Servlet

Outline

bull Introduction

bull Interface Servlet and the Servlet Life Cycle

bull HttpServlet Class

bull HttpServletRequest Interface

bull HttpServletResponse Interface

bull Handling HTTP get Requests

bull Deploying a Web Application

bull Handling HTTP get Requests Containing Data

bull Handling HTTP post Requests

bull Redirecting Requests to Other Resources

bull Multi-Tier Applications Using JDBC from a Servlet

Server-side Java for the web

bull a servlet is a Java program which outputs an html page it is

a server-side technology

browser web server

HTTP Request

HTTP Response

Server-side Request

Response Header +

Html file

Java Servlet

Java Server Page

servlet container

(engine) -

Tomcat

Introduction

bull 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

bull Although servlets can respond to any type of request they

are commonly used to extend the applications hosted by

web servers For such applications Java Servlet

technology defines HTTP-specific servlet classes

Introduction

bull The javaxservlet and javaxservlethttp packages provide

interfaces and classes for writing servlets

bull All servlets must implement the Servlet interface which

defines life-cycle methods

bull When implementing a generic service you can use or extend

the GenericServlet class provided with the Java Servlet API

bull The HttpServlet class provides methods such

as doGet and doPost for handling HTTP-specific services

Working of Servlet

bull Client sends HTTP request

bull Servlet container receives request directs it to the

appropriate servlet

bull Servlet does processing (including interacting with

databases)

bull Servlet returns results to client in form of HTML

document

Structure of Web Modules

Interface Servlet

bull Interface Servlet

ndash All servlets must implement this interface

ndash All methods of interface Servlet are invoked by servlet

container

bull Servlet implementation (two abstract classes

implement Servlet interface)

ndash GenericServlet (javaxservlet)

ndash HttpServlet (javaxservlethttp)

ndash service method

public void service(ServletRequest req ServletResponse res)

bull ServletRequest object is data from client

bull ServletResponse object is data to the client

Servlet Life Cycle

bull The life cycle of a servlet is controlled by the container in

which the servlet has been deployed

bull When a request is mapped to a servlet the container

performs the following steps

bull If an instance of the servlet does not exist the web container

ndash Loads the servlet class

ndash Creates an instance of the servlet class

ndash Initializes the servlet instance by calling the init method

Servlet Life Cycle

ndash Servletrsquos service method handles requests (receives

processes sends response to client)

ndash Servletrsquos service method called once per request runs in

a Thread

ndash Servletrsquos destroy method releases servlet resources when

the servlet container terminates the servlet

Interface Servlet and the Servlet Life Cycle

Method Description void init( ServletConfig config )

The servlet container calls this method once during a servletrsquos execution cycle to initialize the

servlet The ServletConfig argument is supplied by the servlet container that executes the

servlet ServletConfig getServletConfig()

This method returns a reference to an object that implements interface ServletConfig This

object provides access to the servletrsquos configuration information such as servlet initialization

parameters and the servletrsquos ServletContext which provides the servlet with access to its

environment (ie the servlet container in which the servlet executes)

String getServletInfo()

This method is defined by a servlet programmer to return a string containing servlet information

such as the servletrsquos author and version void service( ServletRequest request ServletResponse response )

The servlet container calls this method to respond to a client request to the servlet

void destroy()

This ldquocleanuprdquo method is called when a servlet is terminated by its servlet container Resources

used by the servlet such as an open file or an open database connection should be deallocated here

Methods of interface Servlet (package javaxservlet)

HttpServlet Class

bull Web-based servlets typically extend HttpServlet

class

bull HttpServlet overrides method service

bull Two most common HTTP request types

ndash get requests (data rides on URL)

ndash post requests (data sent in a file)

bull Method doGet responds to get requests

public void doGet(HttpServletRequest request

HttpServletResponse response)

bull Method doPost responds to post requests

public void doPost(HttpServletRequest request

HttpServletResponse response)

HttpServlet Class

bull HttpServletRequest and

HttpServletResponse objects enable

interaction between client and server

HttpServletRequest Interface

bull Web server

ndash creates an HttpServletRequest object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

ndash HttpServletRequest object contains the request from

the client

HttpServletRequest Interface

Method Description String getParameter( String name )

Obtains the value of a parameter sent to the servlet as part of a get or post request The

name argument represents the parameter name Enumeration getParameterNames()

Returns the names of all the parameters sent to the servlet as part of a post request

String[] getParameterValues( String name )

For a parameter with multiple values this method returns an array of strings containing the

values for a specified servlet parameter Cookie[] getCookies()

Returns an array of Cookie objects stored on the client by the server Cookie objects can

be used to uniquely identify clients to the servlet HttpSession getSession( boolean create )

Returns an HttpSession object associated with the clientrsquos current browsing session

This method can create an HttpSession object (true argument) if one does not already

exist for the client HttpSession objects are used in similar ways to Cookies for

uniquely identifying clients

Fig 243 Some methods of interface HttpServletRequest

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

Outline

bull Introduction

bull Interface Servlet and the Servlet Life Cycle

bull HttpServlet Class

bull HttpServletRequest Interface

bull HttpServletResponse Interface

bull Handling HTTP get Requests

bull Deploying a Web Application

bull Handling HTTP get Requests Containing Data

bull Handling HTTP post Requests

bull Redirecting Requests to Other Resources

bull Multi-Tier Applications Using JDBC from a Servlet

Server-side Java for the web

bull a servlet is a Java program which outputs an html page it is

a server-side technology

browser web server

HTTP Request

HTTP Response

Server-side Request

Response Header +

Html file

Java Servlet

Java Server Page

servlet container

(engine) -

Tomcat

Introduction

bull 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

bull Although servlets can respond to any type of request they

are commonly used to extend the applications hosted by

web servers For such applications Java Servlet

technology defines HTTP-specific servlet classes

Introduction

bull The javaxservlet and javaxservlethttp packages provide

interfaces and classes for writing servlets

bull All servlets must implement the Servlet interface which

defines life-cycle methods

bull When implementing a generic service you can use or extend

the GenericServlet class provided with the Java Servlet API

bull The HttpServlet class provides methods such

as doGet and doPost for handling HTTP-specific services

Working of Servlet

bull Client sends HTTP request

bull Servlet container receives request directs it to the

appropriate servlet

bull Servlet does processing (including interacting with

databases)

bull Servlet returns results to client in form of HTML

document

Structure of Web Modules

Interface Servlet

bull Interface Servlet

ndash All servlets must implement this interface

ndash All methods of interface Servlet are invoked by servlet

container

bull Servlet implementation (two abstract classes

implement Servlet interface)

ndash GenericServlet (javaxservlet)

ndash HttpServlet (javaxservlethttp)

ndash service method

public void service(ServletRequest req ServletResponse res)

bull ServletRequest object is data from client

bull ServletResponse object is data to the client

Servlet Life Cycle

bull The life cycle of a servlet is controlled by the container in

which the servlet has been deployed

bull When a request is mapped to a servlet the container

performs the following steps

bull If an instance of the servlet does not exist the web container

ndash Loads the servlet class

ndash Creates an instance of the servlet class

ndash Initializes the servlet instance by calling the init method

Servlet Life Cycle

ndash Servletrsquos service method handles requests (receives

processes sends response to client)

ndash Servletrsquos service method called once per request runs in

a Thread

ndash Servletrsquos destroy method releases servlet resources when

the servlet container terminates the servlet

Interface Servlet and the Servlet Life Cycle

Method Description void init( ServletConfig config )

The servlet container calls this method once during a servletrsquos execution cycle to initialize the

servlet The ServletConfig argument is supplied by the servlet container that executes the

servlet ServletConfig getServletConfig()

This method returns a reference to an object that implements interface ServletConfig This

object provides access to the servletrsquos configuration information such as servlet initialization

parameters and the servletrsquos ServletContext which provides the servlet with access to its

environment (ie the servlet container in which the servlet executes)

String getServletInfo()

This method is defined by a servlet programmer to return a string containing servlet information

such as the servletrsquos author and version void service( ServletRequest request ServletResponse response )

The servlet container calls this method to respond to a client request to the servlet

void destroy()

This ldquocleanuprdquo method is called when a servlet is terminated by its servlet container Resources

used by the servlet such as an open file or an open database connection should be deallocated here

Methods of interface Servlet (package javaxservlet)

HttpServlet Class

bull Web-based servlets typically extend HttpServlet

class

bull HttpServlet overrides method service

bull Two most common HTTP request types

ndash get requests (data rides on URL)

ndash post requests (data sent in a file)

bull Method doGet responds to get requests

public void doGet(HttpServletRequest request

HttpServletResponse response)

bull Method doPost responds to post requests

public void doPost(HttpServletRequest request

HttpServletResponse response)

HttpServlet Class

bull HttpServletRequest and

HttpServletResponse objects enable

interaction between client and server

HttpServletRequest Interface

bull Web server

ndash creates an HttpServletRequest object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

ndash HttpServletRequest object contains the request from

the client

HttpServletRequest Interface

Method Description String getParameter( String name )

Obtains the value of a parameter sent to the servlet as part of a get or post request The

name argument represents the parameter name Enumeration getParameterNames()

Returns the names of all the parameters sent to the servlet as part of a post request

String[] getParameterValues( String name )

For a parameter with multiple values this method returns an array of strings containing the

values for a specified servlet parameter Cookie[] getCookies()

Returns an array of Cookie objects stored on the client by the server Cookie objects can

be used to uniquely identify clients to the servlet HttpSession getSession( boolean create )

Returns an HttpSession object associated with the clientrsquos current browsing session

