. Java Stateless Session EJB

Java Stateless Session EJB

A Stateless Session EJB

Note: This Example Uses J2EE 1.3

The Remote Interface - RockPaperScissors.java

import javax.ejb.EJBObject;	
import java.rmi.RemoteException;	
	
public interface RockPaperScissors extends EJBObject 
{	 	
   public String getRockPaperOrScissors() 
     throws RemoteException;	
}

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The Home Interface - RockPaperScissorsHome.java

import java.rmi.RemoteException;	
import javax.ejb.CreateException;	
import javax.ejb.EJBHome;	
	
public interface RockPaperScissorsHome extends EJBHome 
{	
   RockPaperScissors create() throws RemoteException, 
                                     CreateException;	
}

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The Enterprise Bean Class - RockPaperScissorsBean.java

import java.util.Random;
import javax.ejb.SessionBean;	
import javax.ejb.SessionContext;	
	
public class RockPaperScissorsBean implements SessionBean {	
 	
   Random random;   
   //All methods in the Remote interface must be implemented here:	
   public String getRockPaperOrScissors() {	
      if (random == null) {random = new Random();}
      int randomInt = random.nextInt(3);
      if (randomInt == 0) 
        {return "Rock";}
      else if (randomInt == 1) 
        {return "Paper";} 
      else
        {return "Scissors";}        
   }	
	
   public void RockPaperScissorsBean() {}
   
   //the following five methods must be in the Enterprise Bean Class:
   public void ejbCreate() {}	
   //ejbCreate() must match Home Interface's create() method signature
   public void ejbRemove() {}	
   public void ejbActivate() {}	
   public void ejbPassivate() {}	
   public void setSessionContext(SessionContext sessionContext) {}
}

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ejb-jar.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE ejb-jar PUBLIC '-//Sun Microsystems, Inc.//DTD Enterprise JavaBeans 2.0//EN' 'http://java.sun.com/dtd/ejb-jar_2_0.dtd'>
<ejb-jar>
  <display-name>RockPaperScissorsJAR</display-name>
  <enterprise-beans>
    <session>
      <display-name>RockPaperScissorsEJB</display-name>
      <ejb-name>RockPaperScissorsEJB</ejb-name>
      <home>RockPaperScissorsHome</home>
      <remote>RockPaperScissors</remote>
      <ejb-class>RockPaperScissorsBean</ejb-class>
      <session-type>Stateless</session-type>
      <transaction-type>Bean</transaction-type>
  </enterprise-beans>
</ejb-jar>

A Client Application - RockPaperScissorsClient.java

import javax.naming.Context;	
import javax.naming.InitialContext;	
import javax.rmi.PortableRemoteObject;		
	
public class RockPaperScissorsClient {	
	
   public static void main(String[] args) {	
      try {     
          
          Context initialContext = new InitialContext();
          Object initialContextObject = 
            initialContext.lookup(
              "java:comp/env/ejb/SimpleRockPaperScissors");
	  RockPaperScissorsHome rockPaperScissorsHome = 	
             (RockPaperScissorsHome)PortableRemoteObject.narrow(
               initialContextObject, RockPaperScissorsHome.class);
          RockPaperScissors rockPaperScissors = 
            rockPaperScissorsHome.create();
          String theBeansRPS = 
            rockPaperScissors.getRockPaperOrScissors();
          String theApplicationsRPS = "Scissors"; 
            //the application always picks "Scissors";
      
          if (theBeansRPS.equals("Rock") && 
              theApplicationsRPS.equals("Rock")) {
                System.out.println("Tie!");
          } else if (theBeansRPS.equals("Rock") && 
                     theApplicationsRPS.equals("Paper")) {
              System.out.println("The Application wins!");
          } else if (theBeansRPS.equals("Rock") && 
                     theApplicationsRPS.equals("Scissors")) {
              System.out.println("The Bean wins!");
          } else if (theBeansRPS.equals("Paper") && 
                     theApplicationsRPS.equals("Rock")) {
              System.out.println("The Bean wins!");
          } else if (theBeansRPS.equals("Paper") && 
                     theApplicationsRPS.equals("Paper")) {
              System.out.println("Tie!");
          } else if (theBeansRPS.equals("Paper") && 
                     theApplicationsRPS.equals("Scissors")) {
              System.out.println("The Application wins!");
          } else if (theBeansRPS.equals("Scissors") && 
                     theApplicationsRPS.equals("Rock")) {
              System.out.println("The Application wins!");
          } else if (theBeansRPS.equals("Scissors") && 
                     theApplicationsRPS.equals("Paper")) {
              System.out.println("The Bean wins!");
          } else if (theBeansRPS.equals("Scissors") && 
                     theApplicationsRPS.equals("Scissors")) {
              System.out.println("Tie!");
          } else  {System.out.println("Someone didn't choose!");}
          
