Delete

Call EntityManager's remove on a managed entity to DELETE the corresponding row in the database on the next commit.

• The entity becomes detached after the remove and remains available until it is garbage collected.

Actor a = em.find(Actor.class, 1);
em.getTransaction().begin();

em.remove(a); // performs the delete on the managed entity

em.getTransaction().commit();

a.getFirstName();
// a is now a detached entity and does not correspond to a row in the db...
// ... however, it is still an object and can be used as such

Due to the obvious risk of a DELETE, Hibernate can sometimes rollback a transaction behind the scenes. If your em.remove call isn't being committed to the database you can always write a JPQL DELETE statement.

Practice Exercise

In almost all cases you DO NOT want to delete any data from your database. Data is $ in today's world and deleting some would be throwing away valuable information. When Facebook 'deletes' your account, they are actually just deactivating it. All of your info is still permanently stored on there servers.

Drill

1. In your ActorDAO create the following abstract method: public boolean destroy(int id);

   1. Implement the destroy method in your ActorDAOImpl:

   2. Use the provided id to retrieve a managed Actor entity.

   3. Use em.remove to delete the managed entity.

   4. On commit the managed entity will be deleted.

   5. Presuming there is no error and the entity was found, return true, otherwise, return false.

2. To test that your destroy is working, modify ActorDAOTest by commenting out your update, remove the entity you created and modified in the previous two Drills. Check MySQL; the entity should no longer be present in your database.

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