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The EJB specification provides Enterprise-level services. Typical services

provided by the EJB Container are as follows.

1.Persistence

2.Declarative transactions

3.Security

4.Connection pooling

5.Support for messaging services

The most famous EJB-Servers in the market are:

y BEA ..WebLogic Servery JBoss Application servery IBM.WebSphere-5y Oracle AS

Of these , JBoss 3.2 & 4 are OpenSource and Free However, BEA has the

longest record and used by many enterprises and hence a standard..Therefore, I am

now writing about WebLogic-7 and later, I will cover JBoss3.2 in a separate

lesson.( The latest version of Weblogic is WL-9).

Different kinds of Enterprise Beans are

1. Session Bean

2. Entity Bean

3. MessageDriven Bean (MDB)

Session Bean

Session Bean can be defined as function bean called in RMI-IIOP style from

Enterprise container. Two types of session bean are stateless session

bean, stateful session bean.

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A stateless session bean does not maintain conversation state but stateful session

bean maintains conversation state

Entity Bean

Entity Bean is a value bean with setter and getter methods representing one row

of data in a table, invoked in RMI style from Enterprise container in Enterprise

data store. Two types of Entity Beans areCMP (Container Managed

Persistence), BMP (Bean Managed Persistence). In CMP, persistence code need

not be written by the programmer. But In BMP Persistence code has to be written

by the programmer .CMP is not satisfactory for really complex enterprise

situations. ( CMP is an ORM technology ( Object-Relational Mapping Technology

like Hibernate. and Hibernate is considered to be better than CMP).

Message Driven Bean

Session Bean and Entity bean are based on RPC mechanism. But,

Message Driven Bean is based on Asynchronous messaging . MDB have no

conversational state with the client and can be pooled like stateless session bean.

Unlike other types of EJB, MDB have no home or remote interfaces.

Messaging is like email whereas RPC is like phone call. In enterprise environmentthere will be heavy traffic and RPC may fail to create connection. In such

situations messaging is more reliable.

What is Struts?

Struts is a very famous ready made framework which implements MVC (Model

View Controller) Architecture. It is open source and free. Struts frame work was

developed by Craig MacLanahan in 2002 subsequently handed over to Apache

Jakarta projects group. Struts is a frame work for building really complexEnterprise level applications

Struts provide its own Controller component and integrates with other technologies

to provide the Model and the View. For the Model, Struts can interact with

standard data access technologies, like JDBC and EJB, as well as most any third-

party packages, like Hibernate, iBATIS, orObject Relational Bridge. For the

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View, Struts works well with JavaServer Pages, including JSTL and JSF, as well

as Velocity Templates, XSLT, and other presentation systems

Purpose of the Struts

When the user fills the form and submits the form, if the values entered by the user

are wrong then the user must be presented with the same page with suitable error

messages and the values already entered by the user should be preserved.

If there is no error, ( validation test is passed), then the business logic is executed..

Installation

Struts1.1 is zip file. Extract it. In Struts1.1 folder, there is a folder name called lib.

There are many war files. One of the war file names, is struts-blank.war. Copy

that struts-blank.war file to c:\tomcat5\webapps. Start the tomcat server. Now

struts-blank folder is created .

Copy that struts-blank folder and paste it in desktop. Rename the folder as kala..

Now, place that folder(kala) in c:\tomcat5\webapps.( Assuming that we have

installed tomcat5 in C drive). Here kala folder is ourcontext. Restart the tomcat

server.. Open the Browser, type the URL as http://localhost:8080/kala. Now the

welcome page will appear. This means that our installation process is correct.

We require weblogic7 and JDK1.4.2 for developing this exercise

/---------------------------------------------------------------------------------------------------

--------

The following lesson illustrates the method of connecting to a stateless session

bean in weblogic7 server through a Struts-based program.

We have installed weblogic7 and JDK1.4.2 in D:\drive . Create a folder

strutsejbdemo in D drive. This is our working directory.

We have already created the context kala in tomcat5 as mentioned above. .

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Copy that kala context folder to D:\bea\user_projects\mydomain\applications

In this lesson, we have created two packages namely demo and demo1. For this we

have created the two folders namely demo and demo1 in

:D\bea\user_projects\mydomain\applications\kala\web-inf\classes\ to copy theclass files

D:\>cd strutsejbdemo

D:\strutsejbdemo>

When we use struts the concept of package is very important.

D:\strutsejbdemo>md demo1

Here demo1 is our package

D:\strutsejbdemo>cd demo1

Next we create a batch file to set path and classpath

D:\strutsejbdemo\demo1>edit setpath.bat

set path=c:\windows\system32;d:\jdk1.4.2\bin;d:\bea\weblogic700\server\bin

( I am using WindowsXP. If you are using Windows-2000, the path to edit

program should be :c:\winnt\system32.)

Usually we give a class path to working directory. When we use package we

giveclasspath to parent directory. This is very important.

