Enthuware

Posted: **Thu Mar 23, 2017 3:49 am**

Paul, thank you for your answer and for clarifying things.

I think that code used in the question is incorrect.

I tried to develop example similar to the one in the question, so I created two stateless beans:

Code: Select all

@Stateless
public class MyStateless {

    @PersistenceContext
    private EntityManager em;

    @EJB
    private MyService myService;

    public void createAndRemoveAddress() {
        Address address = new Address();
        address.setCity("Warszawa");
        em.persist(address);
        em.flush();
        myService.removeAddress(address);
    }
}

Code: Select all


@Stateless
public class MyService {

    @PersistenceUnit
    private EntityManagerFactory emf;

    @TransactionAttribute(value = TransactionAttributeType.MANDATORY)
    public void removeAddress(Address address) {
        EntityManager entityManager = emf.createEntityManager();
        entityManager.remove(address);
    }
}

As you see the semantics of MyService.removeAddress are pretty the same as in the question.

When I called MyStateless.createAndRemoveAddress() in client code I got IllegalStateEception:

Caused by: java.lang.IllegalArgumentException: Removing a detached instance model.Address#0

despite that there is no call to detach() and transaction still proceed.

My conclusion (from this experiment and from our discussion) is that application-managed entity manager has completely different persistent context from the transaction-scoped persistent context created before in JTA transaction, so even if there is an entity managed by the container-managed persistent context, it is seen as detached from the perspective of application-managed entity manager. So I think you should reformulate the example to not to use the app-managed persistent context.

There is no case when removeStudent() will correctly remove managed Student entity.

Posted: **Thu Mar 23, 2017 6:34 am**

What if another method in the same bean creates an EntityManager using emf.createEntityManager() and loads an entity, and then calls removeStudent method?

Posted: **Thu Mar 23, 2017 7:45 am**

I added the following method to MyStateless bean:

Code: Select all

@Stateless
public class MyStateless {
    ...
    public void createAndRemoveAddressByAppManagedEM() {
        EntityManager em = emf.createEntityManager();

        Address address = new Address();
        address.setCity("Warszawa");
        em.persist(address);
        em.flush();

        myService.removeAddress(address);
    }
}

I've got the same IllegalArgumentException after calling createAndRemoveAddressByAppManagedEM():

Caused by: java.lang.IllegalArgumentException: Removing a detached instance model.Address#0

Posted: **Thu Mar 23, 2017 8:24 am**

You are right. Also noticed the following statement in Section 7.7: "An extended persistence context obtained from the application-managed entity manager is a stand-alone persistence context—it is not propagated with the transaction."

Paul.

Enthuware

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