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Page 1Presentation Name HTC Confidential

J2EE Training

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3.Advanced-Java Contents -1

3.1.JDBC

3.2.Servlets & JSP

3.3.Tag Libraries

3.4.Struts 3.5.Struts-Tag Libraries 3.6.JSTL

3.7.XML

3.8.Junit 3.9.Ant

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3.1.JDBC

JDBC indicates Java Database Connectivity

The java.sql package makes it possible to connect to arelational database, send SQL commands to the database,process the returned results and invoke stored procedures

JDBC is database independent, so that the same codeworks with all databases vix. Sybase, Oracle, DB2,Informix...

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3.1.JDBC

JDBC Drivers To Connect to any database, we need to load (register)

programs called Drivers to interact with that particulardatabase :

Class.forName( JDBCDriver );

The following are types of JDBC drivers : Type 1 :- JDBC-ODBC Bridge

Provides JDBC access via ODBC Drivers

Type 2 :- Native API Driver

This kind of driver converts JDBC calls into callson the client API for Oracle, Sybase, Informix,DB2, or other DBMS

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3.1.JDBC

JDBC Drivers The following are types of JDBC drivers :

Type 3 :- JDBC-Net Driver

This driver translates JDBC calls into a DBMS-independent net protocol which is thentranslated to a DBMS protocol by a server. Thisnet server middleware is able to connect itspure Java clients to many different databases

Type 4 :- Native protocol Driver

This kind of driver converts JDBC calls into thenetwork protocol used by DBMSs directly. Thisallows a direct call from the client machine tothe DBMS server

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3.1.JDBC

Connection A Connection object represents a connection with a

database.

A connection session includes the SQL statements that

are executed and the results that are returned overthat connection.

A single application can have one or more connectionswith a single database, or it can have connections withmany different databases.

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3.1.JDBC

Connection The standard way to establish a connection with a

database is to call :DriverManager.getConnection( JDBCURL

[, ,]);

This method takes a string containing a JDBC URL andan optional User ID/ Password (for those databaseswhich require them).

A JDBC URL provides a way of identifying a databaseso that the appropriate driver will recognize it andestablish a connection

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3.1.JDBC

Connection Since JDBC URLs are used with various kinds of

drivers, the conventions are of necessity very flexible

The JDBC URL may refer to a logical host or database

name that is translated to the actual name by anetwork naming system

The standard syntax for JDBC URLs is shown below. Ithas three parts, which are separated by colons:

jdbc::

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3.1.JDBC

Connection The JDBC URL is broken down as follows:

jdbc

The protocol. The protocol in a JDBC URL is jdbc.

The name of the driver or the name of a databaseconnectivity mechanism

A way to identify the database. The subname can vary,depending on the subprotocol, and it can have any syntaxthe driver writer chooses.

jdbc:odbc:wombat (where wombat is the DSN)

jdbc:oracle:thin:@taz:1521:ops001

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3.1.JDBC

Connection The DriverManager class is referred to as the JDBC

management layer

The DriverManager class maintains a list of registeredDriver classes, and when the method getConnection is

called, it checks with each driver in the list until it findsone that can connect to the database specified in theURL.

The Driver method connect( ) uses this URL to actually

establish the connection.

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3.1.JDBC

Statements Once a connection is established, it is used to pass

SQL statements to its underlying database.

JDBC does not put any restrictions on the kinds of SQL

statements that can be sent; this provides a great dealof flexibility

JDBC provides three classes for sending SQLstatements to the database viz. Statement,PreparedStatement and CallableStatement.

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3.1.JDBC

Statements :-- Statement

A Statement object is used for sending simpleSQL statements.

PreparedStatement A PreparedStatement object is used for SQL

statements that take one or more parameters asinput arguments (IN parameters).

CallableStatement A CallableStatement object is used to execute

SQL stored procedures

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3.1.JDBC

Statement Created by the method createStatement( ) of the

Connection interface.Statement stm = con.createStatement( );

Key Methods

executeQuery( )

Is used for statements that produce a singleresult set, such as SELECT statements

executeUpdate( )

Is used to execute INSERT, UPDATE, or DELETEstatements and also SQL DDL (Data DefinitionLanguage) statements like CREATE TABLE andDROP TABLE

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3.1.JDBC

Statement Key Methods

execute( )

Is used to execute statements that return more than oneresult set, more than one update count, or a combination

of the two close( )

Releases this Statement object's database and JDBCresources immediately instead of waiting for this tohappen when it is automatically closed

setMaxRows( )

Sets the limit for the maximum number of rows that anyresult set can contain

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3.1.JDBC

Transactions A transaction consists of SQL statement(s) that have

been executed, completed, and then either committedor rolled back.

The method commit( ) of the Connection interfacemakes permanent any changes an SQL statementmakes to a database. The method rollback( ) willdiscard those changes.

When the method commit( ) or rollback( ) is called, thecurrent transaction ends.

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3.1.JDBC

Transactions A new connection is in auto-commit mode by default,

meaning that when a statement is completed, themethod commit( ) will be called on that statement

automatically. In this case, since each statement is committedindividually, a transaction consists of only onestatement.

If auto-commit mode has been disabled, a transactionwill not terminate until explicitly the commit( ) orrollback( ) is called.

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3.1.JDBC

ResultSet A ResultSet contains all of the rows which satisfied the

conditions in an SQL statement, and it provides accessto the data in those rows through a set of get methods

that allow access to the various columns of the currentrow.

The ResultSet.next( ) method is used to move to thenext row of the ResultSet, making the next rowbecome the current row.

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3.1.JDBC

ResultSet The general form of a result set is a table with column

headings and the corresponding values returned by aquery

The getXXX( ) methods provide the means forretrieving column values from the current row in aResultSet

Either the column name or the column number can beused to designate the column from which to retrievedata.

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3.1.JDBC

ResultSet For example, if the second column of a ResultSet

object is named title, to retrieve the value stored inthat column, use:

String s = rs.getString("title"); (or)String s = rs.getString(2);

Methods such as getString, getBigDecimal, getBytes,getDate, getTime, getTimestamp, getObject, getByte,getShort, getInt, getLong, getFloat, getDouble and

getBoolean are available in the ResultSet to receive thedata in the appropriate type.

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3.1.JDBC

ResultSet Information about the columns in a ResultSet is

available by calling the method getMetaData( ).

The ResultSetMetaData object returned gives the

number, types, and properties of its ResultSet object'scolumns.

