NullPointerException when accessing EntityManager on Websphere

I have following code.

public class PersistableProcessStepStatus extends ProcessStepStatus {
  @PersistenceContext(unitName = "primary")
  private EntityManager entityManager;    
  private void changeFlag(String namedQuery, String flag, boolean enable) {
                getEntityManager().createNamedQuery(namedQuery)
                                .setParameter("a", prozessName)
                                .setParameter("b", vorgangName)
                                .setParameter(flag, enable).executeUpdate();
        }
  [...]
}

I call my method over JMX console and it goes down to changeFlag method where exception is thrown. Entity manager works in other parts of my application. This application runs on Websphere 8.5.5.1

I haven't found source code of JPATxEntityManager, so I really do not know how to process.

Here is the exception which is thrown by calling createNamedQuery method.

[30/10/14 15:18:34:805 CET] 000002a7 SystemErr     R java.lang.NullPointerException
[30/10/14 15:18:34:805 CET] 000002a7 SystemErr     R    at com.ibm.ws.jpa.management.JPATxEntityManager.getEMInvocationInfo(JPATxEntityManager.java:218)
[30/10/14 15:18:34:805 CET] 000002a7 SystemErr     R    at com.ibm.ws.jpa.management.JPATxEntityManager.getEMInvocationInfo(JPATxEntityManager.java:191)
[30/10/14 15:18:34:806 CET] 000002a7 SystemErr     R    at com.ibm.ws.jpa.management.JPAEntityManager.createNamedQuery(JPAEntityManager.java:312)
[30/10/14 15:18:38:694 CET] 000002a7 SystemErr     R    at public.PersistableProcessStepStatus.changeFlag(PersistableProcessStepStatus.java:34)
[30/10/14 15:18:38:694 CET] 000002a7 SystemErr     R    at public.PersistableProcessStepStatus.enableDebugMode(PersistableProcessStepStatus.java:51)
[30/10/14 15:18:38:694 CET] 000002a7 SystemErr     R    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[30/10/14 15:18:38:694 CET] 000002a7 SystemErr     R    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
[30/10/14 15:18:38:694 CET] 000002a7 SystemErr     R    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
[30/10/14 15:18:38:694 CET] 000002a7 SystemErr     R    at java.lang.reflect.Method.invoke(Method.java:611)
[30/10/14 15:18:38:694 CET] 000002a7 SystemErr     R    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:69)
[30/10/14 15:18:38:694 CET] 000002a7 SystemErr     R    at sun.reflect.GeneratedMethodAccessor33.invoke(Unknown Source)
[30/10/14 15:18:38:695 CET] 000002a7 SystemErr     R    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
[30/10/14 15:18:38:695 CET] 000002a7 SystemErr     R    at java.lang.reflect.Method.invoke(Method.java:611)
[30/10/14 15:18:38:695 CET] 000002a7 SystemErr     R    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:272)
[30/10/14 15:18:38:695 CET] 000002a7 SystemErr     R    at javax.management.modelmbean.RequiredModelMBean$4.run(RequiredModelMBean.java:1152)
[30/10/14 15:18:38:695 CET] 000002a7 SystemErr     R    at java.security.AccessController.doPrivileged(AccessController.java:298)
[30/10/14 15:18:38:695 CET] 000002a7 SystemErr     R    at com.ibm.oti.security.CheckedAccessControlContext.securityCheck(CheckedAccessControlContext.java:30)
[30/10/14 15:18:38:695 CET] 000002a7 SystemErr     R    at sun.misc.JavaSecurityAccessWrapper.doIntersectionPrivilege(JavaSecurityAccessWrapper.java:41)
[30/10/14 15:18:38:695 CET] 000002a7 SystemErr     R    at javax.management.modelmbean.RequiredModelMBean.invokeMethod(RequiredModelMBean.java:1146)
[30/10/14 15:18:38:695 CET] 000002a7 SystemErr     R    at javax.management.modelmbean.RequiredModelMBean.invoke(RequiredModelMBean.java:999)
