnt(0; 1 p.println(%#he nu'/er oF ros are % D ros; 1 catch(Exception e{ p.println(%#he exception is % D e; 1 11

web.x"l ile for this progra":



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------------------

?mp=ame salary

------------------

3ulfiar /:GGG vinod /2GGG

------------------

2 rows in set 4G.G: sec5


*eleting 'o+s from a0le


import javax.servlet.*;import javax.servlet.http.*;import java.io.*;import java.sql.*;

public class Servlet9eletinRosro'#a/le extends HttpServlet{public void doGet(HttpServletRequest request, HttpServletResponse response thr ServletException, !Exception{ int ros;

response.set"ontent#$pe(%text&ht'l%; )rintWriter p + response.etWriter(; Strin connectionR= + %jd/cB'$sqlB&&localhost&ulFiqar%; "onnection connection; try{ "lass.ForAa'e(%or.jt.''.'$sql.9river%; connection + 9river>anaer.et"onnection(connectionR=, %root%, %ad'in%; )reparedState'ent pst + connection.prepareState'ent (%delete Fro' e'pCsal here E'pAa'e + [vinod[%; int i + pst.executepdate(;


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if (i++3{ p.println(%Ro has /een deleted%; 1 else{ p.println(%Ao ros has /een deleted%; 1

1 catch(Exception e{ p.println(%#he exception is % D e; 1 11




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3able in the 'atabase after 'eletion:


------------------

?mp=ame salary

------------------

3ulfiar /:GGG

------------------

/ row in set 4G.G: sec5

*eleting All 'o+s &rom t"e data0ase a0le



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public class Servlet9eletinllRosro'#a/le extends HttpServlet{public void doGet(HttpServletRequest request, HttpServletResponse response throws ServletException, !Exception{ response.set"ontent#$pe(%text&ht'l%; )rintWriter p + response.etWriter(; Strin connectionR= + %jd/cB'$sqlB&&localhost&ulFiqar%; "onnection connection; try{ "lass.ForAa'e(%or.jt.''.'$sql.9river%; connection + 9river>anaer.et"onnection(connectionR=, %root%, %ad'in%; )reparedState'ent pst + connection.prepareState'ent(%delete Fro' e'pCsal%; int i + pst.executepdate(; if (i++3{ p.println(%ll ros are deleted%;

1 else{ p.println(%no ros has /een deleted%; 1 1 catch(Exception e{ p.println(%#he exception is % D e; 1 11




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------------------

?mp=ame salary

------------------

3ulfiar /:GGG vinod /2GGG

------------------



3able in the 'atabase after 'eletion:


?mpty set 4G.G2 sec5

Ho+ to add a column in a ta0le

&onsider a situation where the reuirement of the client gets changed and you have

ased to modify the structure of the table. #n reality it is the wor of the database

administrator but as a Java programmer you should now how you can modify thestructure of the table. (he problem is that we have to add a new column to our

database by using the )ava program. (here is no need to get panic. What we simply

need is to use a Dueryfor adding a new column in the database table.


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(o get the desired result firstly we need to mae a connection with our database.

!fter connection has been established pass the uery in the prepareState"ent(! for

adding new column in the database. (his method will return the

Prepare'State"ent ob)ect. %y the ob)ect of the Prepare'State"ent we will call

the execute@p'ate(!which will tell the status of the table.

3he co'e of the exa"ple is given below:


public class ServletddinAe"olu'n extends HttpServlet{public void doGet(HttpServletRequest request, HttpServletResponse response thr

ServletException, !Exception{ response.set"ontent#$pe(%text&ht'l%; )rintWriter p + response.etWriter(; Strin connectionR= + %jd/cB'$sqlB&&localhost&ulFiqar%; "onnection connection; try{ "lass.ForAa'e(%or.jt.''.'$sql.9river%; connection + 9river>anaer.et"onnection(connectionR=, %root%, %ad'in%; )reparedState'ent pst + connection.prepareState'ent (%alter ta/le e'pCdetails add colu'n sal int(6%; int i + pst.executepdate(; if (i++0{ p.println(%"olu'n has /een added%; 1 else{ p.println(%Ao colu'n has /een added%; 1

1 catch(Exception e{ p.println(%#he exception is % D e; 1 11



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-2x'l version+%0.3% encodin+%S!4556740%2-89!"#:)E e/4app)t mean

that you can>t send parameters to the server. %ut the total amount of characters in a

8?( is really limited. #n get method the data we send get appended to the U7 so

whatever you will send will be seen by other user so can say that it is not even

secure.


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POS3

(he "ost method is more powerful reuest. %y using "ost we can reuest as well as

send some data to the server. We use post method when we have to send a big chun

of data to the server, lie when we have to send a long enuiry form then we can

send it by using the post method.

