Michał Mański [https://community.jboss.org/people/mmanski] created the discussion "Re: Session and thread safety" To view the discussion, visit: https://community.jboss.org/message/762354#762354 -------------------------------------------------------------- Hi, I use JBPM 5.3.0.Final in my project. My application uses EJB 3.1/JPA 2.0 and runs on JBoss 7.1.1.Final. I have similar problem with thread safety. When I use one session for whole application, strange exceptions are thrown (e.g. "javax.persistence.PersistenceException: error during managed flush ... caused by: org.hibernate.AssertionFailure: collection [null] was not processed by flush()", "javax.persistence.PersistenceException: error during managed flush ... Caused by: java.util.ConcurrentModificationException" or "org.hibernate.HibernateException: Found two representations of same collection: org.jbpm.persistence.processinstance.ProcessInstanceInfo.eventTypes") if many users use the application simultaneously. I tried to use the ProcessPersistenceContextManager presented by Sebastian, but it didn't resolve the problem - errors still appear. When I try to user another solution and create new session for every request, I don't know how to dispose sessions. I read in documentation that this method must always be called after finishing using the session, or the engine will not free the memory used by the session. However, I don't know how to correctly dispose a session. If I try to dispose session before end of transaction, an exception is thrown during committing transaction: "javax.persistence.PersistenceException: error during managed flush ... Caused by: java.lang.IllegalStateException: Illegal method call. This session was previously disposed". On the other hand, if i dispose session after transaction commits, another exception is thrown: "Could not commit session: javax.persistence.TransactionRequiredException: No active JTA transaction on joinTransaction call". Does anyone know what is the correct way to dispose a session? -------------------------------------------------------------- Reply to this message by going to Community [https://community.jboss.org/message/762354#762354] Start a new discussion in jBPM at Community [https://community.jboss.org/choose-container!input.jspa?contentType=1&...]