To get the column names and type :ResultSetMetaData rsm = rs.getMetaData( );

for (int I =1; I < rsm.getColumnCount( ); I++)

System.out.println(Column : + rsm.getColumnName(I) +is of Type : + rsm.getColumnTypeName(I));

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3.1.JDBC

Sample code to Select data :import java.sql.*;

public class TestJDBC {

public static void main(String args[ ]) {

try {

// Load the JDBC Driver

Class.forName(oracle.jdbc.driver.OracleDriver);

} catch(ClassNotFoundException e) {

System.out.println(Error loading Driver : +e.toString( ));

}

Connection con = null;

Statement stm = null;Resultset rs = null; // Contd...

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3.1.JDBC

try {// Get a connection to the Database

con = DriverManager.getConnection(jdbc:oracle:thin:@taz:1521:ops001, trng , trng);

// Create a statement

stm=con.createStatement( );

// Execute an SQL Select statement

rs = stm.executeQuery(select ENO, ENAME from EMP);

if (rs == null)

System.out.println(No Data Found);

// Iterate through the Resultset to get Data

while (rs.next( )) {

System.out.println(Employee : + rs.getString(ENO) + - + rs.getString(ENAME));

} // Contd...

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3.1.JDBC

} catch(SQLException e) {System.out.println( JDBC Error : + e.getMessage( ));

} finally { // Close Resultset, Statement and Connection

try {

if (rs != null) rs.close( );

} catch(SQLException e) { }

try {

if (stm != null) stm.close( );


try {

if (con != null) con.close( );


}

}

}

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3.1.JDBC

Sample code to Insert data :import java.sql.*;

public class TestJDBC {

public static void main(String args[ ]) {

try {

// Load the JDBC Driver

Class.forName(oracle.jdbc.driver.OracleDriver);

} catch(ClassNotFoundException e) {

System.out.println(Error loading Driver : +e.toString( ));

}

Connection con = null;

Statement stm = null; // Contd...

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3.1.JDBC

try {// Get a connection to the Database

con = DriverManager.getConnection(jdbc:oracle:thin:@taz:1521:ops001, trng , trng);

// Create a statement

stm=con.createStatement( );

// Execute an SQL DML Statement

int returnStat = stm.executeUpdate(insert into EMP(ENO, ENAME ) values ( 1234, SHIVA ));

System.out.println(Inserted with return status : + returnStat);

// Contd...

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3.1.JDBC

} catch(SQLException e) {System.out.println( JDBC Error : + e.getMessage( ));

} finally { // Close Resultset, Statement and Connection

try {

if (rs != null) rs.close( );


try {

if (stm != null) stm.close( );


try {

if (con != null) con.close( );


}

}

}

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3.1.JDBC

PreparedStatement

A PreparedStatement is more efficient than aStatement object because it has been pre-compiledand stored for future use.

A PreparedStatement object is used for SQL

statements that take one or more parameters as inputarguments (IN parameters) and those SQL statementsthat need to be executed repeatedly.

Instances of PreparedStatement extend Statement and

include Statement methods.

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3.1.JDBC

PreparedS

tatement Created by the prepareStatement( ) method of theConnection interface.

PreparedStatement pstmt =con.prepareStatement (insert into EMP(ENO , ENAME) values ( ? , ? ));

An IN parameter is the one whose value is notspecified when the SQL statement is created, insteadthe question mark ("?") acts as a placeholder for IN

parameters. A value for each question mark must be supplied by

the appropriate setXXX method before the statement isexecuted.

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3.1.JDBC

PreparedStatement Once a parameter value has been set for a given statement, it can

be used for multiple executions of that statement.

For example, the following inserts 4 rows

PreparedStatement pstmt = con.prepareStatement( insertinto EMP (ENO , ENAME) values ( ? , ? ));

pstmt.setString(2, Shiva); //Constant parameter

for (int i= 1; i < 5; i++) {

pstmt.setInt(1, i); //Dynamic parameter

int status = pstmt.executeUpdate( );

}

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3.1.JDBC

CallableStatement CallableStatement objects are used to execute SQL

stored procedures

A CallableStatement object inherits methods for

handling IN parameters from PreparedStatement itadds methods for handling OUT and INOUTparameters.

The syntax for invoking a stored procedure in JDBC isshown below :

{call procedure_name(?, ?, ...)}

CallableStatement cstmt = con.prepareCall({call getTestData(?, ?)} );

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3.1.JDBC

CallableStatement Passing in any IN parameter values to a

CallableStatement object is done using the setXXXmethods as in PreparedStatement.

The JDBC type of each OUT parameter must beregistered before the CallableStatement object can beexecuted using the method registerOutParameter.

After the statement has been executed,CallableStatement's getXXX methods are used toretrieve the parameter value

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3.1.JDBC

CallableS

tatement The following code executes a Stored Procedure,passes an IN parameter and retrieves two OUTparameters :

CallableStatement cstmt = con.prepareCall(

{call getTestData(?, ? , ?)});cstmt.setInt(1, 25);

cstmt.registerOutParameter(2, java.sql.Types.VARCHAR);

cstmt.registerOutParameter(3, java.sql.Types.DECIMAL,3);

cstmt.executeUpdate( );

String s = cstmt.getString(2);

java.math.BigDecimal n = cstmt.getBigDecimal(3, 3);

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3.1.JDBC

In JDBC 2.0 we can get ResultSets that allowusers to scroll in both directions.

This is achieved through using II nd or IV th typeof drivers like

oracle.jdbc.driver.OracleDriver class object withurl jdbc:oracle:oci (oracle9 II nd type) orjdbc:oracle:thin:@hostname:1521:sid (oracle9 IVth) then using special createStatement() method

This ResultSet has methods likeprevious(),last(),first(),beforFirst(),afterLast(),absolute(int),relative(int) for navigation

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3.1.JDBC

3.2.Servlets & JSP

3.3.Tag Libraries

3.4.Struts 3.5.Struts-Tag Libraries 3.6.JSTL

3.7.XML

3.8.Junit 3.9.Ant

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3.2.Servlets

-3.2.1.Introduction to Servlets

3.2.2.Life Cycle of Servlets

3.2.3.A Sample HTTP Servlet

3.2.4.HTTP Servlet-Anatomy

3.2.5.HTTP Servlet- Session Management

3.2.6.ServletContext and ServletConfig

3.2.7.HTTP Servlet- Cookies

3.2.8.Servlet-info in web configuration file

3.2.9.servlet resource-access

3.2.9.1.filter,filter-mappings

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3.2.1.Introduction to Servlets

Servlets are server-side Java programs

extend the functionality of WEB Servers

are to WEB Servers what Applets are to WEB Browsers

are Request/Response oriented are Platform / WEB Server independent

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Servlets are initialized and loaded only once

are Multi-Threaded to handle multiple concurrent clientrequests

are not tied any particular protocol, but, are most

commonly used with HTTP manage state information on top of the stateless HTTP

are run by a Servlet Engine in a restrictiveSandbox(servlet container) for hacker prevention

