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Seam Hibernate Serves same EntityManger instance to two separate threads

Answer 1

A:

Well, my first is advice is

If you are using an EJB application, prefer To use a Bean Managed Transaction instead of your custom SeamManualTransaction. When you use a Bean Managed Transaction, you, as a developer, Take care of calling begin and commit. You get this feature by using an UserTransaction component. You can create a Facade layer which begins and commit your Transaction. Something like

/**
  * default scope when using @Stateless session bean is ScopeType.STATELESS
  *
  * So you do not need to declare @Scope(ScopeType.STATELESS) anymore
  *
  * A session bean can not use both BEAN and CONTAINER Transaction management at The same Time
  */
@Stateless
@Name("businessFacade")
@TransactionManagement(TransactionManagerType.BEAN)
public class BusinessFacade implements BusinessFacadeLocal {

    private @Resource TimerService timerService;
    private @Resource UserTransaction userTransaction;
    /**
      * You can use @In of you are using Seam capabilities
      */
    private @PersistenceContext entityManager;

    public void doSomething() {
        try {
            userTransaction.begin();
            userTransaction.setTransactionTimeout(int seconds);

            // business logic goes here

            /**
              * To enable your Timer service, just call
              *
              * timerService.createTimer(15*60*1000, 15*60*1000, <ANY_SERIALIZABLE_INFO_GOES_HERE>);
              */

            userTransaction.commit();
        } catch (Exception e) {
            userTransaction.rollback();
        }
    }

    @Timeout
    public void doTimer(Timer timer) {
        try {
            userTransaction.begin();         

            timer.getInfo();

            // logic goes here

            userTransaction.commit();
        } catch (Exception e) {
            userTransaction.rollback();
        }
    }

}

Let's see UserTransaction.begin method API

Create a new transaction and associate it with the current thread

There is more:

The lifetime of a container-managed persistence context (injected Through @PersistenceContext annotation) corresponds to the scope of a transaction (between begin and commit method call) when using transaction-scoped persistence context

Now Let's see TimerService

It is a container-provided service that allows enterprise beans to be registered for timer callback methods to occur at a specified time, after a specified elapsed time, or after specified intervals. The bean class of an enterprise bean that uses the timer service must provide a timeout callback method. Timers can be created for stateless session beans, message-driven beans

I hope It can be useful To you

Arthur Ronald F D Garcia 2010-07-31 07:02:56

Thanks Arthur. Your post forced me to do one thing, reread my code. In the LoadController.createWorkloadContentRecords() method I found a SeamManualTransaction that is not required due to refactoring. I removed this and my issue now appears to be gone (fingers crossed). However, it does seem odd that the same instance can be injected into two threads while one is till using it.

Scott 2010-08-02 02:06:03

Answer 2

A:

In general, injecting an entityManager in a Seam component of scope APPLICATION is not right. An entity manager is something you create, use and close again, in a scope typically much shorter than APPLICATION scope.

Improve by choosing smaller scopes with a standard entityManager injection, or if you need the APPLICATION scope, inject an EntityManagerFactory instead, and create, use and close the entityManager yourself.

Look in your Seam components.xml to find the name of your EntityManagerFactory compoment.

Paul 2010-08-05 15:42:20

Thanks Paul, I managed to find the root cause of this problem, and yes it was partly due to the use of a EntityManager in the Application scope. I have refactored the code now so that the Orchestrator class does not use a EntityManager at all, but rather the EntityManagers are used within Stateless Session Beans instead.

Scott 2010-08-10 22:02:50

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Seam Hibernate Serves same EntityManger instance to two separate threads

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