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.
The classes and interfaces
Create the package where we will place our ejb and application files, let's say "c:\my\app" for our example.
Windows
c:\my\app> mkdir org
c:\my\app> mkdir org\acme
Linux/Unix
user@host app# mkdir org
user@host app# mkdir org/acme
Create the files below in our new "c:\my\app\org\acme\" directory
Create the bean class
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
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
package org.acme;
import java.rmi.*;
import javax.ejb.*;
import java.util.*;
public interface HelloObject extends EJBObject {
public String sayHello() throws RemoteException;
}
The deployment descriptor
The deployment descriptor tells the EJB Container how to put together the classes above and run your component.
Fisrt, create a "META-INF" directory in the "c:\my\app" directory.
Windows
c:\my\app> mkdir META-INF
Linux/Unix
user@host app# mkdir META-INF
Now, create an ejb-jar.xml file in your META-INF directory.
<?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
Compile your bean.
Windows
c:\my\app> javac org\acme*.java
Linux/Unix
user@host app# javac org/acme/*.java
Make sure you don't make the mistake of trying to compile your classes while sitting inside the org/acme/ directory.
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-1.0.jar
Package the EJB
Now, package your EJB classes and your META-INF directory into a jar.
Windows
C:\my\app> jar cvf myHelloEjb.jar org META-INF
Linux/Unix
user@host app# jar cvf myHelloEjb.jar org META-INF
That command should give you output like the following.
added manifest adding: org/(in = 0) (out= 0)(stored 0%) adding: org/acme/(in = 0) (out= 0)(stored 0%) adding: org/acme/HelloBean.class(in = 946) (out= 467)(deflated 50%) adding: org/acme/HelloObject.class(in = 234) (out= 177)(deflated 24%) adding: org/acme/HelloHome.class(in = 263) (out= 188)(deflated 28%) ignoring entry META-INF/ ignoring entry META-INF/MANIFEST.MF adding: META-INF/ejb-jar.xml(in = 733) (out= 319)(deflated 56%)
Check to make sure at least the three classes are there and the ejb-jar.xml is there and that everything is in the directories you see above.
Deploy the EJB jar
Use the OpenEJB Deploy Tool to deploy your jar.
Windows
C:\my\app> cd C:\openejb
C:\openejb> openejb.bat deploy -a -m c:\my\app\myHelloEjb.jar
Linux/Unix
user@host app# cd /openejb
user@host openejb# ./openejb.sh deploy -a -m /my/app/myHelloEjb.jar
Since the OpenEJB deployment tool writes to your jar file, make sure that no other programs are using it when you deploy (i.e. if you use an editor such as Forte for Java to create the jar file, that editor may still be using it). If you get an error such as "Error in writing existing jar file" close any programs that may be using the jar and try deploying again.
A basic client application
Create a basic client application to access your HelloWorld bean.
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();p.put("java.naming.factory.initial", "org.openejb.client.RemoteInitialContextFactory");
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 );
Object obj = ctx.lookup("/Hello");
HelloHome ejbHome = (HelloHome)
PortableRemoteObject.narrow(obj,HelloHome.class);
HelloObject ejbObject = ejbHome.create();
String message = ejbObject.sayHello();
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.client.LocalInitialContextFactory");
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.RemoteInitialContextFactory");
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
Compile your client code. Don't forget to add your EJBs in the classpath!
Windows
C:\my\app> javac org\acme\HelloWorld.java
Linux/Unix
user@host app# javac org/acme/HelloWorld.java
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.
Example Windows Batch script.
@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
Example Linux/Unix Batch script.
#!/bin/sh
# Set OPENEJB_HOME to the full path where you
# installed your OpenEJB distribution
export OPENEJB_HOME=/openejb
# Set JAVA_HOME to the full path where you
# installed your JDK distribution
export JAVA_HOME=/usr/java/jdk1.3.1
export PATH=${PATH}:${OPENEJB_HOME}/bin
export JAVA=${JAVA_HOME}/bin/java
export CP=
CP=`echo $OPENEJB_HOME/lib/*.jar | tr ' ' ':'`:${CP}
CP=`echo $OPENEJB_HOME/dist/*.jar | tr ' ' ':'`:${CP}
CP=`echo $OPENEJB_HOME/beans/*.jar | tr ' ' ':'`:${CP}
export CLASSPATH=$JAVA_HOME/lib/tools.jar:${CP}
$JAVA -Dopenejb.home=$OPENEJB_HOME org.acme.HelloWorld
Now run the script!
Windows
C:\my\app> RunIt
Linux/Unix
user@host app# ./RunIt.sh
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 ** , ** , or ** .
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.