          System.out.println("The Bean chose " + theBeansRPS + 
                             ", while the Application chose " + 
                             theApplicationsRPS + ".");                
                  
          rockPaperScissors.remove();	//clean up
      
       } catch (Exception exception) {	
          System.err.println("Exception!");	
          exception.printStackTrace();	
       }          
   } 	
}

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application-client.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE application-client PUBLIC '-//Sun Microsystems, Inc.//DTD J2EE Application Client 1.3//EN' 'http://java.sun.com/dtd/application-client_1_3.dtd'>
<application-client>
  <display-name>RockPaperScissorsClient</display-name>
  <ejb-ref>
    <ejb-ref-name>ejb/SimpleRockPaperScissors</ejb-ref-name>
    <ejb-ref-type>Session</ejb-ref-type>
    <home>RockPaperScissorsHome</home>
    <remote>RockPaperScissors</remote>
  </ejb-ref>
</application-client>

A Client JSP - RockPaperScissorsJSP.jsp

                    
<%@ page import="javax.naming.*, javax.rmi.PortableRemoteObject,
RockPaperScissors, RockPaperScissorsHome" %>
<%!
 RockPaperScissors rockPaperScissors = null;

 public void jspInit() { 
    try {
       InitialContext initialContext = 
         new InitialContext();
       Object initialContextObject = 
         initialContext.lookup("java:comp/env/ejb/TheRockPaperScissors");
       RockPaperScissorsHome rockPaperScissorsHome = 
         (RockPaperScissorsHome)PortableRemoteObject.narrow(
           initialContextObject, RockPaperScissorsHome.class);
       rockPaperScissors = rockPaperScissorsHome.create();
    } catch (java.rmi.RemoteException remoteException) {
          System.out.println(
            "RemoteException - Couldn't create RockPaperScissors bean." +
              remoteException.getMessage());
    } catch (javax.ejb.CreateException createException) {
          System.out.println(
            "CreateException - Couldn't create RockPaperScissors bean." +
              createException.getMessage());
    } catch (NamingException namingException) {
          System.out.println(
            "Unable to lookup home TheRockPaperScissors " +
              namingException.getMessage());
    } 
 }
%>
<html>
<head><title>Rock-Paper-Scissors</title></head>
<body>
<h3>Choose Rock, Paper, or Scissors</p>	
<form method="get">	
ROCK <input type="radio" name="rps" value="Rock" checked><br>
PAPER<input type="radio" name="rps" value="Paper"><br>	
SCISSORS<input type="radio" name="rps" value="Scissors"><br>
<input type="submit" value="Submit">	
<input type="reset" value="Reset">	
</form>	

<%	
   String theJspRPS = request.getParameter("rps");	
   String theBeansRPS = rockPaperScissors.getRockPaperOrScissors();
   
   if (theBeansRPS == null) {theBeansRPS = "no pick from the Bean";}

   String whoWins;
   if (theJspRPS == null) {whoWins=" ";} //first time no jsp pick
   else
   {
        if (theBeansRPS.equals("Rock")     && 
            theJspRPS.equals("Rock"))     {
              whoWins="Tie!";
        } else if (theBeansRPS.equals("Rock")     && 
                   theJspRPS.equals("Paper"))    {
              whoWins="You win!";
        } else if (theBeansRPS.equals("Rock")     && 
                   theJspRPS.equals("Scissors")) {
              whoWins="The Bean wins!";
        } else if (theBeansRPS.equals("Paper")    && 
                   theJspRPS.equals("Rock"))     {
              whoWins="The Bean wins!";
        } else if (theBeansRPS.equals("Paper")    && 
                   theJspRPS.equals("Paper"))    {
              whoWins="Tie!";
        } else if (theBeansRPS.equals("Paper")    && 
                   theJspRPS.equals("Scissors")) {
              whoWins="You win!";
        } else if (theBeansRPS.equals("Scissors") && 
                   theJspRPS.equals("Rock"))     {
              whoWins="You win!";
        } else if (theBeansRPS.equals("Scissors") && 
                   theJspRPS.equals("Paper"))    {
              whoWins="The Bean wins!";
        } else if (theBeansRPS.equals("Scissors") && 
                   theJspRPS.equals("Scissors")) {
              whoWins="Tie!";
        } else {whoWins = "Someone didn't choose!";}
   whoWins = (whoWins + " The Bean chose " +  theBeansRPS + 
                        " while you chose " + theJspRPS + ".");
   }
%>	
<%= whoWins %>  
</body>
</html>

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References

online

J2EE (TM) 1.3 Tutorial from Sun

Books

Enterprise Java Beans by Richard Monson-Haefel
Mastering Enterprise JavaBeans by Ed Roman

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Comment by archive Rate this Comment

In an effort to learn ejbs i scrapped your examples of the html page and created a tgz of them in which each bean type has a different sub-directory.

If you want you can put a link to my sight.
http://www.zingaretti.com/technical_corner/technical_corner.jsp

As i make the consumable by jboss i will updated the tgz file.