(here are few more rarely used http methods including '?!$, "U(, (7!&?,

$??(?, C"(#C=S and &C==?&(.

Select Color

#n this program we are going to selected the various color and on the basis of the

selection the output will be displayed to the user.

(o mae this program firstly we need to mae one html page. #nside the page we

will have one select option in which we will have our colors. We will also have a

submit, clicing on which the values we have entered will be transferred to the

server.

Cn the server we will create a session. (he values which we have entered in the html

form will be retrieved by the getPara"eter6alues(!of the reDuestob)ect. #t returns

the array of String. We will chec the condition if there is any session available or

not. #f yes then we will set the attribute by using the setttribute(! method of the

8ttpSession ob)ect. (he attribute we have set will be retrieved by the get!ttribute

method of the 8ttpSessionob)ect in the ne*t page and the value will be displayed

on the browser by the PrintWriterob)ect.



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-89!"#:)E H#>= )= N.30#ransitional&&EA%-ht'l-head

-'eta http4equiv+%"ontent4#$pe% content+%text&ht'l;charset+S!4556740%-titleSelect the list oF colors-&title-&head-/od$

-For' action + %&Servlet)roject&"olor)ae%-select na'e + %colors% sie + 6 'ultiple

-option selectedGreen-&option-optionRed-&option-option:ello-&option

-option


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1

&* (non4Qava4doc* Ksee javax.servlet.http.HttpServletdoGet

(HttpServletRequest request,HttpServletResponse response*&protected void doGet(HttpServletRequest request,HttpServletResponse responsethros ServletException, !Exception {&& #!9! uto4enerated 'ethod stu/response.set"ontent#$pe(%text&ht'l%;)rintWriter p + response.etWriter(;HttpSession session + request.etSession(;

Strin colorsOP + request.et)ara'eterIalues(%colors%;iF(session8+null{session.setttri/ute(%color%,colors;session.set>axnactiventerval(T3;1p.println(%-ht'l-/od$ /color +c$an%;For(int i + 3; i-colors.lenth; iDD{p.println(%#he selected colors are% D colorsOiPD%-/r%;1p.println(%-For' action + &Servlet)roject&Get"olors%;p.println(%-input t$pe + su/'it na'e+ su/'it%;p.println(%-&For'-&/od$-&ht'l%;1

&* (non4Qava4doc* Ksee

javax.servlet.http.HttpServletdo)ost(HttpServletRequestrequest,HttpServletResponse response

*&protected void do)ost(HttpServletRequest request,HttpServletResponse responsethros ServletException, !Exception {


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&& #!9! uto4enerated 'ethod stu/11

import )ava.io.T

import )ava*.servlet.T

import )ava*.servlet.http.T

Servlet implementation class for Servlet+ 8et&olors

public class 8et&olors e*tends 'ttpServlet Y

4non-Java-doc5

Fsee )ava*.servlet.http.'ttpServletL'ttpServlet45

public 8et&olors45 Y

super45T

Z

4non-Java-doc5

Fsee )ava*.servlet.http.'ttpServletLdo8et4'ttpServlet7euest reuest, 'ttpServlet7esponse response5

protected void do8et4'ttpServlet7euest reuest, 'ttpServlet7esponse response5

throws Servlet?*ception, #C?*ception Y

(C$C !uto-generated method stub

response.set&ontent(ype4Pte*thtmlP5T

"rintWriter pw Q response.getWriter45T

'ttpSession session Q reuest.getSession4false5T

if4session QQ null5

Y

pw.println4P=o session is availableP5T

pw.println4PWe are creating a session for you. &reating.....P5T

session Q reuest.getSession45T

Z

else


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Y

String get&olors[\ Q 4String[\5session.get!ttribute4PcolorP5T

pw.println4P0html10body bgcolor Q cyan1P5T

for4int iQ GT i0get&olors.lengthTi5

Ypw.println4P(he selected colors are P get&olors[i\ P0br1P5T

Z

pw.println4P0html10body1P5T

Z

Z

4non-Java-doc5

Fsee )ava*.servlet.http.'ttpServletLdo"ost4

'ttpServlet7euest reuest, 'ttpServlet7esponse response5

protected void do"ost4'ttpServlet7euest reuest, 'ttpServlet7esponse response5

throws Servlet?*ception, #C?*ception Y


Z

Z



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send'edirect








now handle the reuest and the result will be displayed to you by the browser. (he

U7 will have the address of the new servlet. #n all this process the client is

unaware of the processing.

Servlet 7edirect forces the browser to do wor.

Send 'ed rect n ServletWhen we want that someone else should handle the response of our servlet, then

there we should use sen'Re'irect(!method.


96/103








now handle the reuest and the result will be displayed to you by the browser. #n all

this process the client is unaware of the processing.