This method can create an HttpSession object (true argument) if one does not already

exist for the client HttpSession objects are used in similar ways to Cookies for

uniquely identifying clients

Fig 243 Some methods of interface HttpServletRequest

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

Server-side Java for the web

bull a servlet is a Java program which outputs an html page it is

a server-side technology

browser web server

HTTP Request

HTTP Response

Server-side Request

Response Header +

Html file

Java Servlet

Java Server Page

servlet container

(engine) -

Tomcat

Introduction

bull 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

bull Although servlets can respond to any type of request they

are commonly used to extend the applications hosted by

web servers For such applications Java Servlet

technology defines HTTP-specific servlet classes

Introduction

bull The javaxservlet and javaxservlethttp packages provide

interfaces and classes for writing servlets

bull All servlets must implement the Servlet interface which

defines life-cycle methods

bull When implementing a generic service you can use or extend

the GenericServlet class provided with the Java Servlet API

bull The HttpServlet class provides methods such

as doGet and doPost for handling HTTP-specific services

Working of Servlet

bull Client sends HTTP request

bull Servlet container receives request directs it to the

appropriate servlet

bull Servlet does processing (including interacting with

databases)

bull Servlet returns results to client in form of HTML

document

Structure of Web Modules

Interface Servlet

bull Interface Servlet

ndash All servlets must implement this interface

ndash All methods of interface Servlet are invoked by servlet

container

bull Servlet implementation (two abstract classes

implement Servlet interface)

ndash GenericServlet (javaxservlet)

ndash HttpServlet (javaxservlethttp)

ndash service method

public void service(ServletRequest req ServletResponse res)

bull ServletRequest object is data from client

bull ServletResponse object is data to the client

Servlet Life Cycle

bull The life cycle of a servlet is controlled by the container in

which the servlet has been deployed

bull When a request is mapped to a servlet the container

performs the following steps

bull If an instance of the servlet does not exist the web container

ndash Loads the servlet class

ndash Creates an instance of the servlet class

ndash Initializes the servlet instance by calling the init method

Servlet Life Cycle

ndash Servletrsquos service method handles requests (receives

processes sends response to client)

ndash Servletrsquos service method called once per request runs in

a Thread

ndash Servletrsquos destroy method releases servlet resources when

the servlet container terminates the servlet

Interface Servlet and the Servlet Life Cycle

Method Description void init( ServletConfig config )

The servlet container calls this method once during a servletrsquos execution cycle to initialize the

servlet The ServletConfig argument is supplied by the servlet container that executes the

servlet ServletConfig getServletConfig()

This method returns a reference to an object that implements interface ServletConfig This

object provides access to the servletrsquos configuration information such as servlet initialization

parameters and the servletrsquos ServletContext which provides the servlet with access to its

environment (ie the servlet container in which the servlet executes)

String getServletInfo()

This method is defined by a servlet programmer to return a string containing servlet information

such as the servletrsquos author and version void service( ServletRequest request ServletResponse response )

The servlet container calls this method to respond to a client request to the servlet

void destroy()

This ldquocleanuprdquo method is called when a servlet is terminated by its servlet container Resources

used by the servlet such as an open file or an open database connection should be deallocated here

Methods of interface Servlet (package javaxservlet)

HttpServlet Class

bull Web-based servlets typically extend HttpServlet

class

bull HttpServlet overrides method service

bull Two most common HTTP request types

ndash get requests (data rides on URL)

ndash post requests (data sent in a file)

bull Method doGet responds to get requests

public void doGet(HttpServletRequest request

HttpServletResponse response)

bull Method doPost responds to post requests

public void doPost(HttpServletRequest request

HttpServletResponse response)

HttpServlet Class

bull HttpServletRequest and

HttpServletResponse objects enable

interaction between client and server

HttpServletRequest Interface

bull Web server

ndash creates an HttpServletRequest object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

ndash HttpServletRequest object contains the request from

the client

HttpServletRequest Interface

Method Description String getParameter( String name )

Obtains the value of a parameter sent to the servlet as part of a get or post request The

name argument represents the parameter name Enumeration getParameterNames()

Returns the names of all the parameters sent to the servlet as part of a post request

String[] getParameterValues( String name )

For a parameter with multiple values this method returns an array of strings containing the

values for a specified servlet parameter Cookie[] getCookies()

Returns an array of Cookie objects stored on the client by the server Cookie objects can

be used to uniquely identify clients to the servlet HttpSession getSession( boolean create )

Returns an HttpSession object associated with the clientrsquos current browsing session

This method can create an HttpSession object (true argument) if one does not already

exist for the client HttpSession objects are used in similar ways to Cookies for

uniquely identifying clients

Fig 243 Some methods of interface HttpServletRequest

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

Introduction

bull 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

bull Although servlets can respond to any type of request they

are commonly used to extend the applications hosted by

web servers For such applications Java Servlet

technology defines HTTP-specific servlet classes

Introduction

bull The javaxservlet and javaxservlethttp packages provide

interfaces and classes for writing servlets

bull All servlets must implement the Servlet interface which

defines life-cycle methods

bull When implementing a generic service you can use or extend

the GenericServlet class provided with the Java Servlet API

bull The HttpServlet class provides methods such

as doGet and doPost for handling HTTP-specific services

Working of Servlet

bull Client sends HTTP request

bull Servlet container receives request directs it to the

appropriate servlet

bull Servlet does processing (including interacting with

databases)

bull Servlet returns results to client in form of HTML

document

Structure of Web Modules

Interface Servlet

bull Interface Servlet

ndash All servlets must implement this interface

ndash All methods of interface Servlet are invoked by servlet

container

bull Servlet implementation (two abstract classes

implement Servlet interface)

ndash GenericServlet (javaxservlet)

ndash HttpServlet (javaxservlethttp)

ndash service method

public void service(ServletRequest req ServletResponse res)

bull ServletRequest object is data from client

bull ServletResponse object is data to the client

Servlet Life Cycle

bull The life cycle of a servlet is controlled by the container in

which the servlet has been deployed

bull When a request is mapped to a servlet the container

performs the following steps

bull If an instance of the servlet does not exist the web container

ndash Loads the servlet class

ndash Creates an instance of the servlet class

ndash Initializes the servlet instance by calling the init method

Servlet Life Cycle

ndash Servletrsquos service method handles requests (receives

processes sends response to client)

ndash Servletrsquos service method called once per request runs in

a Thread

ndash Servletrsquos destroy method releases servlet resources when

the servlet container terminates the servlet

Interface Servlet and the Servlet Life Cycle

Method Description void init( ServletConfig config )

The servlet container calls this method once during a servletrsquos execution cycle to initialize the

servlet The ServletConfig argument is supplied by the servlet container that executes the

servlet ServletConfig getServletConfig()

This method returns a reference to an object that implements interface ServletConfig This

object provides access to the servletrsquos configuration information such as servlet initialization

parameters and the servletrsquos ServletContext which provides the servlet with access to its

environment (ie the servlet container in which the servlet executes)

String getServletInfo()

This method is defined by a servlet programmer to return a string containing servlet information

such as the servletrsquos author and version void service( ServletRequest request ServletResponse response )

The servlet container calls this method to respond to a client request to the servlet

void destroy()

This ldquocleanuprdquo method is called when a servlet is terminated by its servlet container Resources

used by the servlet such as an open file or an open database connection should be deallocated here

Methods of interface Servlet (package javaxservlet)

HttpServlet Class

bull Web-based servlets typically extend HttpServlet

class

bull HttpServlet overrides method service

bull Two most common HTTP request types

ndash get requests (data rides on URL)

ndash post requests (data sent in a file)

bull Method doGet responds to get requests

public void doGet(HttpServletRequest request

HttpServletResponse response)

bull Method doPost responds to post requests

public void doPost(HttpServletRequest request

HttpServletResponse response)

HttpServlet Class

bull HttpServletRequest and

HttpServletResponse objects enable

interaction between client and server

HttpServletRequest Interface

bull Web server

ndash creates an HttpServletRequest object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

ndash HttpServletRequest object contains the request from

the client

HttpServletRequest Interface

Method Description String getParameter( String name )

Obtains the value of a parameter sent to the servlet as part of a get or post request The

name argument represents the parameter name Enumeration getParameterNames()

Returns the names of all the parameters sent to the servlet as part of a post request

String[] getParameterValues( String name )

For a parameter with multiple values this method returns an array of strings containing the

values for a specified servlet parameter Cookie[] getCookies()

Returns an array of Cookie objects stored on the client by the server Cookie objects can

be used to uniquely identify clients to the servlet HttpSession getSession( boolean create )

Returns an HttpSession object associated with the clientrsquos current browsing session

This method can create an HttpSession object (true argument) if one does not already

exist for the client HttpSession objects are used in similar ways to Cookies for

uniquely identifying clients

Fig 243 Some methods of interface HttpServletRequest

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

Introduction

bull The javaxservlet and javaxservlethttp packages provide

interfaces and classes for writing servlets

bull All servlets must implement the Servlet interface which

defines life-cycle methods

bull When implementing a generic service you can use or extend

the GenericServlet class provided with the Java Servlet API

bull The HttpServlet class provides methods such

as doGet and doPost for handling HTTP-specific services

Working of Servlet

bull Client sends HTTP request

bull Servlet container receives request directs it to the

appropriate servlet

bull Servlet does processing (including interacting with

databases)

bull Servlet returns results to client in form of HTML

document

Structure of Web Modules

Interface Servlet

bull Interface Servlet

ndash All servlets must implement this interface

ndash All methods of interface Servlet are invoked by servlet

container

bull Servlet implementation (two abstract classes

implement Servlet interface)

ndash GenericServlet (javaxservlet)

ndash HttpServlet (javaxservlethttp)

ndash service method

public void service(ServletRequest req ServletResponse res)

bull ServletRequest object is data from client

bull ServletResponse object is data to the client

Servlet Life Cycle

bull The life cycle of a servlet is controlled by the container in

which the servlet has been deployed

bull When a request is mapped to a servlet the container

performs the following steps

bull If an instance of the servlet does not exist the web container

ndash Loads the servlet class

ndash Creates an instance of the servlet class

ndash Initializes the servlet instance by calling the init method

Servlet Life Cycle

ndash Servletrsquos service method handles requests (receives

processes sends response to client)

ndash Servletrsquos service method called once per request runs in

a Thread

ndash Servletrsquos destroy method releases servlet resources when

the servlet container terminates the servlet

Interface Servlet and the Servlet Life Cycle

Method Description void init( ServletConfig config )

The servlet container calls this method once during a servletrsquos execution cycle to initialize the

servlet The ServletConfig argument is supplied by the servlet container that executes the

servlet ServletConfig getServletConfig()