D:\strutsejbdemo\demo1\edit setcpath.bat

set classpath=d:\strutsejbdemo\demo1;d:\strutsejbdemo;

d:\bea\weblogic700\server\lib\weblogic.jar

After creating batch files in the working folder,

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Give the following command:

d:\strutsejbdemo\demo1>setpath

This will set the path for the window

d:\strutsejbdemo\demo1>setcpath

( This will set the classpath for the window ).

Checkup as follows:

D:\strutsejbdemo\demo1>path

D:\strutsejbdemo\demo1>echo %classpath%

Now edit the following files

1.cityguide.java

2.ciyRemote.java

3.cityHome.java

4.cityBean.java

D:\strutsejbdemo\demo1>edit cityguide.java

package demo1;

import java.util.*;

public class cityguide

{

public String listcities(String a)

{

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Vector vector1=new Vector();

if(a.equals("TAMILNADU"))

{

vector1.addElement("Madras");

vector1.addElement("Trichy");

vector1.addElement("Madurai");

}

if(a.equals("KERALA"))

{

vector1.addElement("Cochin");

vector1.addElement("Quicon");

vector1.addElement("Trivandrum");

}

if(a.equals("KARNATAKA"))

{

vector1.addElement("Mysore");

vector1.addElement("Bangalore");

vector1.addElement("Hubli");

}

String r="";

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int n=vector1.size();

for(int j=0;jedit cityRemote.java

package demo1;

import javax.ejb.*;

import java.rmi.*;

public interface cityRemote extends EJBObject

{

public String showcities(String s)

throws RemoteException;

}

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//--------------------------------------------------------------------------------------------------

--------

D:/strutsejbdemo/demo1>edit cityHome.java

package demo1;

import javax.ejb.*;

import java.rmi.*;

public interface cityHome extends EJBHome

{

public cityRemote create()

throws CreateException, RemoteException;

}

//---------------------------------------------------------------------------------

D:/strutsejbdemo/demo1>edit cityBean.java

package demo1;

import javax.ejb.*;

public class cityBean implements SessionBean

{

public String showcities(String s)

{

cityguide guide1= new cityguide();

String r = guide1.listcities(s);

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return r;

}

public void ejbCreate() {}

public void ejbRemove() {}

public void ejbActivate() {}

public void ejbPassivate() {}

public void setSessionContext(SessionContext sc) {}

}

//--------------------------------------------------------------------------------------------------

--------

We have already set the specified path and classpath. Compile all the above files

D:\strutsejbdemo\demo1>javac *.java

D:\ejbstrutsdemo\demo1>copy *.class

d:\bea\user_projects\mydomain\applications\kala\web-inf\classes\demo1

D:\strutsejbdemo>demo1\cd..

D:\strutsejbdemo>md META-INF

When we use package META-INF folder is created in parent folder. It should be

in uppercase ie.,META-INF not meta-inf

Now edit the ejb-jar.xml and weblogic-jar.xml in META-INF

D:\strutsejbdemo\META-INF>edit ejb-jar.xml

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city

demo1.cityHome

demo1.cityRemote

demo1.cityBean

Stateless

Container

//--------------------------------------------------------------------------------------------------

D:\strutsejbdemo\META-INF >edit weblogic-jar.xml

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"http://www.bea.com/servers/wls700/dtd/weblogic-ejb-jar.dtd">

city

cityJndi

//----------------------------------------------------------------------------------

Now, cd back to D:\strutsejbdemo\

Create the jar file as follows:

D:\strutsejbdemo\>jar cf city.jar demo1\*.class META-INF\*.xml

Carefully note that the jar file is created in parent directory.

Now we check up the jar file as follows

D:\strutsejbdemo>java weblogic.ejbc city.jar city1.jar

If there are no problems , we get the ejbc successful message

Now, we copy the jar file to the WebLogic folder as shown below.

D:\strutsejbdemo>copy city1.jar d:\bea\user_projects\mydomain\applications

Start the weblogic server as start->programfiles->BEA weblogic->user_projects-

>mydomain->start server

The city1.jar will be deployed by the server. The development of the EJB and its

deployment in WebLogic server is over.

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//--------------------------------------------------------------------------------------------------

--------Now we develop the Struts client program for the above EJB.

D:\ejbstrutsdemo>md demo

D:\ejbstrutsdemo>demo

D:\strutsejbdemo\demo>edit setcpath.bat

set classpath=%classpath%;d:\strutsejbdemo;e:\struts1.1\lib\struts.jar;

D:\strutsejbdemo\demo>setcpath

We use the following six files, in this demo package,

1. kalaSubmit.jsp

2. kalaForm.java(derived from ActionForm)

3. kalaAction.java(derived from Action)

4. kalahelper.java ( a utility bean)

5. kalaresult.java ( a value bean)

6. kalaOutput.jsp

( besides the web.xml ,struts-config.xml files & application.properties file)

D:\ejbstrutsdemo\demo1>edit kalaSubmit.jsp

STRUTS CLIENT FOR STATELESS

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State

Whick State Do you want to tour?

TAMILNADU?KERALA?KANADA?

