invoking an EJB over iiop

[hibsmax]

Hi, folks.

I've tried a couple of other forums with this issue but no traction, so here I am to tickle your brains. :)

I have a servlet that makes calls to an EJB on another server using iiop. I've been trying for days but I still cannot get it to work. My current issue is that when I access the servlet it gets an initial context and performs a lookup for the EJB which returns this:
12:23:00,104 ERROR [STDERR] java.lang.ClassCastException
12:23:00,104 ERROR [STDERR] at com.sun.corba.se.impl.javax.rmi.PortableRemoteObject.narrow(PortableRemoteObject.java:229)

For my INITIAL_CONTEXT_FACTORY I am using:
org.jboss.iiop.naming.ORBInitialContextFactory

This is the same class as I am specifying in my server's jndi.properties.

Here are the steps being taken by the servlet:
1. create a Properties object
2. put the initial context factory class name i.e. org.jboss.iiop.naming.ORBInitialContextFactory
3. put URL of the server where the EJB lives i.e. iiop:/server:3528
4. create a new InitialContext using the above Properties object.
5. once I have the InitialContext, I perform a lookup using the EJB name i.e. "iiop://my.EJBHome"
6. I added a debug statement to the code and note that the Object returned by the lookup is : com.sun.jndi.cosnaming.CNCtx

My understanding is that the EJB JAR doesn't need any stubs, etc. they are supposed to be created on at runtime. So I must be doing something wrong but I dont' know what. I also understand that JBoss iiop is supposed to be enabled when you use the all configuration which is what I am using. I don't know of any additional configuration changes that need to be made, if any. This type of work is new to me, I don't have experience with EJBs on any other application server platform to fall back on. Can anyone suggest any know traps that a newbie might fall into? My clientside WAR file does not contain the EJB classes, just the interfaces (I found that problem in another thread). I can't find a lab or tutorial for this on JBoss 4.2 GA so I have no reference. I can't find an answer on google and the books I have (O'Reilly and JBoss admin guide) don't discuss this topic.

peace, Anders

[jaikiran]

How are you application(s) packaged? Are the EJB jar and the war file, two separate applications or are they part of an ear file?

Also, do have a look at this wiki page (if you havent already seen that ) http://wiki.jboss.org/wiki/Wiki.jsp?page=ClassCastExceptions


Additionally, in your code try using some debug statements like:

// lookup you ejb
Object obj = ctx.lookup(".....");
// i guess this is going to output Proxy$ or something similar
System.out.println("Returned obj is of class: " + obj.getClass());

// now lets see whether we can narrow that object
if (obj instanceof MyHome ) {
//where MyHome is the class name of the bean's home
 System.out.println("Everything looks fine. Lets do the PortableRemoteObject.narrow");
 MyHome home = (MyHome) PortableRemoteObject.narrow(obj,MyHome.class);
 System.out.println("Success");
 } else {
 System.out.println("Most probably a classloader issue");
 System.out.println("Object returned was loaded by: " + obj.getClass().getClassLoader());
 System.out.println("MyHome class in the servlet was loaded by: " + MyHome.class.getClassLoader());
 }

P.S.: I havent tried this code, you might have to do any changes that are required. But it might just give you some options to try out.

[jaikiran]

I added a debug statement to the code and note that the Object returned by the lookup is : com.sun.jndi.cosnaming.CNCtx

This doesnt look right to me. Are you using the right jndi name to lookup your bean? Can you post the code?

[hibsmax]

Thanks for your reply, jaikiran!

The servlet is packaged in a WAR file and is deployed on server1.

The EJB is packaged in a JAR file and is deployed on server2.