This method returns a reference to an object that implements interface ServletConfig This

object provides access to the servletrsquos configuration information such as servlet initialization

parameters and the servletrsquos ServletContext which provides the servlet with access to its

environment (ie the servlet container in which the servlet executes)

String getServletInfo()

This method is defined by a servlet programmer to return a string containing servlet information

such as the servletrsquos author and version void service( ServletRequest request ServletResponse response )

The servlet container calls this method to respond to a client request to the servlet

void destroy()

This ldquocleanuprdquo method is called when a servlet is terminated by its servlet container Resources

used by the servlet such as an open file or an open database connection should be deallocated here

Methods of interface Servlet (package javaxservlet)

HttpServlet Class

bull Web-based servlets typically extend HttpServlet

class

bull HttpServlet overrides method service

bull Two most common HTTP request types

ndash get requests (data rides on URL)

ndash post requests (data sent in a file)

bull Method doGet responds to get requests

public void doGet(HttpServletRequest request

HttpServletResponse response)

bull Method doPost responds to post requests

public void doPost(HttpServletRequest request

HttpServletResponse response)

HttpServlet Class

bull HttpServletRequest and

HttpServletResponse objects enable

interaction between client and server

HttpServletRequest Interface

bull Web server

ndash creates an HttpServletRequest object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

ndash HttpServletRequest object contains the request from

the client

HttpServletRequest Interface

Method Description String getParameter( String name )

Obtains the value of a parameter sent to the servlet as part of a get or post request The

name argument represents the parameter name Enumeration getParameterNames()

Returns the names of all the parameters sent to the servlet as part of a post request

String[] getParameterValues( String name )

For a parameter with multiple values this method returns an array of strings containing the

values for a specified servlet parameter Cookie[] getCookies()

Returns an array of Cookie objects stored on the client by the server Cookie objects can

be used to uniquely identify clients to the servlet HttpSession getSession( boolean create )

Returns an HttpSession object associated with the clientrsquos current browsing session

This method can create an HttpSession object (true argument) if one does not already

exist for the client HttpSession objects are used in similar ways to Cookies for

uniquely identifying clients

Fig 243 Some methods of interface HttpServletRequest

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

Working of Servlet

bull Client sends HTTP request

bull Servlet container receives request directs it to the

appropriate servlet

bull Servlet does processing (including interacting with

databases)

bull Servlet returns results to client in form of HTML

document

Structure of Web Modules

Interface Servlet

bull Interface Servlet

ndash All servlets must implement this interface

ndash All methods of interface Servlet are invoked by servlet

container

bull Servlet implementation (two abstract classes

implement Servlet interface)

ndash GenericServlet (javaxservlet)

ndash HttpServlet (javaxservlethttp)

ndash service method

public void service(ServletRequest req ServletResponse res)

bull ServletRequest object is data from client

bull ServletResponse object is data to the client

Servlet Life Cycle

bull The life cycle of a servlet is controlled by the container in

which the servlet has been deployed

bull When a request is mapped to a servlet the container

performs the following steps

bull If an instance of the servlet does not exist the web container

ndash Loads the servlet class

ndash Creates an instance of the servlet class

ndash Initializes the servlet instance by calling the init method

Servlet Life Cycle

ndash Servletrsquos service method handles requests (receives

processes sends response to client)

ndash Servletrsquos service method called once per request runs in

a Thread

ndash Servletrsquos destroy method releases servlet resources when

the servlet container terminates the servlet

Interface Servlet and the Servlet Life Cycle

Method Description void init( ServletConfig config )

The servlet container calls this method once during a servletrsquos execution cycle to initialize the

servlet The ServletConfig argument is supplied by the servlet container that executes the

servlet ServletConfig getServletConfig()

This method returns a reference to an object that implements interface ServletConfig This

object provides access to the servletrsquos configuration information such as servlet initialization

parameters and the servletrsquos ServletContext which provides the servlet with access to its

environment (ie the servlet container in which the servlet executes)

String getServletInfo()

This method is defined by a servlet programmer to return a string containing servlet information

such as the servletrsquos author and version void service( ServletRequest request ServletResponse response )

The servlet container calls this method to respond to a client request to the servlet

void destroy()

This ldquocleanuprdquo method is called when a servlet is terminated by its servlet container Resources

used by the servlet such as an open file or an open database connection should be deallocated here

Methods of interface Servlet (package javaxservlet)

HttpServlet Class

bull Web-based servlets typically extend HttpServlet

class

bull HttpServlet overrides method service

bull Two most common HTTP request types

ndash get requests (data rides on URL)

ndash post requests (data sent in a file)

bull Method doGet responds to get requests

public void doGet(HttpServletRequest request

HttpServletResponse response)

bull Method doPost responds to post requests

public void doPost(HttpServletRequest request

HttpServletResponse response)

HttpServlet Class

bull HttpServletRequest and

HttpServletResponse objects enable

interaction between client and server

HttpServletRequest Interface

bull Web server

ndash creates an HttpServletRequest object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

ndash HttpServletRequest object contains the request from

the client

HttpServletRequest Interface

Method Description String getParameter( String name )

Obtains the value of a parameter sent to the servlet as part of a get or post request The

name argument represents the parameter name Enumeration getParameterNames()

Returns the names of all the parameters sent to the servlet as part of a post request

String[] getParameterValues( String name )

For a parameter with multiple values this method returns an array of strings containing the

values for a specified servlet parameter Cookie[] getCookies()

Returns an array of Cookie objects stored on the client by the server Cookie objects can

be used to uniquely identify clients to the servlet HttpSession getSession( boolean create )

Returns an HttpSession object associated with the clientrsquos current browsing session

This method can create an HttpSession object (true argument) if one does not already

exist for the client HttpSession objects are used in similar ways to Cookies for

uniquely identifying clients

Fig 243 Some methods of interface HttpServletRequest

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

Structure of Web Modules

Interface Servlet

bull Interface Servlet

ndash All servlets must implement this interface

ndash All methods of interface Servlet are invoked by servlet

container

bull Servlet implementation (two abstract classes

implement Servlet interface)

ndash GenericServlet (javaxservlet)

ndash HttpServlet (javaxservlethttp)

ndash service method

public void service(ServletRequest req ServletResponse res)

bull ServletRequest object is data from client

bull ServletResponse object is data to the client

Servlet Life Cycle

bull The life cycle of a servlet is controlled by the container in

which the servlet has been deployed

bull When a request is mapped to a servlet the container

performs the following steps

bull If an instance of the servlet does not exist the web container

ndash Loads the servlet class

ndash Creates an instance of the servlet class

ndash Initializes the servlet instance by calling the init method

Servlet Life Cycle

ndash Servletrsquos service method handles requests (receives

processes sends response to client)

ndash Servletrsquos service method called once per request runs in

a Thread

ndash Servletrsquos destroy method releases servlet resources when

the servlet container terminates the servlet

Interface Servlet and the Servlet Life Cycle

Method Description void init( ServletConfig config )

The servlet container calls this method once during a servletrsquos execution cycle to initialize the

servlet The ServletConfig argument is supplied by the servlet container that executes the

servlet ServletConfig getServletConfig()

This method returns a reference to an object that implements interface ServletConfig This

object provides access to the servletrsquos configuration information such as servlet initialization

parameters and the servletrsquos ServletContext which provides the servlet with access to its

environment (ie the servlet container in which the servlet executes)

String getServletInfo()

This method is defined by a servlet programmer to return a string containing servlet information

such as the servletrsquos author and version void service( ServletRequest request ServletResponse response )

The servlet container calls this method to respond to a client request to the servlet

void destroy()

This ldquocleanuprdquo method is called when a servlet is terminated by its servlet container Resources

used by the servlet such as an open file or an open database connection should be deallocated here

Methods of interface Servlet (package javaxservlet)

HttpServlet Class

bull Web-based servlets typically extend HttpServlet

class

bull HttpServlet overrides method service

bull Two most common HTTP request types

ndash get requests (data rides on URL)

ndash post requests (data sent in a file)

bull Method doGet responds to get requests

public void doGet(HttpServletRequest request

HttpServletResponse response)

bull Method doPost responds to post requests

public void doPost(HttpServletRequest request

HttpServletResponse response)

HttpServlet Class

bull HttpServletRequest and

HttpServletResponse objects enable

interaction between client and server

HttpServletRequest Interface

bull Web server

ndash creates an HttpServletRequest object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

ndash HttpServletRequest object contains the request from

the client

HttpServletRequest Interface

Method Description String getParameter( String name )

Obtains the value of a parameter sent to the servlet as part of a get or post request The

name argument represents the parameter name Enumeration getParameterNames()

Returns the names of all the parameters sent to the servlet as part of a post request

String[] getParameterValues( String name )

For a parameter with multiple values this method returns an array of strings containing the

values for a specified servlet parameter Cookie[] getCookies()

Returns an array of Cookie objects stored on the client by the server Cookie objects can

be used to uniquely identify clients to the servlet HttpSession getSession( boolean create )

Returns an HttpSession object associated with the clientrsquos current browsing session

This method can create an HttpSession object (true argument) if one does not already

exist for the client HttpSession objects are used in similar ways to Cookies for

uniquely identifying clients

Fig 243 Some methods of interface HttpServletRequest

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

Interface Servlet

bull Interface Servlet

ndash All servlets must implement this interface

ndash All methods of interface Servlet are invoked by servlet

container

bull Servlet implementation (two abstract classes

implement Servlet interface)

ndash GenericServlet (javaxservlet)

ndash HttpServlet (javaxservlethttp)

ndash service method

public void service(ServletRequest req ServletResponse res)

bull ServletRequest object is data from client

bull ServletResponse object is data to the client

Servlet Life Cycle

bull The life cycle of a servlet is controlled by the container in

which the servlet has been deployed

bull When a request is mapped to a servlet the container

performs the following steps

bull If an instance of the servlet does not exist the web container

ndash Loads the servlet class

ndash Creates an instance of the servlet class

ndash Initializes the servlet instance by calling the init method

Servlet Life Cycle

ndash Servletrsquos service method handles requests (receives

processes sends response to client)

ndash Servletrsquos service method called once per request runs in

a Thread

ndash Servletrsquos destroy method releases servlet resources when

the servlet container terminates the servlet

Interface Servlet and the Servlet Life Cycle

Method Description void init( ServletConfig config )