-89!"#:)E H#>= )= N.30#ransitional&&EA%-ht'l-head-'eta http4equiv+%"ontent4#$pe% content+%text&ht'l;

charset+S!4556740%-titleRedirectin the pae-&title-&head-/od$

-For' action + %&Servlet)roject&SendRedirect%'ethod + %post%

-tr-tdEnter $our na'e B-&td-td-input t$pe + %text% na'e +

%userna'e%-&td-&tr-/r-tr

-tdEnter $our passord B-&td-td-input t$pe + %passord% na'e +

%passord%-&td-&tr-/r


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-tr-td-input t$pe + %su/'it% na'e +

%su/'it%-&td-&tr

-&For'-&/od$-&ht'l

import )ava.io.T

import )ava.io.#C?*ceptionT

import )ava*.servlet.Servlet?*ceptionT

import )ava*.servlet.http.'ttpServlet7euestT

import )ava*.servlet.http.'ttpServlet7esponseT

public class Send7edirect e*tends )ava*.servlet.http.'ttpServlet implements

)ava*.servlet.Servlet Y

public Send7edirect45 Y

super45T

Z


throws

Servlet?*ception, #C?*ception Y (C$C !uto-generated method stub

response.set&ontent(ype4Pte*thtmlP5T


String name Q reuest.get"arameter4PusernameP5T

String password Q reuest.get"arameter4PpasswordP5T

if4name.euals4PJamesP5]] password.euals4PabcP55

Y

response.send7edirect4PServlet"ro)ectValidUserP5T

Z

else

Y

pw.println4Pu r not a valid userP5T

Z

Z

Z


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import )ava.io.T

import )ava.io.#C?*ceptionT

import )ava*.servlet.Servlet?*ceptionTimport )ava*.servlet.http.'ttpServlet7euestT

import )ava*.servlet.http.'ttpServlet7esponseT

Servlet implementation class for Servlet+ ValidUser

public class ValidUser e*tends )ava*.servlet.http.'ttpServlet implements

)ava*.servlet.Servlet Y

4non-Java-doc5 Fsee )ava*.servlet.http.'ttpServletL'ttpServlet45

public ValidUser45 Y

super45T

Z

4non-Java-doc5

Fsee )ava*.servlet.http.'ttpServletLdo8et4'ttpServlet7euest reuest,

'ttpServlet7esponse response5

protected void do8et4'ttpServlet7euest reuest, 'ttpServlet7esponse response5

throws

Servlet?*ception, #C?*ception Y


Z

4non-Java-doc5

Fsee )ava*.servlet.http.'ttpServletLdo"ost4'ttpServlet7euest reuest,'ttpServlet7esponse response5


throws

Servlet?*ception, #C?*ception Y


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pw.println4PWelcome to roseindia.net0br1P5T

pw.println4Phow are youP5T

ZZ


Servlet Conte/t


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ServletContext is a interface which helps us to communicate with the servlet

container. (here is only one Servlet&onte*t for the entire web application and the

components of the web application can share it. (he information in the

Servlet&onte*t will be common to all the components. 7emember that each servlet

will have its own Servlet%onfig. (he Servet&onte*t is created by the container

when the web application is deployed and after that only the conte*t is available to

each servlet in the web application.

Web application initialiGation:

/. @irst of all the web container reads the deployment descriptor file and thencreates a namevalue pair for each 0conte*t-param1 tag.

2. !fter creating the namevalue pair it creates a new instance of Servlet&onte*t.

6. #ts the responsibility of the &ontainer to give the reference of the

Servlet&onte*t to the conte*t init parameters.

9. (he servlet and )sp which are part of the same web application can have the

access of the Servlet&onte*t.

(he &onte*t init parameters are available to the entire web application not )ust to the

single servlet lie servlet init parameters.

'ow can we do the mapping of the &onte*t init parameters in web.*ml

Hservlet

Hservlet*na"e9appingH


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Hpara"*na"eE"ailH


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get%reation3i"e(!: get&reation(ime45 is a method. (his is the method that returns

the time when this session was created a long integer time.

get;astccesse'3i"e(!: getast!ccessed(ime45 is a method. (his is the method

that returns the last time the client sends reuest with this session.

getI'(!: (his is the method that returns a string containing the uniue identifier

assigned to this session.

8ere is the co'e of this progra":

import java.io.*;import java.util.*;import javax.servlet.*;import javax.servlet.http.*;

public class ccessed9ateServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response

throws ServletException, !Exception { )rintWriter p + response.etWriter(;

HttpSession session + request.etSession(true;9ate create + new 9ate(session.et"reation#i'e(;9ate accessed + new 9ate(session.et=astccessed#i'e(;p.println(%9 % D session.etd(;

p.println(%"reateB % D create;p.println(%=ast

servlet notes.doc

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