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EJB3.0: Call Back Listener not working.

 
Gurumurthy Ramamurthy
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EJB 3.0 Call Back methods are working, but the listeners are not working.

ListenerHelloCallBack.java (Interface)
/**
* This is the ListenerHelloCallBack business interface.
*/

public interface ListenerHelloCallBack {

/**
* @return a greeting to the client.
*/
public String listenerHelloCallBack();
}


Bean class:
import javax.ejb.*;
import javax.ejb.*;

/**
* Demonstration stateless session bean.
*/
@Stateful
@Remote(ListenerHelloCallBack.class)
@CallbackListener(CallBackListener.class)
public class ListenerHelloCallBackBean implements ListenerHelloCallBack {
public String listenerHelloCallBack() {
System.out.println("listenerHelloCallBack()");
return "Hello, Call Back Listener World!";
}
}

Call Back Listener class:

import javax.ejb.*;
import javax.ejb.*;

public class CallBackListener {

@Init
public void sayInit(Object obj)
{
System.out.println("This would be called upon Init from listener class");
}

@PostConstruct
public void sayPostConstruct(Object obj)
{
System.out.println("This would be called upon post construct from listener class");
}


@PreDestroy
public void sayPreDestroy(Object obj)
{
System.out.println("This would be called upon pre destroy from listener class");
}

@PrePassivate
public void sayPrePassivate(Object obj)
{
System.out.println("This would be called upon pre passivate from listener class");
}

@PostActivate
public void sayPostActivate(Object obj)
{
System.out.println("This would be called upon post activate from listener class");
}

public void finalize()
{
System.out.println("Finalize method is getting called...");
}
}


Client:

import javax.naming.Context;
import javax.naming.InitialContext;
import java.util.*;
import javax.naming.*;


/**
* This class is an example of client code which invokes
* methods on a simple, remote stateless session bean.
*/
public class ListenerHelloCallBackClient {

public static void main(String[] args) throws Exception {
/*
* Obtain the JNDI initial context.
*
* The initial context is a starting point for
* connecting to a JNDI tree. We choose our JNDI
* driver, the network location of the server, etc
* by passing in the environment properties.
*/

Properties p = new Properties();

//The JNDI properties you set depend
//on which server you are using.
//These properties are for the Remote Server.
p.put("java.naming.factory.initial", "org.jnp.interfaces.NamingContextFactory");
p.put("java.naming.provider.url", "jnp://localhost:1099");
p.put("java.naming.factory.url.pkgs", "org.jboss.naming rg.jnp.interfaces");

Context ctx = new InitialContext(p);


/*
* Get a reference to a bean instance, looked up by class name
*/
ListenerHelloCallBack listenerHelloCallBack = (ListenerHelloCallBack) ctx.lookup("ListenerHelloCallBack");


/*
* Call the helloCallBack() method on the bean.
* We then print the result to the screen.
*/
System.out.println(listenerHelloCallBack.listenerHelloCallBack());
listenerHelloCallBack=null;

}
}


But, none of the call back methods like @init, @postconstruct are working.

Please help.

Thanks,
Guru
 
Shailesh Kini
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Hi,

I believe you can use Interceptors with Stateful Session beans for the callback methods.

Instead of @CallbackListener(CallbackListener.class)

use @Interceptors({CallbackListener.class}) in your Stateful EJB implementation class. You should find Interceptor annotation class in javax.interceptor.InvocationContext package.

You can leave all the other methods in CallbackListener class as they should be called appropriately.

Best Regards,
Shailesh Kini
 
Gurumurthy Ramamurthy
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Thanks Shailesh.

Yes, it is working now after doing @Interceptor.

But, why we should not use @CallbackListener? Can we use it for atleast stateless session beans?

Thanks,
Guru
 
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