Jndi communication between app servers?

Question

Hi all,
I'm quite familiar with J2EE and its communication architecture. In the past, I haven't had the need to communicate from one app server to another (just all web/applet clients to the central app server). But now I need to :)
Is there a way to communicate (synchronously) between app servers on different machines that aren't clustered? Clustering is not a possibility.
I know JMS is an option, but JMS is asyncrhonous. I also know you can't create server sockets in an app server because the J2EE spec disallows this approach, so forget about client/server communication via sockets.
This would be my ideal solution:
Server A does a jndi lookup for a bean on server B. Server A gets this reference and works with it just like any other J2EE client to server B.
Does JNDI allow you to do lookups to other namespaces outside of the current namespace on server A?
Can this even be done?
Thanks,
Les Hazlewood

Answer 1

Yes. It's possible. For one of my applications, I have three HP-UX servers that run i2 software on them, but for different business units. I have a J2EE application that does a little bit of everything for the i2 applications. Since the business logic is the same, with only the business dept differing, I deployed 3 instances of JBoss, each running on their own server. My user's log into one of the applications, doesn't matter which, and if they request a service (EJB) that needs to run on a different server, my webapp makes a connection to that server and uses the remote EJB to do the work. It's very possible and an excellent solution.
The solution will depend on which J2EE server you're using.
Here's a class I use to retrieve the InitialContext I need for my application:
package com.cibavision;
import javax.naming.InitialContext;
import javax.naming.Context;
import javax.naming.NamingException;
import java.rmi.RemoteException;
import java.util.Properties;
public class CibaJNDI{
   public static InitialContext getInitialContext ( String server ) throws javax.naming.NamingException {
      Properties p = new Properties () ;
      p.put(Context.INITIAL_CONTEXT_FACTORY,
             "org.jnp.interfaces.NamingContextFactory");
      p.put(Context.PROVIDER_URL,
             "jnp://" + server + ":1099");
      p.put(Context.URL_PKG_PREFIXES,
             "org.jboss.naming:org.jnp.interfaces");
      return new InitialContext (p) ;
}Using this class, I have logic in my application that calls for the appropriate server, something like this:
if businessA then use server1
if businessB then use server2
if businessC then use server3
I then call for my InitialContext, request my EJB, and I'm off and running. No clustering, it matters which machine I'm on (I have to read extract files, etc.)
Works great. We are also a weblogic shop, but I haven't made any calls to weblogic from outside my J2EE app yet, but it should only differ by the hash attributes you pass to new InitialContext( props ).
Hope this helps,
Perry Tew