//--------------------------------------------------------------------------------------------------

--------

When the user submits the kalaSubmit.jsp, the formbean is automatically filled up

with the values from the jsp-page and the flow goes to the ActionServlet.

tag is used to displaying error messages.

D:\strutsejbdemo\demo>edit kalaForm.java

package demo;

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import javax.servlet.http.*;

import org.apache.struts.action.*;

public class kalaForm extends ActionForm

{

String state =null;

public String getState()

{

return state;

}

public void setState(String a)

{

state=a;

}

public void reset(ActionMapping mapping,

HttpServletRequest request)

{

state=null;

}

public ActionErrors validate (ActionMapping mapping, HttpServletRequest

request)

{

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ActionErrors errors = new ActionErrors();

if( state.length()= =0)

{

errors.add("state", new ActionError("errors.nullstate"));

}

return errors;

}

}

//--------------------------------------------------------------------------------------------------

--------

D:\strutsejbdemo\demo>edit kalahelper.java

package demo;

import java.util.*;

import javax.ejb.*;

import javax.rmi.*;

import javax.naming.*;

import java.rmi.*;

import java.io.*;

public class kalahelper

{

public String callejb(String s)

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{

String r;

try

{

System.out.println("Please Wait...");

Properties props=new Properties();

props.put(Context.INITIAL_CONTEXT_FACTORY,

"weblogic.jndi.WLInitialContextFactory");

String url="t3://127.0.0.1:7001";

props.put(Context.PROVIDER_URL,url);

Context context=new InitialContext(props);

System.out.println("ConnectionOK");

demo1.cityHome home=

(demo1.cityHome)context.lookup("cityJndi");

System.out.println("HOME LOCATED");

demo1.cityRemote remote= home.create();

System.out.println("REMOTE READY");

r=remote.showcities(s);

}

catch(Exception e1){ r=""+e1; }

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return r;

}

}

//-------------------------------------------------------------------------------------------------

D:\strutsejbdemo\demo>edit kalaresult.java

package demo;

public class kalaresult

{

String value;

public kalaresult()

{

value=" ";

}

public String getValue(){

return value;

}

public void setValue(String v){

value=v;

}

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}

//--------------------------------------------------------------------------------------------------

--

The Action Class is part of the Model and is a wrapper around the business logic.

The purpose of Action Class is to translate the HttpServletRequest to the business

logic

In our case, the action class instance is using a helper to perform the business logic.

This is the bettter and recommended practice.

D:\strutsejbdemo\demo>edit kalaAction.java

package demo;

import java.io.*;

import java.util.*;

import javax.servlet.*;

import javax.servlet.http.*;

import org.apache.struts.action.*;

public class kalaAction extends Action

{

public ActionForward execute(ActionMapping mapping,

ActionForm form,

HttpServletRequest request,

HttpServletResponse response)

throws IOException, ServletException

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{

kalaForm kalaform =(kalaForm) form;

String a = kalaform.getState();

if(a.equals("TAMILNADU") || a.equals("KERALA") ||

a.equals("KARNATAKA"))

{

kalahelper helper = new kalahelper();

String r = helper.callejb(a);

kalaresult kr = new kalaresult();

kr.setValue(r);

String m = kr.getValue();

System.out.println(m);

HttpSession session= request.getSession();

session.setAttribute("result",kr);

return (mapping.findForward("success"));

}

else

{

ActionErrors errors = new ActionErrors();

errors.add (ActionErrors.GLOBAL_ERROR, new

ActionError("errors.wrongname"));

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saveErrors(request,errors);

return(mapping.findForward("failure"));

}

}

}

D:\strutsejbdemo\demo>edit kalaOutput.jsp

Now we are ready to compile the above programs.class path are already specified

D:\strutsejbdemo\demo>javac *.java

D:\strutsejbdemo\demo>copy *.jsp

d:\bea\user_projects\mydomain\applications\kala

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D:\strutsejbdemo\demo>copy *.class

d:\bea\user_projects\mydomain\applications\kala\web-inf\classes\demo

The deployment process is over

Go to another window. cd to

D:\bea\user_projects\mydomain\applications\kala\web-inf>edit struts-config.xml

In the struts-config.xml file, we make two entries. One entry is for the instance

ofkalaForm and the other entry is for the instance ofkalaAction class.

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

( this is the part dealing with the formbean)

The next segment of mapping in

struts-config.xml deals with the action mapping for QueryAction.

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. There is a file known as 'Application.properties' in 'WEB-INF\classes\resources'

and at the end of that file we will add the following lines.

errors.nullstate= ENTER YOUR STATE

errors.wrongname=SORRY.., SERVICE NOT PROVIDED FOR

THIS STATE

Therefore, we will get the specified error messages.

Start the weblogic server as usual.

Open the browser and type URL as http://localhost:7001/kala/kalaSubmit.jsp

Type the name of the state ( TAMILNADU/KERALA/KARNATAKA)in the

text box & then click submit. If the name of the state is correct then result will be

displayed. Otherwise the home page remains with the values entered and also with

the error message. As the main purpose of this note is just to explain how to

connect to stateless ejb using Struts, I am leaving out Validation Framework

details.