The 'correct' way to instantiate JPA manager bean?

Question

I'm using IBM RAD to develop some JPA entities, and from those, corresponding JPA Manager Beans. Manager beans (which are generated by RAD) have the following member:

@PersistenceUnit
private EntityManagerFactory emf;

I'm not sure how to correclty instantiate (or get a reference to) this manager bean from a stateless EJB (3.0), so I've added a constructor to manager bean where I can pass EntityManagerFactory instance to it. I get a reference to EntityManagerFactory in an EJB by using `@PersistenceUnit' annotation like so:

@PersistenceUnit
private EntityManagerFactory _entityManagerFactory;

This seems rather unnecessary and I believe there must be a way to tell the container (Websphere 7.0 in my case) to 'bootstrap' this for me somehow, so that I get a reference to JPA manager bean right away. Is it?

Update: It seems I haven't bean elaborate enough. Sorry for that.

• There are three objects involved: JPA Entity, JPA Entity Manager and a Stateless EJB.
• JPA Entity Manager class (not an EJB) is created by RAD and has convinience methods (named queries) on it. It also has defined member @PersistenceUnit private EntityManagerFactory emf. I know I can use EntityManager directly, but I'd like to use MyEntityManager for it's convinience methods.
• I can get a reference to EntityManager or EntityManagerFactory in a stateless EJB by using annotations described above (and also like Bozho suggests)
• I would like to get a reference to JPA Entity Manager in a stateless EJB. If I 'new' it up (new MyEntityManager()), the emf field is null. The workaround is to declare @PersistenceUnit field in an EJB and then pass it to JPA Entity Manager and use that.
• Come to think of it, maybe I could declare JPA Entity Manager as an EJB and be done with it... (although this again seems unnecessary). I thought there is a method along the lines PersistenceContext.getJpaManager(MyEntityManager.class) which I am perhaps missing.

Answer 1

@PersistenceContext
private EntityManager em;

It seems you have your custom bean that you want to inject in other beans (it needs a local interface at least):

@EJB
private MyEntityManager em;