The servlet container calls this method once during a servletrsquos execution cycle to initialize the

servlet The ServletConfig argument is supplied by the servlet container that executes the

servlet ServletConfig getServletConfig()

This method returns a reference to an object that implements interface ServletConfig This

object provides access to the servletrsquos configuration information such as servlet initialization

parameters and the servletrsquos ServletContext which provides the servlet with access to its

environment (ie the servlet container in which the servlet executes)

String getServletInfo()

This method is defined by a servlet programmer to return a string containing servlet information

such as the servletrsquos author and version void service( ServletRequest request ServletResponse response )

The servlet container calls this method to respond to a client request to the servlet

void destroy()

This ldquocleanuprdquo method is called when a servlet is terminated by its servlet container Resources

used by the servlet such as an open file or an open database connection should be deallocated here

Methods of interface Servlet (package javaxservlet)

HttpServlet Class

bull Web-based servlets typically extend HttpServlet

class

bull HttpServlet overrides method service

bull Two most common HTTP request types

ndash get requests (data rides on URL)

ndash post requests (data sent in a file)

bull Method doGet responds to get requests

public void doGet(HttpServletRequest request

HttpServletResponse response)

bull Method doPost responds to post requests

public void doPost(HttpServletRequest request

HttpServletResponse response)

HttpServlet Class

bull HttpServletRequest and

HttpServletResponse objects enable

interaction between client and server

HttpServletRequest Interface

bull Web server

ndash creates an HttpServletRequest object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

ndash HttpServletRequest object contains the request from

the client

HttpServletRequest Interface

Method Description String getParameter( String name )

Obtains the value of a parameter sent to the servlet as part of a get or post request The

name argument represents the parameter name Enumeration getParameterNames()

Returns the names of all the parameters sent to the servlet as part of a post request

String[] getParameterValues( String name )

For a parameter with multiple values this method returns an array of strings containing the

values for a specified servlet parameter Cookie[] getCookies()

Returns an array of Cookie objects stored on the client by the server Cookie objects can

be used to uniquely identify clients to the servlet HttpSession getSession( boolean create )

Returns an HttpSession object associated with the clientrsquos current browsing session

This method can create an HttpSession object (true argument) if one does not already

exist for the client HttpSession objects are used in similar ways to Cookies for

uniquely identifying clients

Fig 243 Some methods of interface HttpServletRequest

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

Servlet Life Cycle

bull The life cycle of a servlet is controlled by the container in

which the servlet has been deployed

bull When a request is mapped to a servlet the container

performs the following steps

bull If an instance of the servlet does not exist the web container

ndash Loads the servlet class

ndash Creates an instance of the servlet class

ndash Initializes the servlet instance by calling the init method

Servlet Life Cycle

ndash Servletrsquos service method handles requests (receives

processes sends response to client)

ndash Servletrsquos service method called once per request runs in

a Thread

ndash Servletrsquos destroy method releases servlet resources when

the servlet container terminates the servlet

Interface Servlet and the Servlet Life Cycle

Method Description void init( ServletConfig config )

The servlet container calls this method once during a servletrsquos execution cycle to initialize the

servlet The ServletConfig argument is supplied by the servlet container that executes the

servlet ServletConfig getServletConfig()

This method returns a reference to an object that implements interface ServletConfig This

object provides access to the servletrsquos configuration information such as servlet initialization

parameters and the servletrsquos ServletContext which provides the servlet with access to its

environment (ie the servlet container in which the servlet executes)

String getServletInfo()

This method is defined by a servlet programmer to return a string containing servlet information

such as the servletrsquos author and version void service( ServletRequest request ServletResponse response )

The servlet container calls this method to respond to a client request to the servlet

void destroy()

This ldquocleanuprdquo method is called when a servlet is terminated by its servlet container Resources

used by the servlet such as an open file or an open database connection should be deallocated here

Methods of interface Servlet (package javaxservlet)

HttpServlet Class

bull Web-based servlets typically extend HttpServlet

class

bull HttpServlet overrides method service

bull Two most common HTTP request types

ndash get requests (data rides on URL)

ndash post requests (data sent in a file)

bull Method doGet responds to get requests

public void doGet(HttpServletRequest request

HttpServletResponse response)

bull Method doPost responds to post requests

public void doPost(HttpServletRequest request

HttpServletResponse response)

HttpServlet Class

bull HttpServletRequest and

HttpServletResponse objects enable

interaction between client and server

HttpServletRequest Interface

bull Web server

ndash creates an HttpServletRequest object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

ndash HttpServletRequest object contains the request from

the client

HttpServletRequest Interface

Method Description String getParameter( String name )

Obtains the value of a parameter sent to the servlet as part of a get or post request The

name argument represents the parameter name Enumeration getParameterNames()

Returns the names of all the parameters sent to the servlet as part of a post request

String[] getParameterValues( String name )

For a parameter with multiple values this method returns an array of strings containing the

values for a specified servlet parameter Cookie[] getCookies()

Returns an array of Cookie objects stored on the client by the server Cookie objects can

be used to uniquely identify clients to the servlet HttpSession getSession( boolean create )

Returns an HttpSession object associated with the clientrsquos current browsing session

This method can create an HttpSession object (true argument) if one does not already

exist for the client HttpSession objects are used in similar ways to Cookies for

uniquely identifying clients

Fig 243 Some methods of interface HttpServletRequest

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

Servlet Life Cycle

ndash Servletrsquos service method handles requests (receives

processes sends response to client)

ndash Servletrsquos service method called once per request runs in

a Thread

ndash Servletrsquos destroy method releases servlet resources when

the servlet container terminates the servlet

Interface Servlet and the Servlet Life Cycle

Method Description void init( ServletConfig config )

The servlet container calls this method once during a servletrsquos execution cycle to initialize the

servlet The ServletConfig argument is supplied by the servlet container that executes the

servlet ServletConfig getServletConfig()

This method returns a reference to an object that implements interface ServletConfig This

object provides access to the servletrsquos configuration information such as servlet initialization

parameters and the servletrsquos ServletContext which provides the servlet with access to its

environment (ie the servlet container in which the servlet executes)

String getServletInfo()

This method is defined by a servlet programmer to return a string containing servlet information

such as the servletrsquos author and version void service( ServletRequest request ServletResponse response )

The servlet container calls this method to respond to a client request to the servlet

void destroy()

This ldquocleanuprdquo method is called when a servlet is terminated by its servlet container Resources

used by the servlet such as an open file or an open database connection should be deallocated here

Methods of interface Servlet (package javaxservlet)

HttpServlet Class

bull Web-based servlets typically extend HttpServlet

class

bull HttpServlet overrides method service

bull Two most common HTTP request types

ndash get requests (data rides on URL)

ndash post requests (data sent in a file)

bull Method doGet responds to get requests

public void doGet(HttpServletRequest request

HttpServletResponse response)

bull Method doPost responds to post requests

public void doPost(HttpServletRequest request

HttpServletResponse response)

HttpServlet Class

bull HttpServletRequest and

HttpServletResponse objects enable

interaction between client and server

HttpServletRequest Interface

bull Web server

ndash creates an HttpServletRequest object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

ndash HttpServletRequest object contains the request from

the client

HttpServletRequest Interface

Method Description String getParameter( String name )

Obtains the value of a parameter sent to the servlet as part of a get or post request The

name argument represents the parameter name Enumeration getParameterNames()

Returns the names of all the parameters sent to the servlet as part of a post request

String[] getParameterValues( String name )

For a parameter with multiple values this method returns an array of strings containing the

values for a specified servlet parameter Cookie[] getCookies()

Returns an array of Cookie objects stored on the client by the server Cookie objects can

be used to uniquely identify clients to the servlet HttpSession getSession( boolean create )

Returns an HttpSession object associated with the clientrsquos current browsing session

This method can create an HttpSession object (true argument) if one does not already

exist for the client HttpSession objects are used in similar ways to Cookies for

uniquely identifying clients

Fig 243 Some methods of interface HttpServletRequest

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

Interface Servlet and the Servlet Life Cycle

Method Description void init( ServletConfig config )

The servlet container calls this method once during a servletrsquos execution cycle to initialize the

servlet The ServletConfig argument is supplied by the servlet container that executes the

servlet ServletConfig getServletConfig()

This method returns a reference to an object that implements interface ServletConfig This

object provides access to the servletrsquos configuration information such as servlet initialization

parameters and the servletrsquos ServletContext which provides the servlet with access to its

environment (ie the servlet container in which the servlet executes)

String getServletInfo()

This method is defined by a servlet programmer to return a string containing servlet information

such as the servletrsquos author and version void service( ServletRequest request ServletResponse response )

The servlet container calls this method to respond to a client request to the servlet

void destroy()

This ldquocleanuprdquo method is called when a servlet is terminated by its servlet container Resources

used by the servlet such as an open file or an open database connection should be deallocated here

Methods of interface Servlet (package javaxservlet)

HttpServlet Class

bull Web-based servlets typically extend HttpServlet

class

bull HttpServlet overrides method service

bull Two most common HTTP request types

ndash get requests (data rides on URL)

ndash post requests (data sent in a file)

bull Method doGet responds to get requests

public void doGet(HttpServletRequest request

HttpServletResponse response)

bull Method doPost responds to post requests

public void doPost(HttpServletRequest request

HttpServletResponse response)

HttpServlet Class

bull HttpServletRequest and

HttpServletResponse objects enable

interaction between client and server

HttpServletRequest Interface

bull Web server

ndash creates an HttpServletRequest object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

ndash HttpServletRequest object contains the request from

the client

HttpServletRequest Interface

Method Description String getParameter( String name )

Obtains the value of a parameter sent to the servlet as part of a get or post request The

name argument represents the parameter name Enumeration getParameterNames()

Returns the names of all the parameters sent to the servlet as part of a post request

