尝试捕获持久异常

Question

simple problem. Here is the code :

public void insertDefacer(Defacer defacer) {
    try {
        em.persist(defacer);
    } catch (PersistenceException | DatabaseException e) {
        defacer = em.find(Defacer.class, defacer.getIdentity());
        defacer.setStats(defacer.getStats() + 1);
        em.merge(defacer);
    }
}

when defacer already exists in database (mysql), the persist operation throws an Exception ( PersistenceException and/or DatabaseException ). It seems normal. So I want to catch these exceptions and threat them. But after logging these exceptions, my program ends abruptly (without finish the method).

Why ?

Detail (It could be important or not) : em is an EntityManager get through @PersistenceContext

Answer 1

Are you trying this way to get EntityManager?

@PersistenceContext
private EntityManager em;

public EntityManager getEntityManager() {
return em;
}

public void setEntityManager(EntityManager em) {
this.em = em;
}

Answer 2

You should not be using your EntityManager inside the catch clause as it may be in a corrupted state. Exceptions in JPA are not recoverable, so you should assume that your transaction cannot and will not be completed if an Exception happens.

public void insertDefacer(Defacer defacer) {
    EntityTransaction tx = null;
    try {
        tx = em.getTransaction();
        tx.begin();
        em.persist(defacer);
        tx.commit();
    } catch (Exception ex) {
        if(tx != null && tx.isActive()) tx.rollback();
    } finally {
        em.close();
    }
}

Answer 3

I found an alternative. Just see the code :

 @TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
    public void insertDefacer(Defacer defacer) {

   Defacer df = em.find(Defacer.class, defacer.getIdentity());
   if(df == null) {
      em.persist(defacer);
      System.out.println("Save");
   } else {
      em.merge(defacer);
      System.out.println("Update");
   }

}

As I said It's a palliative solution . Thanks for your help.

Answer 4

确保PersistenceExcetion属于休眠包。