The jndi-name in jboss.xml and ejb-jar.xml is set to interop.InteropHome. Here's jboss.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE jboss PUBLIC "-//JBoss//DTD JBOSS 4.0//EN" "http://www.jboss.org/j2ee/dtd/jboss_4_2.dtd">
<jboss>
 <enterprise-beans>
 <session>
 <ejb-name>interop.InteropBean</ejb-name>
 <invoker-bindings>
 <invoker>
 <invoker-proxy-binding-name>iiop</invoker-proxy-binding-name>
 </invoker>
 <jndi-name>interop.InteropHome</jndi-name>
 </invoker-bindings>
 </session>
 </enterprise-beans>
</jboss>

My ejb-jar.xml contains the exact same jndi-name.

Here's how I create the initial context:

Properties h = new Properties();
 String ctx = "";
 ctx = "org.jboss.iiop.naming.ORBInitialContextFactory";
 h.put( Context.INITIAL_CONTEXT_FACTORY, ctx );
 h.put( Context.PROVIDER_URL, url );
 InitialContext initCtx = new InitialContext(h);
 return initCtx;

The URL I am using is:

iiop://server2:3528

Finally, here's the EJB lookup:

Object foo = getInitialContext(url, user, password).lookup(ejbHomeName);
 Object bar = PortableRemoteObject.narrow( foo, InteropHome.class );
 home = (InteropHome) bar;

In my source code I use this for the EJB name:

iiop://interop.InteropHome

user and password are null in this case. When I run this code and display the class name of the object in foo, I get :

com.sun.jndi.cosnaming.CNCtx

[hibsmax]

When I change the EJB Home name in the source code i.e.

FROM : iiop://interop.InteropHome
TO : interop.InteropHome

I get this message when I try and call the bean:

javax.naming.NameNotFoundException: interop.InteropHome

I don't know if that gives you any more info?

Peace, Anders

[hibsmax]

I added the classloader System.outs specified above and I get this output when trying to access the EJB:

11:46:07,954 INFO [STDOUT] Object returned was loaded by: org.jboss.mx.loading.UnifiedClassLoader3@115875d{ url=null ,addedOrder=2}
11:46:07,954 INFO [STDOUT] MyHome class in the servlet was loaded by: WebappClassLoader
 delegate: false
 repositories:
 /WEB-INF/classes/
----------> Parent Classloader:
java.net.FactoryURLClassLoader@41254ec

I get this result when I perform the EJB lookup using this:

iiop://server1:3528/interop.InteropHome

when I was simply using

iiop://interop.InteropHome

I was getting a message like this:

11:26:12,021 WARN [address] init_host, interop.InteropHome unresolvable

when I googled that message, minus the interop.InteropHome text, I found a link to some jacorb source code and found that for interop.InteropHome to appear in the warning message, the code thinks that I am specifying a URL and it's trying to determine the host addr. That led me to believe that the lookup for the EJB required me to add server and host information. I don't know if that's true but when I added it I got a different error. This time I got a NullPointerException in my servlet but there is no line information telling me where the error is. However, because of other debug statements in my code I can tell that it is the following statement:

Object bar = PortableRemoteObject.narrow( foo, InteropHome.class );

foo isn't null so I don't know why that exception is being thrown, it must be something deeper.

[hibsmax]

Actually the NullPointerException is being caused by this line of code which appears immediately after the call to PortableRemoteObject.narrow:

System.out.println("Class bar is : " + bar.getClass().getName());

I guess that means the call to narrow is failing.

[hibsmax]

when I change the ejb lookup name to iiop/interop.InteropHome, I get class

org.omg.stub.javax.ejb._EJBHome_Stub

returned by the lookup. That looks a little more promising.

[hibsmax]

The latest errors I am seeing are:

13:47:38,057 ERROR [orb] no adapter activator exists for EJBHome&%interop.InteropHome
13:47:38,067 INFO [STDOUT] Class home is : class org.omg.stub.javax.ejb._EJBHome_Stub

I googled the no adapter activator message and found some evidence (a post on a mailing list) to suggest that it's not really a problem.

[hibsmax]

I just wanted to add the following stdout from my backend server to show that the EJB is being deployed as expected.