String[] getParameterValues( String name )

For a parameter with multiple values this method returns an array of strings containing the

values for a specified servlet parameter Cookie[] getCookies()

Returns an array of Cookie objects stored on the client by the server Cookie objects can

be used to uniquely identify clients to the servlet HttpSession getSession( boolean create )

Returns an HttpSession object associated with the clientrsquos current browsing session

This method can create an HttpSession object (true argument) if one does not already

exist for the client HttpSession objects are used in similar ways to Cookies for

uniquely identifying clients

Fig 243 Some methods of interface HttpServletRequest

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

HttpServlet Class

bull Web-based servlets typically extend HttpServlet

class

bull HttpServlet overrides method service

bull Two most common HTTP request types

ndash get requests (data rides on URL)

ndash post requests (data sent in a file)

bull Method doGet responds to get requests

public void doGet(HttpServletRequest request

HttpServletResponse response)

bull Method doPost responds to post requests

public void doPost(HttpServletRequest request

HttpServletResponse response)

HttpServlet Class

bull HttpServletRequest and

HttpServletResponse objects enable

interaction between client and server

HttpServletRequest Interface

bull Web server

ndash creates an HttpServletRequest object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

ndash HttpServletRequest object contains the request from

the client

HttpServletRequest Interface

Method Description String getParameter( String name )

Obtains the value of a parameter sent to the servlet as part of a get or post request The

name argument represents the parameter name Enumeration getParameterNames()

Returns the names of all the parameters sent to the servlet as part of a post request

String[] getParameterValues( String name )

For a parameter with multiple values this method returns an array of strings containing the

values for a specified servlet parameter Cookie[] getCookies()

Returns an array of Cookie objects stored on the client by the server Cookie objects can

be used to uniquely identify clients to the servlet HttpSession getSession( boolean create )

Returns an HttpSession object associated with the clientrsquos current browsing session

This method can create an HttpSession object (true argument) if one does not already

exist for the client HttpSession objects are used in similar ways to Cookies for

uniquely identifying clients

Fig 243 Some methods of interface HttpServletRequest

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

HttpServlet Class

bull HttpServletRequest and

HttpServletResponse objects enable

interaction between client and server

HttpServletRequest Interface

bull Web server

ndash creates an HttpServletRequest object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

ndash HttpServletRequest object contains the request from

the client

HttpServletRequest Interface

Method Description String getParameter( String name )

Obtains the value of a parameter sent to the servlet as part of a get or post request The

name argument represents the parameter name Enumeration getParameterNames()

Returns the names of all the parameters sent to the servlet as part of a post request

String[] getParameterValues( String name )

For a parameter with multiple values this method returns an array of strings containing the

values for a specified servlet parameter Cookie[] getCookies()

Returns an array of Cookie objects stored on the client by the server Cookie objects can

be used to uniquely identify clients to the servlet HttpSession getSession( boolean create )

Returns an HttpSession object associated with the clientrsquos current browsing session

This method can create an HttpSession object (true argument) if one does not already

exist for the client HttpSession objects are used in similar ways to Cookies for

uniquely identifying clients

Fig 243 Some methods of interface HttpServletRequest

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

HttpServletRequest Interface

bull Web server

ndash creates an HttpServletRequest object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

ndash HttpServletRequest object contains the request from

the client

HttpServletRequest Interface

Method Description String getParameter( String name )

Obtains the value of a parameter sent to the servlet as part of a get or post request The

name argument represents the parameter name Enumeration getParameterNames()

Returns the names of all the parameters sent to the servlet as part of a post request

String[] getParameterValues( String name )

For a parameter with multiple values this method returns an array of strings containing the

values for a specified servlet parameter Cookie[] getCookies()

Returns an array of Cookie objects stored on the client by the server Cookie objects can

be used to uniquely identify clients to the servlet HttpSession getSession( boolean create )

Returns an HttpSession object associated with the clientrsquos current browsing session

This method can create an HttpSession object (true argument) if one does not already

exist for the client HttpSession objects are used in similar ways to Cookies for

uniquely identifying clients

Fig 243 Some methods of interface HttpServletRequest

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

HttpServletRequest Interface

Method Description String getParameter( String name )

Obtains the value of a parameter sent to the servlet as part of a get or post request The

name argument represents the parameter name Enumeration getParameterNames()

Returns the names of all the parameters sent to the servlet as part of a post request

String[] getParameterValues( String name )

For a parameter with multiple values this method returns an array of strings containing the

values for a specified servlet parameter Cookie[] getCookies()

Returns an array of Cookie objects stored on the client by the server Cookie objects can

be used to uniquely identify clients to the servlet HttpSession getSession( boolean create )

Returns an HttpSession object associated with the clientrsquos current browsing session

This method can create an HttpSession object (true argument) if one does not already

exist for the client HttpSession objects are used in similar ways to Cookies for

uniquely identifying clients

Fig 243 Some methods of interface HttpServletRequest

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

HttpServletResponse Interface

bull Web server

ndash creates an HttpServletResponse object

ndash passes it to the servletrsquos service method (that is doGet

or doPost)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

HttpServletResponse Interface

Method Description void addCookie( Cookie cookie )

Used to add a Cookie to the header of the response to the client The

Cookiersquos maximum age and whether Cookies are enabled on the client

determine if Cookies are stored on the client ServletOutputStream getOutputStream()

Obtains a byte-based output stream for sending binary data to the client PrintWriter getWriter()

Obtains a character-based output stream for sending text data to the client void setContentType( String type )

Specifies the MIME type of the response to the browser The MIME type

helps the browser determine how to display the data (or possibly what

other application to execute to process the data) For example MIME type

texthtml indicates that the response is an HTML document so the

browser displays the HTML page

Fig 244 Some methods of interface HttpServletResponse

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

Handling HTTP get Requests

bull get request

ndash May send data on the URL this example does not

bull Example WelcomeServlet

ndash a servlet handles HTTP get requests

ndash responsesetContentType(texthtml)

provides the browser with Multipurpose Internet Mail

Extension (MIME) type

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

1 WelcomeServletjava

2 A simple servlet to process get requests

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet extends HttpServlet

9

10 process get requests from clients

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 responsesetContentType( texthtml )

16 PrintWriter out = responsegetWriter()

17

18 send HTML page to client

19

20 start HTML document

21

22

23

24

25

26

Import the javaxservlet and

javaxservlethttp packages

Extends HttpServlet to

handle HTTP get requests

and HTTP post requests

Override method doGet to

provide custom get request

processing

Uses the response objectrsquos

setContentType method to

specify the content type of the data to

be sent as the response to the client

Uses the response objectrsquos

getWriter method to obtain a

reference to the PrintWriter

object that enables the servlet to send

content to the client

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

27 outprintln( lthtmlgt )

28

29 head section of document

30 outprintln( ltheadgt )

31 outprintln( lttitlegtA Simple Servlet Examplelttitlegt )

32 outprintln( ltheadgt )

33

34 body section of document

35 outprintln( ltbodygt )

36 outprintln( lth1gtWelcome to Servletslth1gt )

37 outprintln( ltbodygt )

38

39 end HTML document

40 outprintln( lthtmlgt )

41 outclose() close stream to complete the page

42

43

Closes the output stream

flushes the output buffer

and sends the information

to the client

Create the HTML document by

writing strings with the out

objectrsquos println method

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- WelcomeServlethtml --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Get Requestlttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome1 method = getgt

14

15 ltpgtltlabelgtClick the button to invoke the servlet

16 ltinput type = submit value = Get HTML Document gt

17 ltlabelgtltpgt

18

19 ltformgt

20 ltbodygt

21 lthtmlgt

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

Program

output

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

Deploying a Web Application

bull Web applications

ndash JSPs servlets and their supporting files

bull Deploying a Web application

ndash Deployment descriptor

bull webxml

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

1 ltDOCTYPE web-app PUBLIC

2 -Sun Microsystems IncDTD Web Application 22EN

3 httpjavasuncomj2eedtdsweb-app_2_2dtdgt

4

5 ltweb-appgt

6

7 lt-- General description of your Web application --gt

8 ltdisplay-namegt

9 Java How to Program JSP

10 and Servlet Chapter Examples

11 ltdisplay-namegt

12

13 ltdescriptiongt

14 This is the Web application in which we

15 demonstrate our JSP and Servlet examples

16 ltdescriptiongt

17

18 lt-- Servlet definitions --gt

19 ltservletgt

20 ltservlet-namegtwelcome1ltservlet-namegt

21

22 ltdescriptiongt

23 A simple servlet that handles an HTTP get request

24 ltdescriptiongt

25

Element web-app defines the configuration

of each servlet in the Web application and

the servlet mapping for each servlet

Element display-name specifies

a name that can be displayed to the

administrator of the server on which

the Web application is installed

Element description specifies a

description of the Web application

that might be displayed to the

administrator of the server

Element servlet describes a servlet

Element servlet-name

is the name for the servlet

Element description

specifies a description for

this particular servlet

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

26 ltservlet-classgt

27 WelcomeServlet

28 ltservlet-classgt

29 ltservletgt

30

31 lt-- Servlet mappings --gt

32 ltservlet-mappinggt

33 ltservlet-namegtwelcome1ltservlet-namegt

34 lturl-patterngtwelcome1lturl-patterngt

35 ltservlet-mappinggt

36

37 ltweb-appgt

Element servlet-mapping

specifies servlet-name and

url-pattern elements

Element servlet-class

specifies compiled servletrsquos

fully qualified class name

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

Handling HTTP get Requests Containing

Data

bull Servlet WelcomeServlet2

ndash Responds to a get request that contains data

ndash Parameters passed as namevalue pairs on the URL

(httpwelcome2firstname=Paul)

ndash String firstName =

requestgetParameter(firstname)

bull retrieves the string ldquoPaulrdquo

bull retrieves null if no parameter has the name firstname

bull parameters typically come from HTML FORMs

bull servlet is called when SUBMIT button is clicked

ndash Multiple parameters separated by amprsquos

(httpwelcome2firstname=Paulamplastn

ame=Davisampidnum=22471)

