Why EclipseLink 's auto commit doesn't work with MySQL? - mysql

Question

Using the following code:
EntityManager manager = factory.createEntityManager();
manager.setFlushMode(FlushModeType.AUTO);
PhysicalCard card = new PhysicalCard();
card.setIdentifier("012345ABCDEF");
card.setStatus(CardStatusEnum.Assigned);
manager.persist(card);
manager.close();
when code runs to this line, the "card" record does not appear in the database. However, if using the FlushModeType.COMMIT, and using transaction like this:
EntityManager manager = factory.createEntityManager();
manager.setFlushMode(FlushModeType.COMMIT);
manager.getTransaction().begin();
PhysicalCard card = new PhysicalCard();
card.setIdentifier("012345ABCDEF");
card.setStatus(CardStatusEnum.Assigned);
manager.persist(card);
manager.getTransaction().commit();
manager.close();
it works fine. From the eclipselink's log i can see the previous code doesn't issue an INSERT statement while the second code does.
Do I miss something here? I'm using EclipseLink 2.3 and mysql connection/J 5.1

Answer 1

I am assuming that you are using EclipseLink in a Java SE application, or in a Java EE application but with an application managed EntityManager instead of a container managed EntityManager.
In both scenarios, all updates made to the persistence context are flushed only when the transaction associated with the EntityManager commits (using EntityTransaction.commit), or when the EntityManager's persistence context is flushed (using EntityManager.flush). This is the reason why the second code snippet issues the INSERT as it invokes the EntityTransaction's begin and commit methods, while the first doesn't; an invocation of em.persist does not issue an INSERT.
As far as FlushModeType values are concerned, the API documentation states the following:
COMMIT
public static final FlushModeType COMMIT
Flushing to occur at transaction commit. The provider may flush at
other times, but is not required to.
AUTO
public static final FlushModeType AUTO
(Default) Flushing to occur at query execution.
Since, queries haven't been executed in the first case case, no flushing i.e. no INSERT statements corresponding to the persistence of the PhysicalCard entity will be issued. It is the explicit commit of the EntityTransaction in the second, that is resulting in the INSERT statement being issued.