[30/10/14 15:18:38:696 CET] 000002a7 SystemErr     R    at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:847)
[30/10/14 15:18:38:696 CET] 000002a7 SystemErr     R    at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:783)
[30/10/14 15:18:38:696 CET] 000002a7 SystemErr     R    at com.ibm.ws.management.AdminServiceImpl$1.run(AdminServiceImpl.java:1335)
[30/10/14 15:18:38:696 CET] 000002a7 SystemErr     R    at com.ibm.ws.security.util.AccessController.doPrivileged(AccessController.java:118)
[30/10/14 15:18:38:696 CET] 000002a7 SystemErr     R    at com.ibm.ws.management.AdminServiceImpl.invoke(AdminServiceImpl.java:1228)
[30/10/14 15:18:38:696 CET] 000002a7 SystemErr     R    at com.ibm.ws.management.remote.AdminServiceForwarder.invoke(AdminServiceForwarder.java:346)
[30/10/14 15:18:38:696 CET] 000002a7 SystemErr     R    at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1466)
[30/10/14 15:18:38:696 CET] 000002a7 SystemErr     R    at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:86)
[30/10/14 15:18:38:696 CET] 000002a7 SystemErr     R    at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1307)
[30/10/14 15:18:38:696 CET] 000002a7 SystemErr     R    at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1399)
[30/10/14 15:18:38:696 CET] 000002a7 SystemErr     R    at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:830)
[30/10/14 15:18:38:697 CET] 000002a7 SystemErr     R    at javax.management.remote.rmi._RMIConnectionImpl_Tie.invoke(_RMIConnectionImpl_Tie.java:751)
[30/10/14 15:18:38:697 CET] 000002a7 SystemErr     R    at javax.management.remote.rmi._RMIConnectionImpl_Tie._invoke(_RMIConnectionImpl_Tie.java:158)
[30/10/14 15:18:38:697 CET] 000002a7 SystemErr     R    at com.ibm.CORBA.iiop.ServerDelegate.dispatchInvokeHandler(ServerDelegate.java:631)
[30/10/14 15:18:38:697 CET] 000002a7 SystemErr     R    at com.ibm.CORBA.iiop.ServerDelegate.dispatch(ServerDelegate.java:501)
[30/10/14 15:18:38:697 CET] 000002a7 SystemErr     R    at com.ibm.rmi.iiop.ORB.process(ORB.java:622)
[30/10/14 15:18:38:697 CET] 000002a7 SystemErr     R    at com.ibm.CORBA.iiop.ORB.process(ORB.java:1581)
[30/10/14 15:18:38:697 CET] 000002a7 SystemErr     R    at com.ibm.rmi.iiop.Connection.doRequestWork(Connection.java:3148)
[30/10/14 15:18:38:697 CET] 000002a7 SystemErr     R    at com.ibm.rmi.iiop.Connection.doWork(Connection.java:3013)
[30/10/14 15:18:38:697 CET] 000002a7 SystemErr     R    at com.ibm.rmi.iiop.WorkUnitImpl.doWork(WorkUnitImpl.java:63)
[30/10/14 15:18:38:697 CET] 000002a7 SystemErr     R    at com.ibm.ejs.oa.pool.PooledThread.run(ThreadPool.java:118)
[30/10/14 15:18:38:698 CET] 000002a7 SystemErr     R    at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1864)

Solution

So the solution to this is:

create persistente-utnit in persistence.xml

    <persistence-unit name="second" transaction-type="RESOURCE_LOCAL">

and change class:

@TransactionManagement(TransactionManagementType.BEAN)
public class PersistableProcessStepStatus extends ProcessStepStatus {
@PersistenceUnit(unitName = "second")
private EntityManagerFactory entityManagerFactory;

private void changeFlag(String namedQuery, String flag, boolean enable) {
    entityManager = entityManagerFactory.createEntityManager();

    entityManager.getTransaction().begin();
    entityManager.createNamedQuery(namedQuery)
            .setParameter("a", prozessName)
            .setParameter("b", vorgangName)
            .setParameter(flag, enable).executeUpdate();
    entityManager.getTransaction().commit();

}