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Servlets are used in the following cases processing the data captured in a HTML Form and

updating a database

retrieving data from a database and dynamically

generating HTML pages applications that requires state management like

shopping carts...

on-line conferencing and Chat applications

communicating with other Servers accessing existing Business systems

In MVC2 architecture,they are visualized as controllercomponents

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Why Servlets ? servlets are light-weight i.e. can run in the same

server process as the WEB server

servlets support a higher user load with less machine

resources servlets can be loaded from anywhere i.e.Local File

system / Remote Web site

servlets deliver faster on-line response as dont fork anew process for each request

Servlets can easily acess java api like JDBC, EJB, JMS,JavaMail, JavaIDL, RMI, or third-party Java technology

These are easily compatiable with most of web-servers

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WEB Servers supporting Servlets: Apache

Netscape Enterprise Server

IBM WebSphere

Lotus Domino GO Tandem iTP

Weblogic

Paralogic WebCore

And MORE

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Engines for Existing Servers: ServletExec

for IIS, Netscape, all Mac OS Servers

Jrun

for IIS, Netscape, Apache, WebSite Pro, WebSTAR WAICoolRunner

for Netscape

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All Servlets implement the interfacejavax.servlet.Servlet

Most Servlets extend one of the following 2standard implementations:

javax.servlet.GenericServlet

javax.servlet.http.HttpServlet

WEB applications use HTTP Servlets

HTTP Servlets extend Generic Servlet

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3.2.Servlets




3.2.4.HTTP Servlet-Anatomy 3.2.5.HTTP Servlet- Session Management



3.2.8.Servlet-info in web configuration file 3.2.9.servlet resource-access


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Servlets are initialized via an init( ) method at thetime of Instantiation

The init( ) method is called only once during thelifecycle of the Servlet, so, it need not be written

as Thread-Safe The init( ) method is used for

Storing its Configuration parameters

Initializing the values of Servlet members

Loading JDBC Database Drivers

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After initialization, its service( ) method is calledfor every request to the Servlet

The service( ) method is called concurrently (i.e.multiple threads may call this method at the

same time) The service( ) method should be implemented in

a Thread-safe manner

The service( ) method usually contains the bulkof the business logic

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Servlets run until they are removed from theservice (Un-loading / Shutting down)

The destroy( ) method is invoked for performingclean up activities

The destroy( ) method is called only once, but,since other threads might be running service( )methods when destroy( ) is invoked, it needs to

be implemented in a Thread-

Safe manner

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3.2.Servlets






3.2.7.HTTP Servlet Cookies

3.2.8.servlet-info in web configuration file 3.2.9.servlet resource-access


3 2 3 S l S l

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A client makes a Request to a server The request is resolved to a HTTP Servlet by the

Servlet Engine

The HTTP Servlet receive relevant inputs fromthe WEB Browser (all the HTML Form elementsand their values)

HTTP Servlets responds a HTML Page back to the

Browser

3 2 3 A S l HTTP S l

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The following HTML Page accepts your Nameand submits a request to a Servlet named

HelloWorldServlet present in your PC:

Enter Your Name :

3 2 3 A S l HTTP S l t

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The code for HelloWorldServlet.java looks like this:import java.io.*;import javax.servlet.*;

import javax.servlet.http.*;

public class HelloWorldServlet extends HttpServlet {

String companyName;

public void init( ServletConfig config ) throws ServletException {

super.init( config );

companyName = getInitParameter( company );

if ( companyName == null ) {

throw new UnavailableException( this,Un-Authorized );

}

} //End of init( ) method

public void destroy( ) {

companyName = null;

} //End of Destroy( ) method

3 2 3 A S l HTTP S l t

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protected void doGet( HttpServletRequest req,HttpServletResponse res )

throws ServletException, IOException {

res.setContentType( text/html );

PrintWriter out = res.getWriter( );

out.println( Hello World!! +By + req.getParameter( USER ) +

of + companyName +

);

out.close( );

} //End of service( ) method

} // End of Hello World Servlet

3 2 S l t

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3.2.Servlets




3.2.4.HTTP Servlet - Anatomy

3.2.5.HTTP Servlet- Session Management 3.2.6.ServletContext and ServletConfig



3.2.9.servlet resource-access 3.2.9.1.filter,filter-mappings

3 2 4 HTTP S l t A t

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Hello World Servlet- Import Lines 1 to 3 import packages which contain classes

that are used by the Servlet

import java.io.*;

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

javax is an extended Java packages library

javax.servlet.http contains all classes used by HTTP

Servlets


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Hello World Servlet- Declaration The Servlet class is declared as extends

javax.servlet.http.HttpServlet

public class HelloWorldServlet

extends HttpServlet This declaration is necessary for Request / Response

interaction with the WEB Browser using HTTP Protocol

The HttpServlet is an abstract class which extends

the GenericServlet class


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Hello World Servlet- init( ) The init( ) method is overridden for the purpose of

initializing the Servlet

public void init( ServletConfig config )

throws ServletException {super.init( config );

...

}

3 2 4 HTTP Se let Anatom

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Hello World Servlet- init( ) In init( ) we first call super.init( config ) to leave the

ServletConfig management to the superclass(HttpServlet)

If the servlet's required resources can not be madeavailable (a required network connection can not beestablished), or some other initialization error occurs,an UnavailableException is thrown

The UnavailableException extends ServletException

3 2 4 HTTP Servlet Anatomy

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Hello World Servlet- init( ) In this init( ) method, we are getting an Initialization

parameter called company from the Servletsconfiguration file(web.xml) and assigning its value to a

member called companyName Version 2.1 of the Servlet API offers an no-args init( )

method which is called by GenericServlet'sinit(ServletConfig) method

It is not mandatory to include the init( ), but, is goodpractice to do so


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Hello World Servlet- destroy( ) The destroy( ) method is overridden for clean-up

during unloading of Servlets

public void destroy( ) {

companyName = null;}

In this destroy( ) we are marking the Servlet membercalled companyName for garbage collection

It is not mandatory to include the destroy( ), but isgood practice to do so


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Hello World Servlet- service( ) The service( ) method is overridden for Request /

Response interaction with the client browser

protected void service( HttpServletRequest req,

HttpServletResponse res )throws ServletException, IOException {

.