1 WelcomeServlet2java

2 Processing HTTP get requests containing data

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet2 extends HttpServlet

9

10 process get request from client

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 String firstName = requestgetParameter( firstname )

16

17 responsesetContentType( texthtml )

18 PrintWriter out = responsegetWriter()

19

20 send HTML document to client

21

22 start HTML document

23 outprintln( ltxml version = 10gt )

24

The request objectrsquos

getParameter

method receives the

parameter name and

returns the

corresponding String

value

25 outprintln( ltDOCTYPE html PUBLIC -W3CDTD +

26 XHTML 10 StrictEN httpwwww3org +

27 TRxhtml1DTDxhtml1-strictdtdgt )

28

29 outprintln( lthtml xmlns = httpwwww3org1999xhtmlgt )

30

31 head section of document

32 outprintln( ltheadgt )

33 outprintln(

34 lttitlegtProcessing get requests with datalttitlegt )

35 outprintln( ltheadgt )

36

37 body section of document

38 outprintln( ltbodygt )

39 outprintln( lth1gtHello + firstName + ltbr gt )

40 outprintln( Welcome to Servletslth1gt )

41 outprintln( ltbodygt )

42

43 end XHTML document

44 outprintln( lthtmlgt )

45 outclose() close stream to complete the page

46

47

Uses the result of line

15 as part of the

response to the client

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- Fig 2412 WelcomeServlet2html --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtProcessing get requests with datalttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome2 method = getgt

14

15 ltpgtltlabelgt

16 Type your first name and press the Submit button

17 ltbr gtltinput type = text name = firstname gt

18 ltinput type = submit value = Submit gt

19 ltpgtltlabelgt

20

21 ltformgt

22 ltbodygt

23 lthtmlgt

Get the first name

from the user

Handling HTTP post Requests

bull HTTP post request

ndash Post data from an HTML form to a server-side form handler

using a file

ndash Browsers usually do NOT cache post requests

bull Search engines usually use ldquogetrdquo because just a

little data

ndash Browsers usually cache get requests

bull Servlet WelcomeServlet3

ndash Responds to a post request that contains data

1 WelcomeServlet3java

2 Processing post requests containing data

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet3 extends HttpServlet

9

10 process post request from client

11 protected void doPost( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 String firstName = requestgetParameter( firstname )

16

17 responsesetContentType( texthtml )

18 PrintWriter out = responsegetWriter()

19

20 send HTML page to client

21

22 start HTML document

23 outprintln( ltxml version = 10gt )

24

Declare a doPost method

to responds to post requests

25 outprintln( ltDOCTYPE html PUBLIC -W3CDTD +

26 XHTML 10 StrictEN httpwwww3org +

27 TRxhtml1DTDxhtml1-strictdtdgt )

28

29 outprintln( lthtml xmlns = httpwwww3org1999xhtmlgt )

30

31 head section of document

32 outprintln( ltheadgt )

33 outprintln(

34 lttitlegtProcessing post requests with datalttitlegt )

35 outprintln( ltheadgt )

36

37 body section of document

38 outprintln( ltbodygt )

39 outprintln( lth1gtHello + firstName + ltbr gt )

40 outprintln( Welcome to Servletslth1gt )

41 outprintln( ltbodygt )

42

43 end HTML document

44 outprintln( lthtmlgt )

45 outclose() close stream to complete the page

46

47

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- Fig 2415 WelcomeServlet3html --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Post Request with Datalttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome3 method = postgt

14

15 ltpgtltlabelgt

16 Type your first name and press the Submit button

17 ltbr gtltinput type = text name = firstname gt

18 ltinput type = submit value = Submit gt

19 ltlabelgtltpgt

20

21 ltformgt

22 ltbodygt

23 lthtmlgt

Provide a form in which the

user can input a name in the

text input element

firstname then click the

Submit button to invoke

WelcomeServlet3

Redirecting Requests to Other Resources

bull Servlet RedirectServlet

ndash Redirects the request to a different resource

ndash responsesendRedirect(URL)

bull redirects to that URL

bull immediately terminates current program

bull Use relative paths whenever possible to make Website portable

1 RedirectServletjava

2 Redirecting a user to a different Web page

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

8 public class RedirectServlet extends HttpServlet

10 process get request from client

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 String location = requestgetParameter( page )

16

17 if ( location = null )

18

19 if ( locationequals( deitel ) )

20 responsesendRedirect( httpwwwdeitelcom )

21 else

22 if ( locationequals( welcome1 ) )

23 responsesendRedirect( welcome1 )

24 outclose()

25

26

Obtains the page

parameter from the request

Determine if the value is either

ldquodeitelrdquo or ldquowelcome1rdquo Redirects the request to

wwwdeitelcom

Redirects the request to the

servlet WelcomeServlet

Multi-Tier Applications Using JDBC from a

Servlet

bull Servlets can communicate with databases via

JDBC

bull Three-tier distributed applications

ndash User interface

ndash Processing logic

ndash Database access

bull HTML user interface makes interface very

accessible across multiple platforms

bull Web servers often represent the middle tier

Multi-Tier Applications Using JDBC from a

Servlet

bull Three-tier distributed application example

ndash Studenthtml

ndash StudentServlet

ndash student database

Servlet-JDBC Example

Accept the roll number first name and division from

the student using html file and insert these values in

the student table using Servlet

Studenthtml

StudentServletjava

25 outprintln( ltDOCTYPE html PUBLIC -W3CDTD +

26 XHTML 10 StrictEN httpwwww3org +

27 TRxhtml1DTDxhtml1-strictdtdgt )

28

29 outprintln( lthtml xmlns = httpwwww3org1999xhtmlgt )

30

31 head section of document

32 outprintln( ltheadgt )

33 outprintln(

34 lttitlegtProcessing get requests with datalttitlegt )

35 outprintln( ltheadgt )

36

37 body section of document

38 outprintln( ltbodygt )

39 outprintln( lth1gtHello + firstName + ltbr gt )

40 outprintln( Welcome to Servletslth1gt )

41 outprintln( ltbodygt )

42

43 end XHTML document

44 outprintln( lthtmlgt )

45 outclose() close stream to complete the page

46

47

Uses the result of line

15 as part of the

response to the client

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- Fig 2412 WelcomeServlet2html --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtProcessing get requests with datalttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome2 method = getgt

14

15 ltpgtltlabelgt

16 Type your first name and press the Submit button

17 ltbr gtltinput type = text name = firstname gt

18 ltinput type = submit value = Submit gt

19 ltpgtltlabelgt

20

21 ltformgt

22 ltbodygt

23 lthtmlgt

Get the first name

from the user

Handling HTTP post Requests

bull HTTP post request

ndash Post data from an HTML form to a server-side form handler

using a file

ndash Browsers usually do NOT cache post requests

bull Search engines usually use ldquogetrdquo because just a

little data

ndash Browsers usually cache get requests

bull Servlet WelcomeServlet3

ndash Responds to a post request that contains data

1 WelcomeServlet3java

2 Processing post requests containing data

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet3 extends HttpServlet

9

10 process post request from client

11 protected void doPost( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 String firstName = requestgetParameter( firstname )

16

17 responsesetContentType( texthtml )

18 PrintWriter out = responsegetWriter()

19

20 send HTML page to client

21

22 start HTML document

23 outprintln( ltxml version = 10gt )

24

Declare a doPost method

to responds to post requests

25 outprintln( ltDOCTYPE html PUBLIC -W3CDTD +

26 XHTML 10 StrictEN httpwwww3org +

27 TRxhtml1DTDxhtml1-strictdtdgt )

28

29 outprintln( lthtml xmlns = httpwwww3org1999xhtmlgt )

30

31 head section of document

32 outprintln( ltheadgt )

33 outprintln(

34 lttitlegtProcessing post requests with datalttitlegt )

35 outprintln( ltheadgt )

36

37 body section of document

38 outprintln( ltbodygt )

39 outprintln( lth1gtHello + firstName + ltbr gt )

40 outprintln( Welcome to Servletslth1gt )

41 outprintln( ltbodygt )

42

43 end HTML document

44 outprintln( lthtmlgt )

45 outclose() close stream to complete the page

46

47

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- Fig 2415 WelcomeServlet3html --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Post Request with Datalttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome3 method = postgt

14

15 ltpgtltlabelgt

16 Type your first name and press the Submit button

17 ltbr gtltinput type = text name = firstname gt

18 ltinput type = submit value = Submit gt

19 ltlabelgtltpgt

20

21 ltformgt

22 ltbodygt

23 lthtmlgt

Provide a form in which the

user can input a name in the

text input element

firstname then click the

Submit button to invoke

WelcomeServlet3

Redirecting Requests to Other Resources

bull Servlet RedirectServlet

ndash Redirects the request to a different resource

ndash responsesendRedirect(URL)

bull redirects to that URL

bull immediately terminates current program

bull Use relative paths whenever possible to make Website portable

1 RedirectServletjava

2 Redirecting a user to a different Web page

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

8 public class RedirectServlet extends HttpServlet

10 process get request from client

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 String location = requestgetParameter( page )

16

17 if ( location = null )

18

19 if ( locationequals( deitel ) )

20 responsesendRedirect( httpwwwdeitelcom )

21 else

22 if ( locationequals( welcome1 ) )

23 responsesendRedirect( welcome1 )

24 outclose()

25

26

Obtains the page

parameter from the request

Determine if the value is either

ldquodeitelrdquo or ldquowelcome1rdquo Redirects the request to

wwwdeitelcom

Redirects the request to the

servlet WelcomeServlet

Multi-Tier Applications Using JDBC from a

Servlet

bull Servlets can communicate with databases via

JDBC

bull Three-tier distributed applications

ndash User interface

ndash Processing logic

ndash Database access

bull HTML user interface makes interface very

accessible across multiple platforms

bull Web servers often represent the middle tier

Multi-Tier Applications Using JDBC from a

Servlet

bull Three-tier distributed application example

ndash Studenthtml

ndash StudentServlet

ndash student database

Servlet-JDBC Example

Accept the roll number first name and division from

the student using html file and insert these values in

the student table using Servlet

Studenthtml

StudentServletjava

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- Fig 2412 WelcomeServlet2html --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtProcessing get requests with datalttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome2 method = getgt

