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RMI callback with JBoss

I'm trying to call an EJB method on a JBoss server, passing it a reference to the client object so that I can receive a

callback. I used to have this working when we were using Weblogic, but I can't seem to get it to work for JBoss.

The EJB's interface includes a nested interface that extends Remote:

public interface TestEjb extends EJBObject {
public void register(Callback callback) throws RemoteException;

public interface Callback extends Remote {
public void send(String message) throws RemoteException;
}
}

My client implements that interface:

public class TestClient extends UnicastRemoteObject implements TestEjb.Callback {
...
public void send(String message) {
System.out.println("Message from server: '" + message + "'");
}
...
}

I expect to be able to pass "this" to TestEbj.register. However, I get an IllegalArgumentException from the server, claiming

that I am passing the wrong number of arguments.

Steps to reproduce:

1) Get the source files here: http://www.everybody.org/~jeremystein/code/CallbackTest.zip
2) Extract the zip file
3) The server directory contains the Test EJB. Deploy it on a JBoss server.
4) The EjbInterface.jar file contains these classes needed to compile the client.
- TestEjb$Callback.class
- TestEjb.class
- TestEjbHome.class
(You could create this jar yourself after compiling the EJB classes.)
5) Grab jbossall-client.jar from the jboss distribution (in the client directory). Put it in the client directory.
6) CD to the client directory.
7) javac -d . -classpath EjbInterface.jar;jbossall-client.jar TestClient.java
8) rmic -classpath .;EjbInterface.jar;jbossall-client.jar com.elementk.client.TestClient
9) java -classpath .;EjbInterface.jar;jbossall-client.jar com.elementk.client.TestClient

Detailed exception:

java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
java.rmi.ServerException: RuntimeException; nested exception is:
java.lang.IllegalArgumentException: wrong number of arguments
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:292)
at sun.rmi.transport.Transport$1.run(Transport.java:148)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:144)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:460)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:701)
at java.lang.Thread.run(Thread.java:534)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknown Source)
at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
at sun.rmi.server.UnicastRef.invoke(Unknown Source)
at org.jboss.invocation.jrmp.server.JRMPInvoker_Stub.invoke(Unknown Source)
at org.jboss.invocation.jrmp.interfaces.JRMPInvokerProxy.invoke(JRMPInvokerProxy.java:135)
at org.jboss.invocation.InvokerInterceptor.invoke(InvokerInterceptor.java:96)
at org.jboss.proxy.TransactionInterceptor.invoke(TransactionInterceptor.java:46)
at org.jboss.proxy.SecurityInterceptor.invoke(SecurityInterceptor.java:45)
at org.jboss.proxy.ejb.StatelessSessionInterceptor.invoke(StatelessSessionInterceptor.java:100)
at org.jboss.proxy.ClientContainer.invoke(ClientContainer.java:85)
at $Proxy2.register(Unknown Source)
at com.elementk.client.TestClient.main(TestClient.java:25)
Caused by: java.rmi.ServerException: RuntimeException; nested exception is:
java.lang.IllegalArgumentException: wrong number of arguments
at org.jboss.ejb.plugins.LogInterceptor.handleException(LogInterceptor.java:361)
at org.jboss.ejb.plugins.LogInterceptor.invoke(LogInterceptor.java:195)
at org.jboss.ejb.plugins.ProxyFactoryFinderInterceptor.invoke(ProxyFactoryFinderInterceptor.java:122)
at org.jboss.ejb.StatelessSessionContainer.internalInvoke(StatelessSessionContainer.java:331)
at org.jboss.ejb.Container.invoke(Container.java:700)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.jboss.mx.capability.ReflectedMBeanDispatcher.invoke(ReflectedMBeanDispatcher.java:284)
at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:546)
at org.jboss.invocation.jrmp.server.JRMPInvoker.invoke(JRMPInvoker.java:367)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:261)
at sun.rmi.transport.Transport$1.run(Transport.java:148)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:144)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:460)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:701)
at java.lang.Thread.run(Thread.java:534)Caused by: java.lang.IllegalArgumentException: wrong number of arguments
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.jboss.ejb.StatelessSessionContainer$ContainerInterceptor.invoke(StatelessSessionContainer.java:683)
at org.jboss.resource.connectionmanager.CachedConnectionInterceptor.invoke(CachedConnectionInterceptor.java:185)
at org.jboss.ejb.plugins.StatelessSessionInstanceInterceptor.invoke(StatelessSessionInstanceInterceptor.java:72)
at org.jboss.ejb.plugins.AbstractTxInterceptor.invokeNext(AbstractTxInterceptor.java:84)
at org.jboss.ejb.plugins.TxInterceptorCMT.runWithTransactions(TxInterceptorCMT.java:267)
at org.jboss.ejb.plugins.TxInterceptorCMT.invoke(TxInterceptorCMT.java:128)
at org.jboss.ejb.plugins.SecurityInterceptor.invoke(SecurityInterceptor.java:118)
at org.jboss.ejb.plugins.LogInterceptor.invoke(LogInterceptor.java:191)
... 21 more

If no one can tell me what's wrong with my code, perhaps someone can point me to a COMPLETE example of RMI callback that works with JBoss.