15:22:42,381 INFO [EjbModule] Deploying interop.InteropBean
15:22:42,880 INFO [InteropBean] EJBHome reference for interop.InteropHome:
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
15:22:42,881 INFO [InteropBean] Home IOR for interop.InteropBean bound to iiop/interop.InteropHome in JNP naming service
15:22:42,883 INFO [InteropBean] Home IOR for interop.InteropBean bound to interop.InteropHome in CORBA naming service

[jaikiran]

15:22:42,881 INFO [InteropBean] Home IOR for interop.InteropBean bound to iiop/interop.InteropHome
in JNP naming service
15:22:42,883 INFO [InteropBean] Home IOR for interop.InteropBean bound to interop.InteropHome in CO
RBA naming service

You seem to have made good progress :) Where's it that you are currently stuck at? I havent tried IIOP before so not sure what the exact issue might be. Could you do the following on the server2 where your bean is deployed:

- Go to http://localhost:8080/jmx-console
- Search for service=JNDIView
- Click on that link
- On the page that comes up, click on the Invoke button beside the list() method
- The page that comes up will show the contents of the JNDI tree. This will show you the jndi names and the objects that are bound to those names.
- Post the output

[hibsmax]

That generates a lot of output so here is the EJB-related stuff. Let me know if you would like to see the rest:

Ejb Module: InteropBean.jar

java:comp namespace of the interop.InteropBean bean:

 +- HandleDelegate (class: org.jboss.proxy.ejb.handle.HandleDelegateImpl)
 +- UserTransaction (class: javax.transaction.UserTransaction)
 +- ORB (class: org.jacorb.orb.ORB)
 +- env (class: org.jnp.interfaces.NamingContext)

There's also a reference to my EJB in the Global JNDI Namespace:

Global JNDI Namespace

 +- iiop (class: org.jnp.interfaces.NamingContext)
 | +- interop.InteropHome (class: javax.ejb.EJBHome)

[hibsmax]

To answer your question, "where am I stuck at?", well, that varies as I try different things. I seem to be able to startup both the front end and back end servers without any issues but when the front end servlet tries to lookup the EJB, I get the errors. The errors change depending on what settings I am currently using.

It's a shame you haven't used IIOP before because what I think would really help me is a concrete example of a servlet communicating with an EJB over iiop. I haven't been able to find one though. I think if I had a working example I could figure out where I am going wrong. I think that my problem lies with one or more of these:
1. my jndi.properties,
2. my jacorb.properties,
3. my InitialContext as defined in my servlet,
4. my EJB lookup in the servlet.

Everything I have read discusses how JBoss doesn't need stubs and skeletons making the deployment easier. I agree that skipping a compilation step does make the process easier but I still think there needs to be something explaining the required configuration.

Peace, Anders

[jaikiran]

The JNDI view looks good to me. You might have already seen this http://labs.jboss.com/jbossiiop/. If not, then see if you can get hold of the testcases that are mentioned there. They also mention

If you are using JDK 1.4 or newer, your client-side jndi.properties file should look like this:

java.naming.factory.initial=com.sun.jndi.cosnaming.CNCtxFactory
java.naming.provider.url=corbaloc::server.host.name:3528/JBoss/Naming/root

You might want to try passing

h.put( Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.cosnaming.CNCtxFactory");

Sorry, i am not being of much help - havent tried my hands at this stuff earlier

[hibsmax]

Thanks, jaikiran.

I had found that lab and noted that it deals with JBoss 3.2. I am downloading the source for 4.2GA to see if similar test cases still exist. I don't believe there is a similar lab for 4.2 (at least I cannot find it).

I tried the recommended jndi.properties settings but that just gave me errors when I started up JBoss.

As a last gasp I have contacted one of the people mentioned in that lab directly. I don't know if that is the correct thing to do but google has dried up. :)

Peace, Anders