Glassfish EJB Remote Interface Multithreaded Application - glassfish

Question

I have a multithreaded Java SWT application that connects to a remote stateless bean for some data processing. I am running Glassfish 3.1.1 (build 12) on a Windows 7 32-bit OS under jdk 1.7.0_02.
For each thread accessing the EJB I create a new remote interface object, for example for 2 threads executing in parallel I have,
Thread-1
LoginBeanRemote ejbClient = (LoginBeanRemote) new InitialContext().lookup("LoginBean");
ejbClient.doSomething();
Thread-2
LoginBeanRemote ejbClient = (LoginBeanRemote) new InitialContext().lookup("LoginBean");
ejbClient.doSomethingDifferent();
Now it runs fine half of the time and gives a 'NullPointerException' on the second line for the rest of the time.
SEVERE: java.lang.NullPointerException
at com.mypackage.myclass.getListofOperators(LoginBean.java:270)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.glassfish.ejb.security.application.EJBSecurityManager.runMethod(EJBSecurityManager.java:1052)
at org.glassfish.ejb.security.application.EJBSecurityManager.invoke(EJBSecurityManager.java:1124)
at com.sun.ejb.containers.BaseContainer.invokeBeanMethod(BaseContainer.java:5366)
at com.sun.ejb.EjbInvocation.invokeBeanMethod(EjbInvocation.java:619)
at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800)
at com.sun.ejb.EjbInvocation.proceed(EjbInvocation.java:571)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doAround(SystemInterceptorProxy.java:162)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.aroundInvoke(SystemInterceptorProxy.java:144)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at com.sun.ejb.containers.interceptors.AroundInvokeInterceptor.intercept(InterceptorManager.java:861)
at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800)
at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:370)
at com.sun.ejb.containers.BaseContainer.__intercept(BaseContainer.java:5338)
at com.sun.ejb.containers.BaseContainer.intercept(BaseContainer.java:5326)
at com.sun.ejb.containers.EJBObjectInvocationHandler.invoke(EJBObjectInvocationHandler.java:206)
at com.sun.ejb.containers.EJBObjectInvocationHandlerDelegate.invoke(EJBObjectInvocationHandlerDelegate.java:79)
at $Proxy180.getListofOperators(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at com.sun.corba.ee.impl.presentation.rmi.ReflectiveTie.dispatchToMethod(ReflectiveTie.java:144)
at com.sun.corba.ee.impl.presentation.rmi.ReflectiveTie._invoke(ReflectiveTie.java:174)
at com.sun.corba.ee.impl.protocol.CorbaServerRequestDispatcherImpl.dispatchToServant(CorbaServerRequestDispatcherImpl.java:528)
at com.sun.corba.ee.impl.protocol.CorbaServerRequestDispatcherImpl.dispatch(CorbaServerRequestDispatcherImpl.java:199)
at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleRequestRequest(CorbaMessageMediatorImpl.java:1624)
at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleRequest(CorbaMessageMediatorImpl.java:1486)
at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleInput(CorbaMessageMediatorImpl.java:990)
at com.sun.corba.ee.impl.protocol.giopmsgheaders.RequestMessage_1_2.callback(RequestMessage_1_2.java:214)
at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleRequest(CorbaMessageMediatorImpl.java:742)
at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.dispatch(CorbaMessageMediatorImpl.java:539)
at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.doWork(CorbaMessageMediatorImpl.java:2324)
at com.sun.corba.ee.impl.orbutil.threadpool.ThreadPoolImpl$WorkerThread.performWork(ThreadPoolImpl.java:497)
at com.sun.corba.ee.impl.orbutil.threadpool.ThreadPoolImpl$WorkerThread.run(ThreadPoolImpl.java:540)
SEVERE: at com.mypackage.myclass.getListofOperators(LoginBean.java:270)
SEVERE: at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
SEVERE: at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
SEVERE: at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
SEVERE: at java.lang.reflect.Method.invoke(Method.java:601)
SEVERE: at org.glassfish.ejb.security.application.EJBSecurityManager.runMethod(EJBSecurityManager.java:1052)
SEVERE: at org.glassfish.ejb.security.application.EJBSecurityManager.invoke(EJBSecurityManager.java:1124)
SEVERE: at com.sun.ejb.containers.BaseContainer.invokeBeanMethod(BaseContainer.java:5366)
SEVERE: at com.sun.ejb.EjbInvocation.invokeBeanMethod(EjbInvocation.java:619)
