htdocs.hello-world.html Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of openejb-webadmin Show documentation
The newest version!





Hello World! --              A basic EJB example 
OpenEJB at SourceForge     OpenEJB at Exolab     
 

Main
   Welcome!
   Download
   Mailing Lists
   The Team
Users
   Quickstart
   Hello World!
   Deploy
   Startup
   Support
   Request Feature
Servers
   Local Server
   Remote Server
Adapters
   Tomcat
Integrators
   Why OpenEJB
   Overview
   Design
   Specification
   Presentation
Developers
   Release Plan
   Source Code
   SourceForge


    


Hello World!
A basic EJB example

Before starting       This example assumes you have already downloaded and installed OpenEJB in the  directory c:\openejb. Refer to the QuickStart Guide if you  haven't yet installed OpenEJB. 
 We also assume that you are running your client from the directory c:\my\app.
  Create the bean class  First, create the package where we will place our ejb and application files. 
  c:\my\app> mkdir org
 c:\my\app> mkdir org\acme   In your favorite editor, create the file below. 
  
c:\my\app\org\acme\HelloBean.java
package org.acme;

import java.rmi.RemoteException;
import javax.ejb.*;

public class HelloBean implements SessionBean {
  private SessionContext sessionContext;
  public void ejbCreate() {
  }
  public void ejbRemove() {
  }
  public void ejbActivate() {
  }
  public void ejbPassivate() {
  }
  public void setSessionContext(SessionContext sessionContext) {
    this.sessionContext = sessionContext;
  }
  public String sayHello() throws java.rmi.RemoteException {
    return "Hello World!!!!!";
  }
}
 
  Create the EJB Home interface  
c:\my\app\org\acme\HelloHome.java
package org.acme;

import java.rmi.*;
import javax.ejb.*;
import java.util.*;

public interface HelloHome extends EJBHome {
  public HelloObject create() throws RemoteException, CreateException;
}
 
  Create the EJB Object interface  
c:\my\app\org\acme\HelloObject.java
package org.acme;

import java.rmi.*;
import javax.ejb.*;
import java.util.*;

public interface HelloObject extends EJBObject {
  public String sayHello() throws RemoteException;
}
 
  Create the ejb-jar.xml  c:\my\app> mkdir META-INF 
  
c:\my\app\META-INF\ejb-jar.xml
<?xml version="1.0" encoding="UTF-8"?>
<ejb-jar>
  <enterprise-beans>
    <session>
      <ejb-name>Hello</ejb-name>
      <home>org.acme.HelloHome</home>
      <remote>org.acme.HelloObject</remote>
      <ejb-class>org.acme.HelloBean</ejb-class>
      <session-type>Stateless</session-type>
      <transaction-type>Container</transaction-type>
    </session>
  </enterprise-beans>
  <assembly-descriptor>
    <container-transaction>
      <method>
        <ejb-name>Hello</ejb-name>
        <method-name>*</method-name>
      </method>
      <trans-attribute>Required</trans-attribute>
    </container-transaction>
  </assembly-descriptor>
</ejb-jar>
 
  Compile the EJB  C:\my\app> javac org\acme\*.java 
   
 NOTE
 To compile an EJB, you need to have Sun's EJB library in your classpath.  One has been included for you in the directory lib/ejb-2.0.jar 
 
   Package the EJB  C:\my\app> jar cvf myHelloEjb.jar org META-INF 
  Deploy the EJB jar  Use the OpenEJB Deploy Tool to deploy your jar. 
    C:\my\app> cd C:\openejb
 C:\openejb> openejb.bat deploy -a -m c:\my\app\myHelloEjb.jar 
   A basic client application   Create a basic client application to access your HelloWorld bean. 
    
c:\my\app\org\acme\HelloWorld.java
package org.acme;

import javax.rmi.*;
import javax.naming.*;
import java.util.*;

public class HelloWorld {

 public static void main( String args[]) {
  try{
    
    Properties p = new Properties();
    
    //The JNDI properties you set depend
    //on which server you are using.
    p.put("java.naming.factory.initial", ... 
    ...
    
    //Now use those properties to create
    //a JNDI InitialContext with the server.
    InitialContext ctx = new InitialContext( p );
    
    //Lookup the bean using it's deployment id
    Object obj = ctx.lookup("/Hello");
    
    //Be good and use RMI remote object narrowing
    //as required by the EJB specification.
    HelloHome ejbHome = (HelloHome)
        PortableRemoteObject.narrow(obj,HelloHome.class);

    //Use the HelloHome to create a HelloObject
    HelloObject ejbObject = ejbHome.create();
    
    //The part we've all been wainting for...
    String message = ejbObject.sayHello();

    //A drum roll please.
    System.out.println( message );
    
  } catch (Exception e){
    e.printStackTrace();
  }
 }
}

 
    JNDI properties for the Local Server would look like the following.  Be sure to read the Local Server documentation if you run into any problems. 
    
Properties p = new Properties();

p.put("java.naming.factory.initial", 
    "org.openejb.core.ivm.naming.InitContextFactory");
p.put("openejb.home", "c:\\openejb");
    
InitialContext ctx = new InitialContext(p);
 
   JNDI properties for the Remote Server would look like the following.  Be sure to start the Remote Server before running your application.  See the Remote Server  documentation for more information on  using the Remote Server. 
    
Properties p = new Properties();
p.put("java.naming.factory.initial", 
    "org.openejb.client.JNDIContext");
p.put("java.naming.provider.url", "127.0.0.1:4201");
p.put("java.naming.security.principal", "myuser");
p.put("java.naming.security.credentials", "mypass");
    
InitialContext ctx = new InitialContext(p);
 
   Update the HelloWorld.java to contain the right JNDI properties. 
   Compile the application  C:\my\app> javac org\acme\HelloWorld.java 
   
 NOTE
 To compile this application, you need to have Sun's  JNDI library in your classpath.  One has been included for you in the directory lib/jndi_1.2.1.jar 
 
   Run it!  When you run OpenEJB in embedded server mode, you need all the server libraries in your classpath along with your beans and client code.  Here is a simple script  that will add those classes automactically.  Feel free to use this script, or add it's contents to you own scripts. 
   c:\my\app\RunIt.bat
@echo off

set OPENEJB_HOME=C:\openejb
set PATH=%PATH%;%OPENEJB_HOME%\bin
set JAVA=%JAVA_HOME%\bin\java

set CP=
for %%i in (%OPENEJB_HOME%\lib\*.jar) do call cp.bat %%i 
for %%i in (%OPENEJB_HOME%\dist\*.jar) do call cp.bat %%i 
for %%i in (%OPENEJB_HOME%\beans\*.jar) do call cp.bat %%i 
set CLASSPATH=%JAVA_HOME%\lib\tools.jar;%CP%

%JAVA% %OPTIONS% -Dopenejb.home=%OPENEJB_HOME% org.acme.HelloWorld
  Now run the script! 
   C:\my\app> RunIt 
   What if it didn't work  If you ran into any problems, first check your openejb.log file at c:\openejb\openejb.log. Look for any lines that begin with "WARN", "ERROR", or  "FATAL". 
   If the log file doesn't help you, email it to the OpenEJB  user mailing list and let people know you are using the Hello World example. 
   
         
     
     
  


     Java, EJB, JDBC, JNDI, JTA, Sun, Sun Microsystems are trademarks or registered     trademarks of Sun Microsystems, Inc. in the United States and in other     countries. XML, XML Schema, XSLT and related standards are trademarks or registered     trademarks of MIT, INRIA, Keio or others, and a product of the World Wide Web     Consortium. All other product names mentioned herein are trademarks of their respective     owners.