How can I commit a Play! JPA transaction manually?

问题:

Usually, Play! commits the transaction after a request completes successfully. What is the correct way to commit a transaction manually in Play?

void addPerson() {
  Person p = new Person("John", "Doe");
  p.save();

  // TODO - commit the transaction

  // Now p should have an ID
  assert p.id != null;
  usePersonIdForSomethingNasty(p.id);
}

回答1:

You can get the Hibernate EntityManager by calling JPA.em(). Then, from there, you have access to the transaction (JPA.em().getTransaction()).

If you intend to manage the transaction yourself, you will want to disable Play!'s transaction handling (there is a @NoTransaction annotation you can use on the method or controller to do that). Otherwise, Play! will try to commit the transaction at the end of the request anyway, and if you have already done that yourself, that will cause an exception.

回答2:

You don't need to do anything. After the request finishes without any exception, the transaction will be commited for you.

Just ensure to call "save" on all entities you want to persist at the end of transaction.