LoadBalance in InitialContext Lookup

Question

Hi,
I'm having following requirement.An Ejb has been deplyed in a weblogic cluster which has two Servers Server A & B.
In Server A the Ejb is in started mode,& in Server B it is in Stopped state.Now from the server B i'm using a standalone client to lookup the ejb using JNDI name & initial context.
+          Hashtable env = new Hashtable();+
+          env.put( javax.naming.Context.INITIAL_CONTEXT_FACTORY , "weblogic.jndi.WLInitialContextFactory" );+
+          env.put( javax.naming.Context.PROVIDER_URL , "t3://SERVERB:9001,SERVERA:9001" );+
+          ctx = new InitialContext( env );+
I had given two URL's [ both Server A & Server B] in the initialcontext. What I'm expecting is the initialcontext will lookup serverB where the EJB is in stopped state, then it will lookup in Server A where the EJB is in started stated & communicate with it.
But now i'm getting the exception, it is throw from ServerB where the EJB is in Stopped state.
+Exception in thread "main" javax.naming.NameNotFoundException: Unable to resolve 'XXXEngineBean'. Resolved '' [Root exception is javax.naming.NameNotFoundException: Unable to resolve 'XXXEngineBean'. Resolved '']; remaining name 'XXXEngineBean'+
+     at weblogic.rjvm.ResponseImpl.unmarshalReturn(ResponseImpl.java:234)+
Thanks in Advance

Answer 1

Hi,
this may be the same implementation problem of class loading inside SAP NetWeaver Java we stumled oger. I posted an OSS but they will not change it.
If you have to EJBs in different enterprise applications, you MUST set an application reference from one enterprise application "A" (typically the calling with the lookup) to the enterprise application "B" that contains the EJB that is looked up.
see [http://help.sap.com/saphelp_nw73/helpdata/en/4a/ee99c229370c9ee10000000a42189c/content.htm]
"To look up a remote object, you must have its remote interface in the clientu2019s class path (for external clients) or have a class loader reference to it (for components and applications running on the server process)."
This makes the class loader of "B" the parent class loader of "A". If you omit this reference, the object that is returned by the lookup is loaded by class loader of "B" and you try to cast it to the class of class loader "A" which of course fails.
Even calling
PortableRemoteObject.narrow(obj, MyEjbLocalHome .class);
before the class cast does not help (because it does nothing to obj at all).
How do you set an application reference?
In META-INF/application-j2ee-engine.xml in enterprise applicatoin "A" enter
<?xml version="1.0" encoding="UTF-8"?>
<application-j2ee-engine xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="application-j2ee-engine.xsd">
  <reference reference-type="hard">
    <reference-target provider-name="VENDOR_NAME_OF_EAR_B" target-type="application">APP_NAME_OF_EAR_B</reference-target>
  </reference>
</application-j2ee-engine>
If you are working with Development Components, just add a dependency with "Runtime" and this is done automatically.
BTW if you redeploy "B", "A" will be restarted because its parent class loader changed.
Regards
Rolf