Question

I’m a novice.

Does Jersey and EJB hold the same EntityManager scope?

Should I have to pass the EntityManager to EJB for same persistence context?

The primary target usage is JTA.

@Stateless
class MyEJB {

    public MyEntity find(Long id) {
        ...
    }

    @PersistenceContext;
    EntityManager entityManager;
}


class MyResource {

    @GET
    @Path("/myentity/{id}");
    public MyEntity get(@PathParam("id") final long id) {
        final MyEntity found = myEjb.find(id);
        // is found's state detached?

        // should I have to reattach?
        found.setDate(new Date());

        return found;
    }

    @EJB
    private MyEjb myEjb;

    @PersistenceContext;
    EntityManager entityManager;
}

Answer 1

Does Jersey and EJB hold the same EntityManager scope?

Should I have to pass the EntityManager to EJB for same persistence context?

I don’t think that your wording is correct, but they can share the same EntityManager instance, and you have chosen the right way (through injection). Have a look at this chapter of the Java EE 6 Tutorial:

To obtain an EntityManager instance, inject the entity manager into the application component:

@PersistenceContext
EntityManager em;

So, once again, your approach is correct. With regards to the questions in the code comments: the fact that MyEntity is attached or detached, it depends on the implementation of the find method in your EJB. If you do the following, it will be attached:

public MyEntity find(Long id) {  
    return entityManager.find(MyEntity.class, id);  
}  

Finally, doing this way, if you have chosen JTA to use container managed transactions, the transactions will be automatically bounded with the natural boundaries of MyBean‘s methods. In order to have JTA transactions, you have to use this line in persistence.xml file:

 <persistence-unit name="em" transaction-type="JTA">