I am running into a concurrency issue in my JBPM 5.4 application.  At first I thought it was related to thread safety of the StatefulKnowledgeSession issue discussed elsewhere, but I am able to recreate the issue without any session at all.

I am using the Spring JtaTransactionManager with annotated transaction boundaries, with MySQL, and running on AS 7.1.1.

The Spring configuration looks like this:

{code:xml}<jee:jndi-lookup id="emf" jndi-name="persistence/myEmf"/>

<bean id="sel" class="org.drools.SystemEventListenerFactory"


factory-method="getSystemEventListener" />

<bean id="jbpmTaskService" class="org.jbpm.task.service.TaskService"


c:emf-ref="emf" c:systemEventListener-ref="sel" />

<bean id="localTaskService" class="org.jbpm.task.service.local.LocalTaskService"
 


c:taskService-ref="jbpmTaskService" />

<bean id="jpaDialect" class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" />

<bean id="txManager" class="org.springframework.transaction.jta.JtaTransactionManager" />

<tx:annotation-driven transaction-manager="txManager" />{code}
 

And the code triggering the problem is this:

{code}
List<TaskSummary> tasks = localTaskService.getTasksAssignedAsPotentialOwner(assignee, "en-UK"));
       for (TaskSummary summary: tasks){
             // ...
                org.jbpm.task.Task t = localTaskService.getTask(summary.getId());
             // ....
            }
        }
{code}

Note that this code is annotated as @Transactional

If I call this code from a single thread or inside a synchronized block I have no problems.  If I call it from multiple concurrent threads, I consistently trigger the error:

java.lang.IllegalStateException: Trying to return an unknown connection2! org.jboss.jca.adapters.jdbc.jdk6.WrappedConnectionJDK6@2a77a3c4

The trigger seems to be the inner call to the localTaskService.  With just the outer call I have no problems. 

Googling this error, it seems this was a common problem with older hibernate versions (2.x) but I did not find any references to people seeing it for hibernate 4.x.

Any ideas?

Thanks,

Jon