}

The service( ) method is invoked by the Servlet Enginefor each client request


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Hello World Servlet-

service( ) A separate Thread is spawned by the Servlet Engine toservice each request

The service( ) method is invoked implicitly by thecontainer to call either call doGet/doPost that issuitable for the given request

The doGet( ) and the doPost( ) methods should only tobe used in place of service( ) method wheneversubclasses of HttpServlet are designed

There 6 methods likedoPut(),doDelete(),doTrace(),doOptions(),doPost(),doGet() matching to the type of http requests,all ofwhich are called service methods


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Hello World Servlet- service( )

The service methods have following parameters:

HttpServletRequest

for abstracting the request from the client

provides access to HTTP header data, such as any cookies

found in the request provides access to all request parameters,attributes as

name/value pairs

HttpServletResponse

for responding HTML pages back to the client

Contains Handle of the Output Stream / Writer to theClient Browser

For redirecting to an another URL


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Hello World Servlet- service( )

We are getting the value of a Request parametercalled USER using the getParameter( ) method of the

HttpServletRequest object

We are using the above value and thecompanyName obtained from the init( ) method to

form the Dynamic HTML page as a response


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Hello World Servlet doGet() method We are accessing the HTTP Header to set the content

type of the Response, using the setContentType( )method of the HttpServletResponse object

For HTTP response, We are getting a PrintWriterObject using the getWriter( ) method of theHttpServletResponse object

We are using the println( ) method of the PrintWriter

Object to write HTML information on to the ClientBrowser

3 2 Servlets

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3.2.Servlets

3.2.1

.Introduction to Servlets 3.2.2.Life Cycle of Servlets



3.2.5.HTTP Servlet - Session Management 3.2.6.ServletContext and ServletConfig




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3.2.5.HTTP Servlet-Session Management

Session Management is the process ofmaintaining persistence and State Information

Session Management is required because HTTP isby default, stateless

Session Management is easily used for UserAuthentication across requests within the samesession

Session Management is used for Caching re-usable information

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A Session consists of An unique Session ID which travels back and forth between the

Client and the Server. The Session ID is used to map a request toa particular Client Session

A Session Context area in the Server for storing general and

application information pertaining to the Client Session In HTTP Servlets, the Session can be maintained and

tracked by four methods

cookies

URL-rewriting Hidden fields

Session-tracking

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In session tracking,HttpSession defines methodswhich can extract the following types of data:

Standard session properties, such as an identifier forthe session, authenticity of the session and the context

for the session Application layer data stored using a dictionary-like

interface

Using getAttribute(),setAttribute() clients specific data

can be stored or retrieved

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The following code snippets describeSession authentication and Caching:

Session Creation (after User Login):HttpSession session = req.getSession( true );

session.setAttribute( USER , req.getParameter( USER )* );* any value as an object

Session Authentication (each request):HttpSession session = req.getSession( false );

if ( ( session == null ) || ( session.isNew( ) ) ) {

res.sendRedirect( loginURL );

}

String userId = session.getAttribute( USER );

3 2 Servlets

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3.2.Servlets

3.2.1








3 2 6 ServletContext and ServletConfig

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The ServletContext and the ServletConfiginterfaces of javax.servlet package are used for

getting the server environment information

getting servlets initialization parameters

passing configuration information to the servlet engine

logging Events

accessing a other servlet deployed in the samecontainer

3 2 6 ServletContext and ServletConfig

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The following code snippet describe externalAccess of a Servlets members:RequestDispatcher rd = this.getServletContext().getRequestDispatcher(/servlet/other );

rd.forward(request,response);

first, the ServletContext is obtained from theservlet itself and then a handle to the externalServlet is obtained from this ServletContext asan Object of RequestDispatcher

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3.2.Servlets

3.2.1





3.2.7.HTTP Servlet - Cookies



3 2 7 HTTP Servlet - Cookies

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Cookies are very useful in maintaining statevariables on the WEB

A cookie is simply a text-file that consists of atext-only string which gets stored and maintained

by the browser Cookies are unique named, and have a singlevalue with settable life(with optional attributes,including comment, path and domain qualifiersfor the hosts which see the cookie, a maximumage, and a version)

3 2 7 HTTP Servlet - Cookies

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Cookies can be passed back and forth between

the browser and the server Cookies are created on the instruction of a web-

server

After a cookie is transmitted through the HTTPheader, it is kept at the browser for fast retrievalso that any request that goes to the sameserver,the browser will attach all live coockies of

that server along with the request Cookies are by default have a life spanning to

clients session


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Browser settings allow rejection of Cookies, so,the programmer needs to be careful in the usageof Cookies

Applications that use cookies include:

Storing user preferences

Personalization

Automating low security user sign-on

Collecting data used for "shopping cart" styleapplications


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Cookies can be set and retrieved at Client-sideusing JavaScript / VBScript

HTTP Servlets support setting, retrieval andmanipulation of Cookies as follows :

The addCookie( ) method of the HttpServletResponse -for setting Cookies

The getCookies( ) method of the HttpServletRequest-for retrieving Cookies

The javax.servlet.http.Cookie class - for creating andmanipulating Cookies


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The following code snippets describe theusage of Cookies in HTTP Servlets: Cookie Creation:

Cookie toClient1 = new Cookie( USER,SHIVA );

res.addCookie( toClient1

);Cookie toClient2 = new Cookie( COMP,HTC );res.addCookie( toClient2 );

Cookie Retrieval:Cookie[ ] fromClient = req.getCookies( );

for ( int i = 0; i < fromClient.length; i++ ) {System.out.println( Cookie + fromClient[ i ].getName( ) + Has Value : + fromClient[ i ].getValue( ) );

}

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3.2.Servlets





3.2.5.HTTP Servlet-

Session Management 3.2.6.ServletContext and ServletConfig


3.2.8.Servlet -info in web configuration file


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3.2.8.Sevlet Configuration file

Servlets all deployment information is made available tothe container in the web configuration file web.xml.thefollowing are the important elements in this regard

..

..

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..

/

..

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1800

..

..

3.2.Servlets

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- 3.2.1.Introduction to Servlets




3.2.6.ServletContext and ServletConfig 3.2.7.HTTP Servlet- Cookies




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3.2.9.servlet resource access

Any other resources that are there on the applicationserver can easily be accessed by the servlet through ENC(Environment Naming Context)in similar way as EJBs

resource is defined in web.xml file as

*

.

.

