Exception: Cannot narrow remote object to ...

Question

Hi,
          in certain circumstances I get an Exception "Cannot narrow remote
          object to <some EJB-Home-Class>".
          My enviroment: weblogic 7.0, solaris, Java 1.3.1, J2EE-application
          (EJBs, Servlets, Database)
          In the init method of an start-up servlet I spawn some threads for a
          scheduler of the application. There are a scheduler core and some
          worker classes.
          The start-up servlet, all the other servlets and the schedulers
          classes are in an web-archive (war-file) in an ear-archiv. Furthermore
          there a some 3rd party archives in the ear-archive, a jndi.properties
          file etc. The manifest file of the war-archive contains a class-path,
          points to the 3rd party archives in the ear-archive.
          The schedulers workers code is simple:
          InitialContext jndiContext = ...getInitialContext();
          Object obj = jndiContext.lookup(<some EJB>);
          - EJBs home interface (for example):
          SyncOrderQueueHome home = (SyncOrderQueueHome)
          javax.rmi.PortableRemoteObject.narrow(obj,
          SyncOrderQueueHome.class);
          - EJBs remote interface:SyncOrderQueue sync = home.create();
          - call some business method
          sync.createOrderQueue();
          In the enviroment described above I get an " Exception: Cannot narrow
          remote object to <package>.SyncOrderQueueHome".
          On the other hand the scheduler and all the workers work fine as a
          standalone application (not in an app-server context) and in Oracles
          app-server (OC4J, v.9.0.3).
          I tried to understand, what for an object I get as the result of the
          JNDI lookup bevore the narrow method fails:
          - in the app-servers context:
          <package>.SyncOrderQueueEJB_4o6qkf_HomeImpl
          - outside the app-server:
          <package>.SyncOrderQueueEJB_4o6qkf_HomeImpl_WLStub
          What happened here? The common servlets use the same functionality and
          work fine. Why I get different objects? Where is the bug?
          Any ideas?
          Thomas
          

Answer 1

I believe the problem is the threads you are starting are not using the
          context classloader of the current thread.
          -- Rob
          [email protected] wrote:
          > Hi,
          >
          > in certain circumstances I get an Exception "Cannot narrow remote
          > object to <some EJB-Home-Class>".
          >
          > My enviroment: weblogic 7.0, solaris, Java 1.3.1, J2EE-application
          > (EJBs, Servlets, Database)
          >
          > In the init method of an start-up servlet I spawn some threads for a
          > scheduler of the application. There are a scheduler core and some
          > worker classes.
          > The start-up servlet, all the other servlets and the schedulers
          > classes are in an web-archive (war-file) in an ear-archiv. Furthermore
          > there a some 3rd party archives in the ear-archive, a jndi.properties
          > file etc. The manifest file of the war-archive contains a class-path,
          > points to the 3rd party archives in the ear-archive.
          >
          > The schedulers workers code is simple:
          >
          > InitialContext jndiContext = ...getInitialContext();
          > Object obj = jndiContext.lookup(<some EJB>);
          >
          > - EJBs home interface (for example):
          > SyncOrderQueueHome home = (SyncOrderQueueHome)
          > javax.rmi.PortableRemoteObject.narrow(obj,
          > SyncOrderQueueHome.class);
          >
          > - EJBs remote interface:SyncOrderQueue sync = home.create();
          >
          > - call some business method
          > sync.createOrderQueue();
          > In the enviroment described above I get an " Exception: Cannot narrow
          > remote object to <package>.SyncOrderQueueHome".
          >
          > On the other hand the scheduler and all the workers work fine as a
          > standalone application (not in an app-server context) and in Oracles
          > app-server (OC4J, v.9.0.3).
          >
          > I tried to understand, what for an object I get as the result of the
          > JNDI lookup bevore the narrow method fails:
          > - in the app-servers context:
          > <package>.SyncOrderQueueEJB_4o6qkf_HomeImpl
          > - outside the app-server:
          > <package>.SyncOrderQueueEJB_4o6qkf_HomeImpl_WLStub
          >
          > What happened here? The common servlets use the same functionality and
          > work fine. Why I get different objects? Where is the bug?
          >
          > Any ideas?
          > Thomas