4:29 p.m.
Mike Miller [https://community.jboss.org/people/mikemil] created the discussion
"Problems using the @RemoteHome annotation for backward compatibility"
To view the discussion, visit: https://community.jboss.org/message/799738#799738
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We are (hopefully) coming to the end of our migration from EJB 2.1 to EJB 3
"exercise". We are encountering ClassCastExceptions when we try to load an
EJB3 bean from one of our older, yet to be migrated EJB2.1 server instances. If I
understood the 3.0 spec correctly, 3.0 can be a 'client' of 2.1 but not really
vise versa.
Little bit of history - our product is a POS where we have a 'store server' at
each retail store and a 'Central' server at company headquarters. This can NOT
be big banged over night, so our migration/upgrade path means that Central will be
upgraded to 3.0 first, then sets of stores will be upgraded, but not all at once. Most of
the communication between servers is done thru JMS, but we do have some cases where we
make what we call a 'reverse service call' which means a store loads an EJB from
the Central Server's JNDI, or Central loads an EJB from the Store servers JNDI. This
is where we are at right now. Central at 3.0 and Store at 2.1, then Store requests an EJB
from Central and when we attempt to PortableNarrow - we get a ClassCastException.
We are doing this on JBoss 4.2.3.GA.
If I understand the documentation correctly, it sounds like we should be able to use the
@RemoteHome to generate the home interface for the 2.1 clients to use to talk to our
Central Server. I have tried this and assume that I am missing some piece of the puzzle.
I have tried to compare mine agains the ejb21_client_adaptors sample in the EJB3 tutorial
files but it's not working. The exception we get on the Store server side is below:
{code}
2013-02-26 13:33:00,985 ERROR [root] java.lang.RuntimeException: problem connecting to EJB
container
at
com.jda.portfolio.infrastructure.base.service.ServiceFactory.getRemoteService(ServiceFactory.java:503)
at
com.jda.portfolio.infrastructure.base.service.ServiceFactory$CentralServerLookupThread.run(ServiceFactory.java:621)
2013-02-26 13:33:00,989 ERROR [root] Caused by: null
java.lang.ClassCastException
at
com.sun.corba.se.impl.javax.rmi.PortableRemoteObject.narrow(PortableRemoteObject.java:245)
at javax.rmi.PortableRemoteObject.narrow(PortableRemoteObject.java:153)
at
com.jda.portfolio.infrastructure.base.service.ServiceFactory.getRemoteService(ServiceFactory.java:488)
at
com.jda.portfolio.infrastructure.base.service.ServiceFactory$CentralServerLookupThread.run(ServiceFactory.java:621)
Caused by: java.lang.ClassCastException: $Proxy1238 cannot be cast to
org.omg.CORBA.Object
at
com.sun.corba.se.impl.javax.rmi.PortableRemoteObject.narrow(PortableRemoteObject.java:228)
... 3 more
2013-02-26 13:33:00,991 ERROR [root] Root cause: $Proxy1238 cannot be cast to
org.omg.CORBA.Object
java.lang.ClassCastException: $Proxy1238 cannot be cast to org.omg.CORBA.Object
at
com.sun.corba.se.impl.javax.rmi.PortableRemoteObject.narrow(PortableRemoteObject.java:228)
at javax.rmi.PortableRemoteObject.narrow(PortableRemoteObject.java:153)
at
com.jda.portfolio.infrastructure.base.service.ServiceFactory.getRemoteService(ServiceFactory.java:488)
{code}
Below are snippets from our classes
*EJB3 Session Bean*
{code}
package com.jda.portfolio.pos.server.service.security;
...
@Stateless
@RemoteHome(KeyManagementServiceHome.class)
@RemoteBinding(jndiBinding="ejb/KeyManagementService")
@LocalBinding(jndiBinding="ejb/KeyManagementServiceLocal")
@TransactionManagement(TransactionManagementType.CONTAINER)
@TransactionAttribute(TransactionAttributeType.REQUIRED)
public class KeyManagementServiceBean extends
com.jda.portfolio.infrastructure.server.service.AbstractService implements
KeyManagementService, KeyManagementServiceLocal
{
@Init
public void ejbCreate() {
System.out.println("**** ejbCreate() of " + this.getClass() + "
called ****");
}
...
}
{code}
*New Home interface for 2.1 clients*
{code}
package com.jda.portfolio.pos.server.service.security;
...
public interface KeyManagementServiceHome extends EJBHome {
public KeyManagementServiceRemote create() throws CreateException,
RemoteException;
}
{code}
*Remote interface created by Home*
{code}
package com.jda.portfolio.pos.server.service.security;
import javax.ejb.EJBObject;
public interface KeyManagementServiceRemote extends EJBObject {
public int addKey( com.jda.portfolio.infrastructure.base.util.KeyGenData
keyGenData ) ;
public boolean publishKeys( java.util.List locationNumbers ) ;
public int removeKeys( java.util.List keysToRemove ) ;
}
{code}
Using no deployment descriptors. After making this change, I did dump the JNDIView for my
Central (3.0) server from the console and noticed one strange entry that does not show up
in our other servers. There is an entry that looks like a subcontext of
"KeyManagementServiceBean" with a named pair of 'home' : $Proxy1256.
The KeyManagementServiceBean is actually the name of the class for the EJB Session bean I
am trying to make available as a 2.1 bean.
Setting breakpoints in the Store server where we are loading and attempting to narrow the
reference - I also noticed that the class within the proxy class is usually
'ClientContainer' when things work, like for 2.1 - but when we load the 3.0 bean
from Central, the class name in the proxy is StatelessRemoteProxy. Not sure if that means
anything or just a result of the different implementations.
I know there's a lot of info here but I can help clarify it if it is not clear.
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