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3.2.9.servlet resource access

This is referred and accessed in servlet code fromthe jndi InitialContext object as

InitialContext ctx=new InitialContext();resource-type-classobj=ctx.lookup(java:comp/env/*);

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- 3.2.1.Introduction to Servlets




3.2.6.ServletContext and ServletConfig 3.2.7.HTTP Servlet- Cookies




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A Filter can perform filtering on clients request for aresource like a servlet/static content or on a response thatgoes from a resource.they are majorly used forauthentiction,logging,auditing,xml based

transformations,to fire events.. Any class that implement Filter interface have to give codefor the following methods

init(FilterConfig ..) destroy()

doFilter(ServletRequest req,ServletResponse res,FilterChain ..) It is in the doFilter() method ,the filter will be doing its

aimed task.The filterchain object can be used chainedfilters

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The FilterConfig object allows the Filter class toaccess any of the configured initial parametersthat can be given in web.xml within tag

The associated methods are getInitParameterNames() getInitParameter()

getServletContext()

filter-

mappings are given in web.xml file to tellthe container what filters are there for therequested uri and in what order

3 2 JSP

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3.2.JSPWhat do JSPs contain?

Java Server Pages are text files that combine standardHTML/XML and new scripting tags

JSPs look like HTML/XML ,but they got compiled into Javaservlets the first time they are invoked

The resulting servlet is a combination of the HTML fromthe JSP file and embedded dynamic content specified bythe new tags

Everything in a JSP page can be broken into 2 categories:

Elements that are processed on the server

Template data ,or everything other than elements,that the engine processing the JSP ignores

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JSP Life Cycle:-

Intialize

public void jspInit()

|

handle client request s and generate responses

void_jspService(ServletRequest,ServletResponse)throwsIOException,ServletException

|

Destory

public void jspDestory()

3 2 JSP

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3.2.JSP

Directives Declarations

Scriptlets

Expressions

Standard actions

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3.2.JSP -Directive

The three directives are:- page directive

include directive

taglib directive

page directive:- defines a number of important attributes that

affect the whole page A single JSP can contain multiple page directives,

and during translation all the page ditectives are

assimilated (integrated) and applied to the samepage together

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various attributes of page directive are:- language

extends

import session

buffer autoFlush

isThreadSafe

info

isErrorPage errorPage contentType

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3.2.JSP Directives

include directive It notifies the container to include the content of the resource in

the current JSP ,inline, at the specified place.

The content of the included file is parsed by the JSP and thishappens only at translation time.

The included file should not be another dynamic page.

Most JSP containers usually keep track of the included file andrecompile the JSP if it changes

Atttibute:-

file (the static filename to include)

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taglib directive allows the page to use custom user defined tags

it also names the tag library that they are defined in

The engine uses this tag library to find out what to do when itcomes across the custom tags in the JSP

Attributes are:-

uri

prefix

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Scripting elements are used to include scripting

code(usually java code) within the JSP.

They allow you to declare variables and methods

The three types of scripting elements are: Declarations

Scriptlets

Expressions

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A declaration is a block of java code in a JSP that is

used to define class-wide variables and methods They are initialized when the JSP page is initialized Can not produce output to client

Ex:-

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A Scriptlet is a block of java code that isexecuted at request-processing time

Can produce output to the client

ex:-

3 2 JSP - Expressions

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3.2.JSP Expressions

Expressions are to display any user output or a

manipulated value When the expression is evaluated ,the result is

converted to a string and displayed

Ex:-

3.2.JSP Standard Actions

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Actions are specific tags that affect the runtime

behaviour of the JSP and affect the response sent backto the client Standard Action types are:-

Use Bean Set Property

Get Property

Param Params

Include

Forward Plug-in

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Jsp:useBean

Is used to associate a javaBean with the JSP

JSP:setProperty

Is used in conjunction with the useBean action

To set the value of the properties of a bean Jsp:getProperty

Is used in conjunction with the useBean action

Complementary to the JSP:setProperty

To access the properties of a bean

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jsp:param used to provide other tags with additional information in the

form of name value pairs

used in conjunction with jsp:include,jsp:forward and jsp:pluginactions

Jsp:include Allows a static or dynamic resource to be included in the currentJSP at request time

Jsp:forward Allows the request to be forwarded to another JSP,a servlet

Jsp:plugin Meant to dynamically load the browsers plugin jdk software

either to run an applet or gui-bean

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These objects do not be declared or instantiated by the JSPauthor, but are provided by the container in the implementationclass

All the implicit objects are available only to scriptlets ordeclarations , and are not available in declarations

Different implicit objects are:- request object

response object

pageContext object

session object

application object

Out object

config object

page object

exception object

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Expressions appear between ${ and }. Note that${ and } may contain whole expressions,

not just variable names, as in the Bourne shell (and itsdozen derivatives.)

E.g., ${myExpression + 2}

Expressions default targets are scopedattributes (page, request, session,application)

${duck} pageContext.findAttribute(duck)

3.2.JSP 2.0 EL

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J

The . and [] operators refer to JavaBean-style

properties and Map elements: ${duck.beakColor} can resolve to

((Duck)

pageContext.getAttribute(duck)).getBeakColor()

Note the automatic type-cast. This is one of the great features of the EL: users do not need to concernthemselves with types in most cases (even though the underlying typesof data objects are preserved.)

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J 0

Expressions may also refer to cookies, requestparameters, and other data: ${cookie.crumb}

${param.password}

${header[User-Agent]}

${pageContext.request.remoteUser}

3.2.JSP 2.0 EL

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J

The EL supports Arithmetic ${age + 3}

Comparisons ${age > 21}

Equality checks ${age = 55}

Logical operations ${young or beautiful} Emptiness detection ${empty a}

a is empty String (), empty List, null, etc. Usefulfor ${empty param.x}


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J

3.1.JDBC

3.2.Servlets & JSP

3.3.Tag Libraries 3.4.Struts

3.5.Struts-Tag Libraries 3.6.JSTL

3.7.XML

3.8.Junit

3.9.Ant

3.3.Tag Libraries Introduction

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g

Tag (often referred as custom tags) look like

HTML/XML tags embedded in a JSP page They have a special meaning to a JSP engine at

translation time, and enable applicationfunctionality to be invoked without the need towrite the java code in JSP scriptlets

It is used to encapsulate java functionality thatcan be used from a JSP page

Well-designed tag libraries can enable applicationfunctionality to be invoked without theappearance of programming

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Types of tag Predefined Tag

Customized Tag

Predefined Tag

Functionality provided implicitly by container. Example

3.3.Tag Libraries

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Customized Tag Functionality provided by the programer.

Example

The above codes connects to a database and get theproduct list.

Advantage The web page developer can concentrate on the

content rather than business logic. Access to implicit object.(details later)

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Any valid custom tag should contain : A reference in Tag Library Descriptor

A Tag Handler Class

Tag Handler

Its the class which provides the javafunctionality for that particular tag.

