EJB3 in Action - JTA transaction within a application-managed EntityManager within a container

[Tyronne Fernando]

@Stateless
public class ItemManagerBean implements ItemManager {
@PersistenceUnit private EntityManagerFactory entityManagerFactory;
private EntityManager entityManager;
public ItemManagerBean() {}

@PostConstruct public void initialize() {
entityManager = entityManagerFactory.createEntityManager();
}
...
public Item updateItem(Item item) {
entityManager.joinTransaction();
entityManager.merge(item);
return item;
}
...
@PreDestroy
public void cleanup() {
if (entityManager.isOpen()) {
entityManager.close();
}
}
...
}


The above code is from pages 308 and 309 of "EJB 3 in Action" book. This bean is using an application-managed EntityManager within a container. In the updateItem() method where does the JTA transaction comes from when we call entityManager.joinTransaction()? Is it created by the container?

Thanks in advance.

[Remko Strating]

It's a container managed JTA-Transaction. The transaction isn't created in the code. So it should be created by the containter.

void joinTransaction()

Indicate to the EntityManager that a JTA transaction is active. This method should be called on a JTA application managed EntityManager that was created outside the scope of the active transaction to associate it with the current JTA transaction.