Mayank S

It says:

>> java.lang.IllegalArgumentException: wrong number of arguments

Perhaps some method is receiving the wrong number of arguments.

JeremyGStein

ASKER

mayankeagle, no doubt that's true. I wish there was a way to turn on logging in the sun.rmi.server.UnicastServerRef class to see what arguments it was using with my method. The client is calling testEjb.register(this). I suspect that RMI is somehow unable to pass the remote object and so it leaves it off the argument list? I don't know how to tell what's really happening.

Mayank S

Does your class implement Serializable?

JeremyGStein

ASKER

mayankeagle,
No, as you can see above, it implements TestEjb.Callback, which means it implements Remote.

Mayank S

Oh, right. I didn't read the whole of your question properly. How do you obtain a reference to the EJB (where you call the method)? Can you show that part of your code?

JeremyGStein

ASKER

OK, here's the whole client. It's also available from the zip file here: http://www.everybody.org/~jeremystein/code/CallbackTest.zip

TestClient.java:
package com.elementk.client;

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

import com.elementk.server.*;

public class TestClient extends UnicastRemoteObject implements TestEjb.Callback {
private static String EJB_NAME = "com.elementk.server.TestEjb";
private static String SERVER_URL = "localhost:1101";

public TestClient() throws RemoteException {
super();
}

public void send(String message) {
System.out.println("Message from server: '" + message + "'");
}

public static void main(String args[]) {
try {
TestClient client = new TestClient();
getEjb().register(client);
} catch (Exception e) {
e.printStackTrace();
System.exit(1);
}
}

private static TestEjb getEjb() throws NamingException, CreateException, RemoteException {
Context context = getContext();
TestEjbHome testEjbHome = (TestEjbHome)context.lookup(EJB_NAME);
return testEjbHome.create();
}

private static Context getContext() throws NamingException {
Properties p = new Properties();
p.put(Context.INITIAL_CONTEXT_FACTORY, "org.jnp.interfaces.NamingContextFactory");
p.put(Context.URL_PKG_PREFIXES, "jboss.naming:org.jnp.interfaces");
p.put(Context.PROVIDER_URL, SERVER_URL);

return new InitialContext(p);
}
}

Mayank S

>> jboss.naming:org.jnp.interfaces

Should this be: org.jboss.naming:org.jnp.interfaces ?

Mayank S

Have a look at this: http://nemesisit.rdsnet.ro/opendocs/simplearch/simplejboss.html

JeremyGStein

ASKER

mayankeagle,

Changing jboss.naming to org.jboss.naming didn't make a difference, although perhaps the latter is more correct.

The link is interesting, but I think it's more geared toward getting through a firewall. I'm not having that problem. The article doesn't mention callbacks or passing remote objects. Thanks.

vzilka

Can you describe here what you want to achieve? Perhaps there is a better way to do it.
Passing this of a remote and expecting the server to understand it needs to get the stub sounds fishy to me.

JeremyGStein

ASKER

vzilka,

There are plenty of reasons for callbacks. When I had this working with Weblogic, I used it for a couple of purposes:
1) The server could decide whether it needed further data and request it as necessary. For large chunks of data that were only sometimes required by the server, this allowed me to pass that data as necessary.
2) Logging. The server would send a message to the callback object with logging information. In my case, I don't have access to the server's production log. By sending logging information back to me, I can diagnose problems more easily.

With RMI, you're supposed to be able to pass either a serializable or a remote object. I can get a serializable object to be passed, but not a remote object. I think the fact that the remote object happens to be "this" shouldn't be important.

vzilka

I am sorry, I did not explain my self correctly.
Of course sending a remote reference from the client is useful.
However, I find it hard to believe it will work. I don't think it is the this usage. I think that the server expects to recieve a stub, and how will this stub be transferred? WHo will create an object of the skeleton to listen to it?
I can think of other solutions, but it depends on your architecture.
Is your client app running in a J2EE container?

JeremyGStein

ASKER

I haven't abandoned the problem. I'm still trying to get this to work.

Mayank S

You should've replied to vzilka.

JeremyGStein

ASKER

vzilka,

I knew that RMI callback is supposed to work, but it took me a long time to find a good example online. Here is such an example:
http://java.sun.com/developer/onlineTraining/rmi/RMI.html#RMIClientSideCallbacks

I believe most of your questions are addressed in the article.

My client is NOT running in a J2EE container.

ASKER CERTIFIED SOLUTION

JeremyGStein

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