Tag Library Descriptor

Contains various Tags

Links Tags with Handler Classes

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What is a TLD (Tag Library Descriptor) ? A XML file which contains list of tags and information

about them.

Information contains

Name of Handler class

About the nature of tag (details later)

can contain many tag

(no 1 to 1 mapping between tag and TLD)

Saved with .tld extension

Contains also information about attributes

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Types of Tag:-- Simple Tag (No Body,No Attribute).

Simple Tag With Attributes.

Tag With Body.

Nested Tag.

3.3.Tag Libraries-Simple tag

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g p g

A simple tag is without attributes or tag bodies

They are of the form

Example:- HelloWorld.jsp

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g p g

Tag Handler Classpublic class HelloWorld extends SimpleTagSupport

{

public void doTag() throws JspTagException

{ // this method is called when the start is encounteredpageContext.getOut.write("Hello World");

// pageContext is object provided by container through

// implicit objects can be created and used.

}

}

HelloWorld.java

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Tag Library Descriptor :---

sayHello // Name of the Tag used in JspHelloWorld // Name of Tag Handler Clempty

TagCollection.tld

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Adds flexibility to your tag library

Allowing tags like

Example:--

AttribTag.jsp

3.3.Tag Libraries- Tags with attribute

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import javax.servlet.http.*;

import javax.servlet.jsp.*;import javax.servlet.jsp.tagext.*;

import java.io.*;public class TagAttrib extends SimpleTagSupport {

private String name;public setName(String name) {

this.name=name;

}public void doTag()throws JspTagException {

pageContext.getOut.write("Hello "+ name);}

}

TagAttrib.java

3.3.Tag Libraries- Tags with attribute

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inputTagAttrib

nametruetrue

empty

TagCollections.tld

3.3.Tag Libraries -Tag with Body

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This tag is used in the following manner

body

Example:--

This is a Body Tag // Content can be

Jsp,HTML. The Handler class implement BodyTag

interface.Support class is BodyTagSupport. You have additional methods

doAfterBody(),doInitBody() in Tag class

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Example:--Hello.jsp

Untitled

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The TagHandler class extends BodyTagSupport {setPageContext(){} // container sets thepagecontextsetParent()// sets the parent in case of nested tag

set the attributes using setMethodsdoStartTag()// Executed when the starting tag is

encountered should return EVAL_BODY_TAGsetBodyContent()// to set the current BodyContentfor it to use (if there is at least one evaluation of thebody of the BodyTag).

doInitBody() // This is where we will normally put anyinstructions that should be taken care of before thebody of the BodyTag is evaluated for the first time.


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doAfterBody() // called after each evaluation of thebody.If this method returns EVAL_BODY_TAG, thismethod should be called again. If this methodreturns SKIP_BODY, continue below.

doEndTag()//called when the ending tag isencountered.

release()

}


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Tag Handler classpackage htc;

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

public class HelloWithBody extends BodyTagSupport{

public int count;int i;public void setCount(int count)

{this.count = count;

}


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public int doAfterBody() throws JspTagException{

i++;String msg = getBodyContent().getString();try{getBodyContent().getEnclosingWriter().write(msg);}

catch(Exception e) { }getBodyContent().clearBody();if(i>=count)

return SKIP_BODY;else

return EVAL_BODY_TAG;}

}


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Tag Library Descriptor File

HelloWithBodyhtc.HelloWithBodyJSP

counttruefalse

3.3.Tag Libraries-Nested Tags

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Nested tags are nothing but a tag used inside

another tag Where the behaviour of certain tags depends on

values supplied by earlier tags ,we go for nestedtags

To define a tag that depend on a particularnesting order For ex:-in standard HTML, the TD and TH elements

can only appear within TR, which in turn can only

appear within TABLE


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Tag Handler Classes

Can be extended from either TagSupport orBodyTagSupport, depending on whether they need tomanipulate their body content(these extendBodyTagSupport ) or just ignore it(these extend

TagSupport ) There are two new approaches for nested tags

First, nested tags can use findAncestorWithClass to findthe instance of a given class type that is closest to a

given instance.


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First (continued):--

this method takes a reference to the current class(e.g.this) and the Class object of the enclosing class(e.g.EnclosingTag.class) as arguments

If no enclosing class is found , the method in the nestedclass can throw a JspTagException that reports theproblem

Second :-- if one tag wants to store data that a later tag will use,

it can place that data in the instance of the enclosing tag

The definition of the enclosing tag should providemethods for storing and accessing this data

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The IterationTag interface extends Tag by defining oneadditional method that controls the reevaluation of its body.

A tag handler that implements IterationTag is treated as onethat implements Tag regarding the doStartTag() anddoEndTag() methods. IterationTag provides a new method:doAfterBody().

The doAfterBody() method is invoked after every bodyevaluation to control whether the body will be reevaluated ornot.

If doAfterBody() returns IterationTag.EVAL_BODY_AGAIN,

then the body will be reevaluated. If doAfterBody() returnsTag.SKIP_BODY, then the body will be skipped anddoEndTag() will be evaluated instead.

3.3.Tag Libraries-Tag Extra Info Classes

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Optional class provided by the tag library author todescribe additional translation-time information notdescribed in the TLD

This class can be used: to indicate that the tag defines scripting variables

to perform translation-time validation of the tag attributes

To extend from Tag Extra Info class ,you have to overridetwo methods VariableInfo[ ] getVariableInfo(TagData data)

Used to return information on scripting variables that the tagmakesavailable to JSPs using it

Returns an array ofVariableInfo objects, which contain informationabout the name of each scripting variable and its fully qualifiedclass name

3.3.Tag Libraries-Tag Validation

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3.3.Tag Libraries-Tag Extra Info Classes

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boolean isValid(TagData data)

used for Translation-time validation of theattributes.

Request-time attributes are indicated as such inthe TagData parameter.


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3.1.JDBC 3.2.Servlets & JSP

3.3.Tag Libraries 3.4.Struts


3.7.XML

3.8.Junit

3.9.Ant

3.4.Struts

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Framework

set of multiple classes,interfaces,components aimed at solvingspecific problem/application

reusable

utilizes J2EE patterns while building the components in particular

Struts is such a framework mainly created by Craig R.