14

15 ltpgtltlabelgt

16 Type your first name and press the Submit button

17 ltbr gtltinput type = text name = firstname gt

18 ltinput type = submit value = Submit gt

19 ltpgtltlabelgt

20

21 ltformgt

22 ltbodygt

23 lthtmlgt

Get the first name

from the user

Handling HTTP post Requests

bull HTTP post request

ndash Post data from an HTML form to a server-side form handler

using a file

ndash Browsers usually do NOT cache post requests

bull Search engines usually use ldquogetrdquo because just a

little data

ndash Browsers usually cache get requests

bull Servlet WelcomeServlet3

ndash Responds to a post request that contains data

1 WelcomeServlet3java

2 Processing post requests containing data

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet3 extends HttpServlet

9

10 process post request from client

11 protected void doPost( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 String firstName = requestgetParameter( firstname )

16

17 responsesetContentType( texthtml )

18 PrintWriter out = responsegetWriter()

19

20 send HTML page to client

21

22 start HTML document

23 outprintln( ltxml version = 10gt )

24

Declare a doPost method

to responds to post requests

25 outprintln( ltDOCTYPE html PUBLIC -W3CDTD +

26 XHTML 10 StrictEN httpwwww3org +

27 TRxhtml1DTDxhtml1-strictdtdgt )

28

29 outprintln( lthtml xmlns = httpwwww3org1999xhtmlgt )

30

31 head section of document

32 outprintln( ltheadgt )

33 outprintln(

34 lttitlegtProcessing post requests with datalttitlegt )

35 outprintln( ltheadgt )

36

37 body section of document

38 outprintln( ltbodygt )

39 outprintln( lth1gtHello + firstName + ltbr gt )

40 outprintln( Welcome to Servletslth1gt )

41 outprintln( ltbodygt )

42

43 end HTML document

44 outprintln( lthtmlgt )

45 outclose() close stream to complete the page

46

47

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- Fig 2415 WelcomeServlet3html --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Post Request with Datalttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome3 method = postgt

14

15 ltpgtltlabelgt

16 Type your first name and press the Submit button

17 ltbr gtltinput type = text name = firstname gt

18 ltinput type = submit value = Submit gt

19 ltlabelgtltpgt

20

21 ltformgt

22 ltbodygt

23 lthtmlgt

Provide a form in which the

user can input a name in the

text input element

firstname then click the

Submit button to invoke

WelcomeServlet3

Redirecting Requests to Other Resources

bull Servlet RedirectServlet

ndash Redirects the request to a different resource

ndash responsesendRedirect(URL)

bull redirects to that URL

bull immediately terminates current program

bull Use relative paths whenever possible to make Website portable

1 RedirectServletjava

2 Redirecting a user to a different Web page

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

8 public class RedirectServlet extends HttpServlet

10 process get request from client

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 String location = requestgetParameter( page )

16

17 if ( location = null )

18

19 if ( locationequals( deitel ) )

20 responsesendRedirect( httpwwwdeitelcom )

21 else

22 if ( locationequals( welcome1 ) )

23 responsesendRedirect( welcome1 )

24 outclose()

25

26

Obtains the page

parameter from the request

Determine if the value is either

ldquodeitelrdquo or ldquowelcome1rdquo Redirects the request to

wwwdeitelcom

Redirects the request to the

servlet WelcomeServlet

Multi-Tier Applications Using JDBC from a

Servlet

bull Servlets can communicate with databases via

JDBC

bull Three-tier distributed applications

ndash User interface

ndash Processing logic

ndash Database access

bull HTML user interface makes interface very

accessible across multiple platforms

bull Web servers often represent the middle tier

Multi-Tier Applications Using JDBC from a

Servlet

bull Three-tier distributed application example

ndash Studenthtml

ndash StudentServlet

ndash student database

Servlet-JDBC Example

Accept the roll number first name and division from

the student using html file and insert these values in

the student table using Servlet

Studenthtml

StudentServletjava

Handling HTTP post Requests

bull HTTP post request

ndash Post data from an HTML form to a server-side form handler

using a file

ndash Browsers usually do NOT cache post requests

bull Search engines usually use ldquogetrdquo because just a

little data

ndash Browsers usually cache get requests

bull Servlet WelcomeServlet3

ndash Responds to a post request that contains data

1 WelcomeServlet3java

2 Processing post requests containing data

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet3 extends HttpServlet

9

10 process post request from client

11 protected void doPost( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 String firstName = requestgetParameter( firstname )

16

17 responsesetContentType( texthtml )

18 PrintWriter out = responsegetWriter()

19

20 send HTML page to client

21

22 start HTML document

23 outprintln( ltxml version = 10gt )

24

Declare a doPost method

to responds to post requests

25 outprintln( ltDOCTYPE html PUBLIC -W3CDTD +

26 XHTML 10 StrictEN httpwwww3org +

27 TRxhtml1DTDxhtml1-strictdtdgt )

28

29 outprintln( lthtml xmlns = httpwwww3org1999xhtmlgt )

30

31 head section of document

32 outprintln( ltheadgt )

33 outprintln(

34 lttitlegtProcessing post requests with datalttitlegt )

35 outprintln( ltheadgt )

36

37 body section of document

38 outprintln( ltbodygt )

39 outprintln( lth1gtHello + firstName + ltbr gt )

40 outprintln( Welcome to Servletslth1gt )

41 outprintln( ltbodygt )

42

43 end HTML document

44 outprintln( lthtmlgt )

45 outclose() close stream to complete the page

46

47

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- Fig 2415 WelcomeServlet3html --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Post Request with Datalttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome3 method = postgt

14

15 ltpgtltlabelgt

16 Type your first name and press the Submit button

17 ltbr gtltinput type = text name = firstname gt

18 ltinput type = submit value = Submit gt

19 ltlabelgtltpgt

20

21 ltformgt

22 ltbodygt

23 lthtmlgt

Provide a form in which the

user can input a name in the

text input element

firstname then click the

Submit button to invoke

WelcomeServlet3

Redirecting Requests to Other Resources

bull Servlet RedirectServlet

ndash Redirects the request to a different resource

ndash responsesendRedirect(URL)

bull redirects to that URL

bull immediately terminates current program

bull Use relative paths whenever possible to make Website portable

1 RedirectServletjava

2 Redirecting a user to a different Web page

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

8 public class RedirectServlet extends HttpServlet

10 process get request from client

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 String location = requestgetParameter( page )

16

17 if ( location = null )

18

19 if ( locationequals( deitel ) )

20 responsesendRedirect( httpwwwdeitelcom )

21 else

22 if ( locationequals( welcome1 ) )

23 responsesendRedirect( welcome1 )

24 outclose()

25

26

Obtains the page

parameter from the request

Determine if the value is either

ldquodeitelrdquo or ldquowelcome1rdquo Redirects the request to

wwwdeitelcom

Redirects the request to the

servlet WelcomeServlet

Multi-Tier Applications Using JDBC from a

Servlet

bull Servlets can communicate with databases via

JDBC

bull Three-tier distributed applications

ndash User interface

ndash Processing logic

ndash Database access

bull HTML user interface makes interface very

accessible across multiple platforms

bull Web servers often represent the middle tier

Multi-Tier Applications Using JDBC from a

Servlet

bull Three-tier distributed application example

ndash Studenthtml

ndash StudentServlet

ndash student database

Servlet-JDBC Example

Accept the roll number first name and division from

the student using html file and insert these values in

the student table using Servlet

Studenthtml

StudentServletjava

1 WelcomeServlet3java

2 Processing post requests containing data

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

7

8 public class WelcomeServlet3 extends HttpServlet

9

10 process post request from client

11 protected void doPost( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 String firstName = requestgetParameter( firstname )

16

17 responsesetContentType( texthtml )

18 PrintWriter out = responsegetWriter()

19

20 send HTML page to client

21

22 start HTML document

23 outprintln( ltxml version = 10gt )

24

Declare a doPost method

to responds to post requests

25 outprintln( ltDOCTYPE html PUBLIC -W3CDTD +

26 XHTML 10 StrictEN httpwwww3org +

27 TRxhtml1DTDxhtml1-strictdtdgt )

28

29 outprintln( lthtml xmlns = httpwwww3org1999xhtmlgt )

30

31 head section of document

32 outprintln( ltheadgt )

33 outprintln(

34 lttitlegtProcessing post requests with datalttitlegt )

35 outprintln( ltheadgt )

36

37 body section of document

38 outprintln( ltbodygt )

39 outprintln( lth1gtHello + firstName + ltbr gt )

40 outprintln( Welcome to Servletslth1gt )

41 outprintln( ltbodygt )

42

43 end HTML document

44 outprintln( lthtmlgt )

45 outclose() close stream to complete the page

46

47

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- Fig 2415 WelcomeServlet3html --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Post Request with Datalttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome3 method = postgt

14

15 ltpgtltlabelgt

16 Type your first name and press the Submit button

17 ltbr gtltinput type = text name = firstname gt

18 ltinput type = submit value = Submit gt

19 ltlabelgtltpgt

20

21 ltformgt

22 ltbodygt

23 lthtmlgt

Provide a form in which the

user can input a name in the

text input element

firstname then click the

Submit button to invoke

WelcomeServlet3

Redirecting Requests to Other Resources

bull Servlet RedirectServlet

ndash Redirects the request to a different resource

ndash responsesendRedirect(URL)

bull redirects to that URL

bull immediately terminates current program

bull Use relative paths whenever possible to make Website portable

1 RedirectServletjava

2 Redirecting a user to a different Web page

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

8 public class RedirectServlet extends HttpServlet

10 process get request from client

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 String location = requestgetParameter( page )

16

17 if ( location = null )

18

19 if ( locationequals( deitel ) )

20 responsesendRedirect( httpwwwdeitelcom )

21 else

22 if ( locationequals( welcome1 ) )

23 responsesendRedirect( welcome1 )

24 outclose()

