[jboss-dev-forums] [Design of EJB 3.0] - Classloading problem in proxy factories

[bstansberry@jboss.com]

I'm testing proxy-clustered and am seeing a failure that looks like a problem in the core proxy module.

Test is doing a lookup of an SLSB; call to ProxyFactory to create the proxy fails:


  | javax.naming.NamingException: Could not dereference object [Root exception is java.lang.RuntimeException: Could not create the EJB3 Business Proxy implementing "org.jboss.ejb3.test.clusteredsession.ClusteredStatelessRemote" for clusteredStateless]
  | 	at org.jnp.interfaces.NamingContext.getObjectInstanceWrapFailure(NamingContext.java:1340)
  | 	at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:765)
  | 	at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:629)
  | 	at javax.naming.InitialContext.lookup(InitialContext.java:351)
  | 	at org.jboss.ejb3.test.clusteredsession.unit.StatelessUnitTestCase.testLoadbalance(StatelessUnitTestCase.java:72)
  | 	at junit.extensions.TestDecorator.basicRun(TestDecorator.java:24)
  | 	at junit.extensions.TestSetup$1.protect(TestSetup.java:23)
  | 	at junit.extensions.TestSetup.run(TestSetup.java:27)
  | Caused by: java.lang.RuntimeException: Could not create the EJB3 Business Proxy implementing "org.jboss.ejb3.test.clusteredsession.ClusteredStatelessRemote" for clusteredStateless
  | 	at org.jboss.ejb3.proxy.factory.session.SessionProxyFactoryBase.createProxyBusiness(SessionProxyFactoryBase.java:234)
  | 	at org.jboss.aop.Dispatcher.invoke(Dispatcher.java:121)
  | 	at org.jboss.aspects.remoting.AOPRemotingInvocationHandler.invoke(AOPRemotingInvocationHandler.java:82)
  | 	at org.jboss.remoting.ServerInvoker.invoke(ServerInvoker.java:908)
  | 	at org.jboss.remoting.transport.socket.ServerThread.completeInvocation(ServerThread.java:742)
  | 	at org.jboss.remoting.transport.socket.ServerThread.processInvocation(ServerThread.java:695)
  | 	at org.jboss.remoting.transport.socket.ServerThread.dorun(ServerThread.java:522)
  | 	at org.jboss.remoting.transport.socket.ServerThread.run(ServerThread.java:230)
  | Caused by: java.lang.LinkageError: loader constraints violated when linking org/jboss/ejb3/test/clusteredsession/NodeAnswer class
  | 	at java.lang.Class.getDeclaredConstructors0(Native Method)
  | 	at java.lang.Class.privateGetDeclaredConstructors(Class.java:2357)
  | 	at java.lang.Class.getConstructor0(Class.java:2671)
  | 	at java.lang.Class.getConstructor(Class.java:1629)
  | 	at org.jboss.ejb3.proxy.factory.ProxyFactoryBase.createProxyConstructor(ProxyFactoryBase.java:124)
  | 	at org.jboss.ejb3.proxy.factory.session.SessionProxyFactoryBase.createProxyBusiness(SessionProxyFactoryBase.java:212)
  | 	at org.jboss.aop.Dispatcher.invoke(Dispatcher.java:121)
  | 	at org.jboss.aspects.remoting.AOPRemotingInvocationHandler.invoke(AOPRemotingInvocationHandler.java:82)
  | 	at org.jboss.remoting.ServerInvoker.invoke(ServerInvoker.java:908)
  | 	at org.jboss.remoting.transport.socket.ServerThread.completeInvocation(ServerThread.java:742)
  | 	at org.jboss.remoting.transport.socket.ServerThread.processInvocation(ServerThread.java:695)
  | 	at org.jboss.remoting.transport.socket.ServerThread.dorun(ServerThread.java:522)
  | 	at org.jboss.remoting.transport.socket.ServerThread.run(ServerThread.java:230)
  | 	at org.jboss.remoting.MicroRemoteClientInvoker.invoke(MicroRemoteClientInvoker.java:206)
  | 	at org.jboss.remoting.Client.invoke(Client.java:1708)
  | 	at org.jboss.remoting.Client.invoke(Client.java:612)
  | 	at org.jboss.aspects.remoting.InvokeRemoteInterceptor.invoke(InvokeRemoteInterceptor.java:60)
  | 	at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)
  | 	at org.jboss.aspects.remoting.ClusterChooserInterceptor.invoke(ClusterChooserInterceptor.java:84)
  | 	at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)
  | 	at org.jboss.ejb3.proxy.remoting.IsLocalProxyFactoryInterceptor.invoke(IsLocalProxyFactoryInterceptor.java:72)
  | 	at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)
  | 	at org.jboss.aspects.remoting.ClusteredPojiProxy.invoke(ClusteredPojiProxy.java:79)
  | 	at $Proxy2.createProxyBusiness(Unknown Source)
  | 	at org.jboss.ejb3.proxy.objectfactory.session.SessionProxyObjectFactory.createProxy(SessionProxyObjectFactory.java:129)
  | 	at org.jboss.ejb3.proxy.clustered.objectfactory.session.SessionClusteredProxyObjectFactory.getProxy(SessionClusteredProxyObjectFactory.java:76)
  | 	at org.jboss.ejb3.proxy.objectfactory.ProxyObjectFactory.getObjectInstance(ProxyObjectFactory.java:146)
  | 	at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:304)
  | 	at org.jnp.interfaces.NamingContext.getObjectInstance(NamingContext.java:1315)
  | 	at org.jnp.interfaces.NamingContext.getObjectInstanceWrapFailure(NamingContext.java:1332)
  | 	at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:765)
  | 	at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:629)
  | 	at javax.naming.InitialContext.lookup(InitialContext.java:351)
  | 	at org.jboss.ejb3.test.clusteredsession.unit.StatelessUnitTestCase.testLoadbalance(StatelessUnitTestCase.java:72)
  | 	at junit.extensions.TestDecorator.basicRun(TestDecorator.java:24)
  | 	at junit.extensions.TestSetup$1.protect(TestSetup.java:23)
  | 	at junit.extensions.TestSetup.run(TestSetup.java:27)
  | 

Failure is coming in the SessionProxyFactoryBase code that attempts to replace the cached proxy constructor with one created using the TCCL:


  |          // Obtain the correct business proxy constructor
  |          Constructor<?> constructor = this.getConstructorsProxySpecificBusinessInterface().get(
  |                businessInterfaceName.trim());
  | 
  |          /*
  |           * In place for web injection (isolated CL)
  |           */
  |          ClassLoader tcl = Thread.currentThread().getContextClassLoader();
  |          try
  |          {
  |             // See if we can get at the bean class from the TCL
  |             Class<?> businessInterfaceClass = Class.forName(businessInterfaceName, false, tcl);
  | 
  |             // If so, use the TCL to generate the Proxy class, not the Container CL
  |             Set<Class<?>> businessInterfaces = new HashSet<Class<?>>();
  |             businessInterfaces.add(businessInterfaceClass);
  |             constructor = this.createProxyConstructor(businessInterfaces, tcl);
  | 
  |          }
  |          catch (ClassNotFoundException cce)
  |          {
  |             // Ignore
  |          }
  | 

The business interface is simple:


  | public interface ClusteredStatelessRemote
  | {
  |    NodeAnswer getNodeState();
  | }
  | 

It's odd to me that Class.forName() is able to load the ClusteredStatelessRemote class using the TCCL, and a nested call to Proxy.getProxyClass(...) passing the classloader and the interface is able to generate a proxy class, yet there is a LinkageError trying to find the constructor.

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