SEVERE: at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800)
SEVERE: at com.sun.ejb.EjbInvocation.proceed(EjbInvocation.java:571)
SEVERE: at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doAround(SystemInterceptorProxy.java:162)
SEVERE: at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.aroundInvoke(SystemInterceptorProxy.java:144)
SEVERE: at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
SEVERE: at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
SEVERE: at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
SEVERE: at java.lang.reflect.Method.invoke(Method.java:601)
SEVERE: at com.sun.ejb.containers.interceptors.AroundInvokeInterceptor.intercept(InterceptorManager.java:861)
SEVERE: at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800)
SEVERE: at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:370)
SEVERE: at com.sun.ejb.containers.BaseContainer.__intercept(BaseContainer.java:5338)
SEVERE: at com.sun.ejb.containers.BaseContainer.intercept(BaseContainer.java:5326)
SEVERE: at com.sun.ejb.containers.EJBObjectInvocationHandler.invoke(EJBObjectInvocationHandler.java:206)
SEVERE: at com.sun.ejb.containers.EJBObjectInvocationHandlerDelegate.invoke(EJBObjectInvocationHandlerDelegate.java:79)
SEVERE: at $Proxy180.getListofOperators(Unknown Source)
SEVERE: at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
SEVERE: at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
SEVERE: at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
SEVERE: at java.lang.reflect.Method.invoke(Method.java:601)
SEVERE: at com.sun.corba.ee.impl.presentation.rmi.ReflectiveTie.dispatchToMethod(ReflectiveTie.java:144)
SEVERE: at com.sun.corba.ee.impl.presentation.rmi.ReflectiveTie._invoke(ReflectiveTie.java:174)
SEVERE: at com.sun.corba.ee.impl.protocol.CorbaServerRequestDispatcherImpl.dispatchToServant(CorbaServerRequestDispatcherImpl.java:528)
SEVERE: at com.sun.corba.ee.impl.protocol.CorbaServerRequestDispatcherImpl.dispatch(CorbaServerRequestDispatcherImpl.java:199)
SEVERE: at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleRequestRequest(CorbaMessageMediatorImpl.java:1624)
SEVERE: at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleRequest(CorbaMessageMediatorImpl.java:1486)
SEVERE: at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleInput(CorbaMessageMediatorImpl.java:990)
SEVERE: at com.sun.corba.ee.impl.protocol.giopmsgheaders.RequestMessage_1_2.callback(RequestMessage_1_2.java:214)
SEVERE: at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleRequest(CorbaMessageMediatorImpl.java:742)
SEVERE: at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.dispatch(CorbaMessageMediatorImpl.java:539)
SEVERE: at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.doWork(CorbaMessageMediatorImpl.java:2324)
SEVERE: at com.sun.corba.ee.impl.orbutil.threadpool.ThreadPoolImpl$WorkerThread.performWork(ThreadPoolImpl.java:497)
SEVERE: at com.sun.corba.ee.impl.orbutil.threadpool.ThreadPoolImpl$WorkerThread.run(ThreadPoolImpl.java:540)
Also the exception not always comes from the same thread, it can be either ejbClient.doSomething() or ejbClient.doSomethingDifferent()
I am not using injection for entitymanager as I need to provide different username and passwords for different sessions and do it as
properties.put("javax.persistence.jdbc.user", loginName);
properties.put("javax.persistence.jdbc.password", password);
properties.put("javax.persistence.jdbc.url", "jdbc:oracle:thin:#127.0.0.1:1521:ORCL");
properties.put("javax.persistence.jdbc.driver", "oracle.jdbc.driver.OracleDriver");
EntityManagerFactory emf = Persistence.createEntityManagerFactory("xadp", properties);
EntityManager em = emf.createEntityManager(properties);
Any ideas?

Answer 1

Without seeing more of the code I can only guess, but it is likely you are using instance variables in your session bean.
The thing about session beans is that, even with a Stateless session bean, the container (in this case Glassfish) can pool the beans. That means it has many instances of a session bean to service requests and shares them among the clients.
The key point is that a session bean can be given to another client at any time, so if you save state in the bean in an instance or static field, you might have client A make a call and then get interrupted halfway, so client B sees client A's data.