McClanahan and donated to ASF in 2000. Struts match to MVC2 patterns where the controller will

mostly forward to different urls based on the clientsrequest w/o sending any response which is totally

handled by view component i.e jsps

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Struts is made up of approximately 300 java classesdivided into 8 core packages like actions contain Action Classes action contain controller classes like ActionForm,ActionMessages util contain general-purpose utility classes taglib contain tag handler libraries

upload contain classes that help uploading and downloading files

through a browser tiles contain classes meant for tiles framework config contain configuration classes whose objects gets initialized

from the struts-config.xml contents validator contain Struts specific extension classes meant for of

validator.actual validator classes are available in the commonspackage,separate from struts

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In struts framework the Controller component functionalityis divided by more than one component,one of which isorg.apache.struts.action.ActionServlet class whose mainfunction is to receive the clients request and process itthrough a handler class i.e RequestProcessor class in 1.1version,meant for flexibility to subclass.after this itdelegates the handling of the request to a helper class

which is a subclass of org.apache.struts.action.Action sothat decoupling client-request & business-logic takes place.

Subclasses of Action class should give code forpublic ActionForwardexecute(ActionMapping,ActionForm,HttpServletRequest,HttpServletResponse) as the framework creates a singleton ofthis and invoke its execute method since the super classthe method returns null.

3.4.Struts

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the ActionServlet class will be configured in

web.xml which is the single one that will invokesuitable action Objects as per the input form theimportant initial parameters for this servlet are configlocation of struts-config.xml file

config/sub to specify additional configuration files

debugcontrols how much info is to be logged detaildetail level for Digestor,which logs info as it

parses the configuration files convertHacka boolean variable whether any Wrapper

class variables are to be initialized to null(if true defaultis false) or default value of their type

3.4.Struts

h i l ill b fi d i

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the Action class will be configured in

struts-

config.xml within blocksas action element with following importantattributes attributename of session-scope attribute under which

form-bean can be accessed

classNamethe implementation class,by defaultActionMapping

forwardthe application-relative path to a resource towhich further navigation occur.the attributesforward/include/type are mutually exclusive

Input application-relative path of the input form towhich control should go if a validation error occur

3.4.Struts

th f th f b i t d ith thi

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namethe name of the form-bean associated with thisaction.this value should one of name attribute of theform-bean elements defined already

paththe application-relative path to the submittedrequest,starting with / character

parameter to take care of any extra information that is

required so that action class can use getParameter()method scope request or session to identify the scope of the

associated form-bean typefully qualified javaclass name

validatedetermines whether validate() method isinvoked by the form-bean or not default is true

3.4.Struts

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Types of Action classes

Dispatch Actions mean for abstracting multiple actionsin a single class instead of scattering over multipleaction classes useful particularly when actions arerelated and focussed on an entity like sale ofproduct,updation of its price,viewing the details of it

typical implementation as many named methods thatreturn suitable ActionForward object.the configurationcontains parameter attribute with method and methodname is used in the url like

http://localhost:8080/myappl/sales?method=sellProduct

3.4.Struts

T f A ti l

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Forard Actions

useful where the controller will simplyforward from one jsp page to another jsp page withoutspecific processing by Action class no specifical Actionclass writing is necessary.the type attribute will beorg.apache.struts.actions.ForwardAction and the

forwarding target url is given by the parameter attribute Include Actions originally planned to integrate servlet-based components into struts-based webapplications.type attribute will haveorg.apache.struts.actions.IncludeAction and the url is

given by the parameter attribute

3.4.Struts

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Switch Actions this is intended to support switchingfrom one application-module to another particularlywhen you can configure more than one configuration filerequires a prefix request parameter that gives the

application prefix.if wanted to switch to the default ,youcan use zero-length string as .the page requestparameter should be there that gives the relative path.Only required if you have more than one module.Thetype is org.apache.struts.actions.SwitchAction

3.4.Struts

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Form-Beans

these are meant to take care of storing the users giveninput data and transfer them to the Action/subclasses(inexecute method)validating the input and display errors incase of validation failure.these are written as extending

ActionForm class.

These can have two levels of scope requestform-bean is available till the response is returned

to the client

sessionnecessary if application captures data across

multiple pages and will be there till the session is timed out

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these are created as subclasses of ActionForm(which isabstract) to capture an application-specific form-data.withinthe class you should define a property for each field that isgoing to be received through the html form with accessor &mutator methods.it may contain a validate() method whichRequestProcessor class calls as well as reset() method,sincethe reset method is called for every new request particularyif default scope ie session is in effect,so that the bean fieldsare set back to their defaults.

These are configured under form-bean element underform-beans element,contains two required attributesa)name should match to that of action elementsb)type should have full packaged path of form class

3.4.Struts

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Dynamic ActionForms will avoid exclusive writing of

subclasses as you can configure the simple properties inconfiguration file itself for ex

But if validate method is to be implementation,another classhas to be written only for that,since by default reset(0method is taken well care of

3.4.Struts

Struts Validator

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Struts Validatorstruts framework allows to skip validation in actionforms

and done through David winterfeldts validatorframework.this will allow to configure.the framework rulesare available in validator-rules.xml the other file isvalidation.xml which is application-specific as it describeswhich validation rules from the above xml file are beingused by the application for ex:

.

3.4.Struts

Struts Validator

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Struts Validator

all the above ,we can call as server-sidevalidation.for client-side validation you can usecustomTag called JavascriptValidator based onthe javascript code available in validator-rules.xml

when the JavascriptValidator is used in the jsp filethe text from the javascript element is madeavailable to the jsp page allowing client-sidevalidation there should be in the jsp

3.Advanced-Java Contents-1

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3.1.JDBC 3.2.Servlets & JSP

3.3.Tag Libraries

3.4.Struts


3.7.XML

3.8.Junit

3.9.Ant

3.5.Struts-Tag Libraries

>The struts framework provides a fairly rich set of

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->The struts framework provides a fairly rich set of

framework components->It also includes a set of tag libraries that aredesigned to interact intimately with the rest of theframework

-

>The custom tags provided by struts are groupedinto:-HTML TagsBean Tags

Logic Tags

Nested TagsTiles Tags

3.5.Struts-Tag Libs-HTML tag

C t i t g d t t HTML i t f

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Contains tags used to create HTML input forms

For ex:-instead of using a regular HTML text-input field ,you can use the text tag from thislibrary

These tags are designed to work with the other

components of the Struts framework,includingActionForms

Most of the tags within this library must benested inside of a Struts form tag


Custom tags within the Struts HTML tag

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g gLibrary are:-

< html:button/>

< html:checkbox/>

< html:file/>

< html:hidden/>

< html:image/>


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Custom tags within the Struts HTML tag Library

are (continued):- < html:link/> < html:option/>

< html:password/> < html:reset/>

< html:submit/> < html:textarea/>


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Used to insert an HTML element ,including an

href pointing to the absolute location of the hostingJSP page

Has no body and supports two attributes(optional)

Used to render an HTML element with an

input type of button

Has a body type of JSP

Required attribute are: property,title


ht l l /

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Used to render an HTML element with an inputtype of cancel

