JPA不是持久实体

Question

I am trying to save to database changes made to a detached entity. The object of the entity is passed to the function by argument (named as data):

private boolean generate(CommonGameData data) {
        boolean result = true;
        EntityManager em = HibernateUtil.currentEntityManager();
        try {
            em.getTransaction().begin();

            em.merge(data);
            em.flush();
            ...some changes to data object...
            em.persist(data);
            em.flush();
            em.getTransaction().commit();

    } catch (Exception ex) {
        ...
        return false;
    }
        return true;
}

As I have read if I am using the detached entity, I should call merge first. But after commit is done successfully, I don't see any changes in database. Where is the mistake?

Answer 1

As you do not save a new entity (from your comment), you do not need a call to persist() . Also I do not see any reasons to make 'some changes' after calling merge() , so I called merge() after making those changes.

So, try the following:

    em.getTransaction().begin();

    ...some changes to data object...
    em.merge(data);
    em.flush();

    em.getTransaction().commit();

Also very important: if you reuse the EntityManager from the a ThreadLocal variable, you should take care of things like failed past transactions (at least clear it + maybe close it). Also if the bug still persists, try recreating an entityManager.