25

26

Obtains the page

parameter from the request

Determine if the value is either

ldquodeitelrdquo or ldquowelcome1rdquo Redirects the request to

wwwdeitelcom

Redirects the request to the

servlet WelcomeServlet

Multi-Tier Applications Using JDBC from a

Servlet

bull Servlets can communicate with databases via

JDBC

bull Three-tier distributed applications

ndash User interface

ndash Processing logic

ndash Database access

bull HTML user interface makes interface very

accessible across multiple platforms

bull Web servers often represent the middle tier

Multi-Tier Applications Using JDBC from a

Servlet

bull Three-tier distributed application example

ndash Studenthtml

ndash StudentServlet

ndash student database

Servlet-JDBC Example

Accept the roll number first name and division from

the student using html file and insert these values in

the student table using Servlet

Studenthtml

StudentServletjava

25 outprintln( ltDOCTYPE html PUBLIC -W3CDTD +

26 XHTML 10 StrictEN httpwwww3org +

27 TRxhtml1DTDxhtml1-strictdtdgt )

28

29 outprintln( lthtml xmlns = httpwwww3org1999xhtmlgt )

30

31 head section of document

32 outprintln( ltheadgt )

33 outprintln(

34 lttitlegtProcessing post requests with datalttitlegt )

35 outprintln( ltheadgt )

36

37 body section of document

38 outprintln( ltbodygt )

39 outprintln( lth1gtHello + firstName + ltbr gt )

40 outprintln( Welcome to Servletslth1gt )

41 outprintln( ltbodygt )

42

43 end HTML document

44 outprintln( lthtmlgt )

45 outclose() close stream to complete the page

46

47

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- Fig 2415 WelcomeServlet3html --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Post Request with Datalttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome3 method = postgt

14

15 ltpgtltlabelgt

16 Type your first name and press the Submit button

17 ltbr gtltinput type = text name = firstname gt

18 ltinput type = submit value = Submit gt

19 ltlabelgtltpgt

20

21 ltformgt

22 ltbodygt

23 lthtmlgt

Provide a form in which the

user can input a name in the

text input element

firstname then click the

Submit button to invoke

WelcomeServlet3

Redirecting Requests to Other Resources

bull Servlet RedirectServlet

ndash Redirects the request to a different resource

ndash responsesendRedirect(URL)

bull redirects to that URL

bull immediately terminates current program

bull Use relative paths whenever possible to make Website portable

1 RedirectServletjava

2 Redirecting a user to a different Web page

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

8 public class RedirectServlet extends HttpServlet

10 process get request from client

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 String location = requestgetParameter( page )

16

17 if ( location = null )

18

19 if ( locationequals( deitel ) )

20 responsesendRedirect( httpwwwdeitelcom )

21 else

22 if ( locationequals( welcome1 ) )

23 responsesendRedirect( welcome1 )

24 outclose()

25

26

Obtains the page

parameter from the request

Determine if the value is either

ldquodeitelrdquo or ldquowelcome1rdquo Redirects the request to

wwwdeitelcom

Redirects the request to the

servlet WelcomeServlet

Multi-Tier Applications Using JDBC from a

Servlet

bull Servlets can communicate with databases via

JDBC

bull Three-tier distributed applications

ndash User interface

ndash Processing logic

ndash Database access

bull HTML user interface makes interface very

accessible across multiple platforms

bull Web servers often represent the middle tier

Multi-Tier Applications Using JDBC from a

Servlet

bull Three-tier distributed application example

ndash Studenthtml

ndash StudentServlet

ndash student database

Servlet-JDBC Example

Accept the roll number first name and division from

the student using html file and insert these values in

the student table using Servlet

Studenthtml

StudentServletjava

1 ltxml version = 10gt

2 ltDOCTYPE html PUBLIC -W3CDTD XHTML 10 StrictEN

3 httpwwww3orgTRxhtml1DTDxhtml1-strictdtdgt

4

5 lt-- Fig 2415 WelcomeServlet3html --gt

6

7 lthtml xmlns = httpwwww3org1999xhtmlgt

8 ltheadgt

9 lttitlegtHandling an HTTP Post Request with Datalttitlegt

10 ltheadgt

11

12 ltbodygt

13 ltform action = jhtp5welcome3 method = postgt

14

15 ltpgtltlabelgt

16 Type your first name and press the Submit button

17 ltbr gtltinput type = text name = firstname gt

18 ltinput type = submit value = Submit gt

19 ltlabelgtltpgt

20

21 ltformgt

22 ltbodygt

23 lthtmlgt

Provide a form in which the

user can input a name in the

text input element

firstname then click the

Submit button to invoke

WelcomeServlet3

Redirecting Requests to Other Resources

bull Servlet RedirectServlet

ndash Redirects the request to a different resource

ndash responsesendRedirect(URL)

bull redirects to that URL

bull immediately terminates current program

bull Use relative paths whenever possible to make Website portable

1 RedirectServletjava

2 Redirecting a user to a different Web page

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

8 public class RedirectServlet extends HttpServlet

10 process get request from client

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 String location = requestgetParameter( page )

16

17 if ( location = null )

18

19 if ( locationequals( deitel ) )

20 responsesendRedirect( httpwwwdeitelcom )

21 else

22 if ( locationequals( welcome1 ) )

23 responsesendRedirect( welcome1 )

24 outclose()

25

26

Obtains the page

parameter from the request

Determine if the value is either

ldquodeitelrdquo or ldquowelcome1rdquo Redirects the request to

wwwdeitelcom

Redirects the request to the

servlet WelcomeServlet

Multi-Tier Applications Using JDBC from a

Servlet

bull Servlets can communicate with databases via

JDBC

bull Three-tier distributed applications

ndash User interface

ndash Processing logic

ndash Database access

bull HTML user interface makes interface very

accessible across multiple platforms

bull Web servers often represent the middle tier

Multi-Tier Applications Using JDBC from a

Servlet

bull Three-tier distributed application example

ndash Studenthtml

ndash StudentServlet

ndash student database

Servlet-JDBC Example

Accept the roll number first name and division from

the student using html file and insert these values in

the student table using Servlet

Studenthtml

StudentServletjava

Redirecting Requests to Other Resources

bull Servlet RedirectServlet

ndash Redirects the request to a different resource

ndash responsesendRedirect(URL)

bull redirects to that URL

bull immediately terminates current program

bull Use relative paths whenever possible to make Website portable

1 RedirectServletjava

2 Redirecting a user to a different Web page

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

8 public class RedirectServlet extends HttpServlet

10 process get request from client

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 String location = requestgetParameter( page )

16

17 if ( location = null )

18

19 if ( locationequals( deitel ) )

20 responsesendRedirect( httpwwwdeitelcom )

21 else

22 if ( locationequals( welcome1 ) )

23 responsesendRedirect( welcome1 )

24 outclose()

25

26

Obtains the page

parameter from the request

Determine if the value is either

ldquodeitelrdquo or ldquowelcome1rdquo Redirects the request to

wwwdeitelcom

Redirects the request to the

servlet WelcomeServlet

Multi-Tier Applications Using JDBC from a

Servlet

bull Servlets can communicate with databases via

JDBC

bull Three-tier distributed applications

ndash User interface

ndash Processing logic

ndash Database access

bull HTML user interface makes interface very

accessible across multiple platforms

bull Web servers often represent the middle tier

Multi-Tier Applications Using JDBC from a

Servlet

bull Three-tier distributed application example

ndash Studenthtml

ndash StudentServlet

ndash student database

Servlet-JDBC Example

Accept the roll number first name and division from

the student using html file and insert these values in

the student table using Servlet

Studenthtml

StudentServletjava

1 RedirectServletjava

2 Redirecting a user to a different Web page

3

4 import javaxservlet

5 import javaxservlethttp

6 import javaio

8 public class RedirectServlet extends HttpServlet

10 process get request from client

11 protected void doGet( HttpServletRequest request

12 HttpServletResponse response )

13 throws ServletException IOException

14

15 String location = requestgetParameter( page )

16

17 if ( location = null )

18

19 if ( locationequals( deitel ) )

20 responsesendRedirect( httpwwwdeitelcom )

21 else

22 if ( locationequals( welcome1 ) )

23 responsesendRedirect( welcome1 )

24 outclose()

25

26

Obtains the page

parameter from the request

Determine if the value is either

ldquodeitelrdquo or ldquowelcome1rdquo Redirects the request to

wwwdeitelcom

Redirects the request to the

servlet WelcomeServlet

Multi-Tier Applications Using JDBC from a

Servlet

bull Servlets can communicate with databases via

JDBC

bull Three-tier distributed applications

ndash User interface

ndash Processing logic

ndash Database access

bull HTML user interface makes interface very

accessible across multiple platforms

bull Web servers often represent the middle tier

Multi-Tier Applications Using JDBC from a

Servlet

bull Three-tier distributed application example

ndash Studenthtml

ndash StudentServlet

ndash student database

Servlet-JDBC Example

Accept the roll number first name and division from

the student using html file and insert these values in

the student table using Servlet

Studenthtml

StudentServletjava

Multi-Tier Applications Using JDBC from a

Servlet

bull Servlets can communicate with databases via

JDBC

bull Three-tier distributed applications

ndash User interface

ndash Processing logic

ndash Database access

bull HTML user interface makes interface very

accessible across multiple platforms

bull Web servers often represent the middle tier

Multi-Tier Applications Using JDBC from a

Servlet

bull Three-tier distributed application example

ndash Studenthtml

ndash StudentServlet

ndash student database

Servlet-JDBC Example

Accept the roll number first name and division from

the student using html file and insert these values in

the student table using Servlet

Studenthtml

StudentServletjava

Multi-Tier Applications Using JDBC from a

Servlet

bull Three-tier distributed application example

ndash Studenthtml

ndash StudentServlet

ndash student database

Servlet-JDBC Example

Accept the roll number first name and division from

the student using html file and insert these values in

the student table using Servlet

Studenthtml

StudentServletjava

Servlet-JDBC Example

Accept the roll number first name and division from

the student using html file and insert these values in

the student table using Servlet

Studenthtml

StudentServletjava