Has a body type of JSP and supports 25 attributes

Required attributes are:- title

Used to render an HTML element with an input

type of checkbox


Required attributes are:- property,title Must be nested inside the body of an tag


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Used to display the ActionError objects stored in anActionErrors collection

Has a body type of JSP and supports fourattributes(optional)

Used to create an HTML element Allows you to upload files

Has a body tag of JSP and supports 30 attributes

Required attributes are:- property,title Must be nested inside the body of an tag


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Used to create an HTML form has a body type of JSP and supports 13 attributes

Required attributes are :- action

Used to render an HTML element with an input typeof hidden

Has a body of JSP and supports 25 attributes

Required attributes are :- property,title

Must be nested inside the body of antag


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Used to insert an custom JavaScript validation methods

has no body and supports 8 attributes

No required attributes are there

Used to generate an HTML hyperlink Has a body type of JSP and supports 37 attributes

Required attributes are :- title


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Used to display a general-

purpose messages to theuser stored in ActionMessages,ActionErrors etc

has a body type of JSP and supports 8 attributes

Required attributes are :- id

Used to generate an HTML element of

type, which represents a single optionelement nested inside a parent element

Has a body type of JSP and supports 8 attributes Required attributes are :- value


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p / Used to generate a list of HTMLelements

Child of the tag

has no body and supports 8 attributes

Required attributes are :- action

Must be nested inside antag

Can also be used n-

number of times within an html:select/>element

Used to render an HTML element with an input type ofpassword


Required attributes are :- property,title Must be nested inside the body of antag


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Used to render an HTMLelement with an inputtype of radio

has a body of type JSP and supports 28 attributes

No required attributes are :-property, value, title

Must be nested inside antag


type of reset

Has a body type of JSP and supports 25 attributes No required attributes are there


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Used to render an HTMLelement with an input

type of select


No Required attributes are there


type of image


Required attributes are :- title



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Used to render the top-levelelement


Required attributes are :- property, title



type of submit, which results in a Submit button


No Required attributes are there Must be nested inside the body of antag


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Used to render an HTML element with an inputtype of text


Required attributes are :- property, title



type of textarea

Has a body of type JSP and supports 30 attributes Required attributes are :- property, title


3.5.Struts Tag Libs-Bean tag

Bean Tag library provides a group of tags that

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g b y p s g p gsencapsulates the logic necessary to access andmanipulate JavaBeans,HTTP cookies and HTTPheaders using scripting variables

There are currently 11 custom tags in the Bean

tag library Custom tags are:-


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Custom tags are:- (continued)

< bean:message/>


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Used to retrieve the value of an HTTP cookie

Can be used to retrieve single or multiple cookie values It has no body and supports 4 attributes Required attributes are :- id , name

Used to retrieve the value of a named bean property anddefine it as a scripting variable,which will be stored in thescope specified by the toScope attribute

It has a body type of JSP and supports 7 attributes

Required attributes are :-

id


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It functions exactly like except that itretrieves its values from the named request header

It has a body type of JSP and supports 4 attributes

Required attributes are:- id, name

Used to evaluate and retrieve the results of a Web

application resource

The tag functions much like the

standard action, except that the response is stored ina page scoped object attribute, as opposed to beingwritten to the output stream

3.5.Struts Tag Libs -Bean tag

b

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Used to retrieve the value of an identified implicit

JSP object, which it stores in the page context ofthe current JSP

The retrieved object will be stored in the page

scoped scripting variable named by the id attribute Has no body and supports 2 attributes

Required attributes are :- id, property

For ex:-

We are retrieving the implicit session object and storing

this reference in the scripting variable sessionVar


b /

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Used to retrieve the value of a request parameter

identified by the name attribute

The retrieved value will be used to define a pagescoped attribute of type String or String[], if the

multiple value is not null Has no body and supports 4 attributes

Required attributes are :- id, name

For ex:-


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Used to retrieve the value of Web applicationresource identified by the name attribute

Has no body and supports 3 attributes

Required attributes are :- id, name

Used to retrieve the number of elements containedin a reference to an array, collection,or map

Has no body and supports 5 attributes

Required attributes are:-

id

3.5.Struts Tag Libs -Logic tag

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Contains tags that are useful for managingconditional genaration of output text, looping overobject collections for repetitive generation ofouput text, and application flow management

So the focus of the logic tag library is on decisionmaking and object evaluation

Logic tag library contains:-

3.5.Struts Tag Libs -Logic tag Logic tag library contains (coninued)

l i f d /

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Page 173Presentation Name

HTC Confidential


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Evaluates its body if either the scripting variable identifiedby the name attribute or a property of the named scriptingvariable is equal to null or an empty string


Required attributes are:- name

Ex:--

We test the scripting variable user .if this variable is null oran empty string , then the body will be evaluated, which

will result in the user being forwarded to the globalforward login


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HTC Confidential

g p y it is just opposite of tag

Evaluates its body if either the variable specified by any one

of the attributes cookie, name, parameter, or propertyequals the constant value specified by the value attribute


Required attributes are:- value Ex:-- You are exactly the right age.

We test the age data member of the scripting variable

user.If this data member equals the value stored in therequiredAge variable, then the tags body will be evaluated


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HTC Confidential

it is just opposite of tag

Used to forward control of the current request to a

previously identified global forward element

Has no body and supports a single attribute name, which

identifies the name of the global element that will receivecontrol of the request

Ex:-

We forward the current request to the global forwardlogin


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HTC Confidential

uses the HttpServletResponse.sendRedirect()method to redirect the cuttent request to aresource identified by either the forward,href ,orpage attributes

Has no body and supports 12 attributes (optional)

Evaluates its body if the variable specified by any

one of the attributes cookie, name,parameter, orproperty is greater than or equal to the constant

value specified by the value attribute Has a body type of JSP and supports 7 attributes

Required attributes are :- value, name


l i t Th /

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Simmilar to tag

Used to iterate over a named collection and evaluatesits body for each Object in the collection


Requred attributes are:-

id


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Evaluates its body if the variable contains thespecified constant value


Required attributes are :- value

tag is just opposite of match

tag

Evaluates its body if the variable specified ispresent in the application scope

Has a body type of JSP and supports 8 attributes(optional) tag is just opposite of present

tag

3.5.Struts Tag Libs -Nested tag

In nested tags you can use one tag inside

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HTC Confidential

In nested tags you can use one tag inside

another tag that belong to thehtml,bean,logic groups with little confusionwith the necessity of making the child elementaware of the parent element

3.5.Struts Tag Libs -Tiles tag

The tiles tag library give page designers a

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