GAE JPA2 OneToMany relationship not detached

Question

I have an issue with my OneToMany relationships in my GAE JPA2 applicaiton.

I have two classes:

@Entity(name="A")
public class A {
    @Id
    private String uuid;
    @OneToMany(mappedBy="a")
    private List<B> bList;

    public A() {
        //set uuid
        bList = new ArrayList<B>();
    }

    public List<B> getBList() {
        return bList;
    }

    //Other getters and setters

    public static A create() {
        EntityManager em = //get entity manager
        A a = new A();
        try {
            em.persist(a);
        } catch(Exception e) {
            return null;
        } finally {
            em.close();
        }

        return a;
    }

    public static A getA(String uuid) {

        EntityManager em = // get EM
        A a = em.find(A.class, uuid);
        em.close();
        return a;
    }

    public void update() {
        EntityManager em = // create EM
        try {
            em.merge(this);
        } finally {
            em.close();
        }
    }
}

@Entity (name="B")
public class B
{
    //id stuff

    @ManyToOne(fetch=FetchType.EAGER)
    A a;

    public B(A a) {
        //create key using 'a' as parent
        this.a = a;
    }

    public static B create(A a) {
        EntityManager em = //create EM
        B b = new B(a);
        try {
          em.persist(b);
        } catch (Exception e) {
          return null;
        } finally {
          em.close();
        }
        return b;
    }

    //get and update methods similar to the A class above

}

And then I have a little testbed service where I am doing the following:

String uuid; //hardcoded to match an existing uuid in the datastore
A a = A.getA(uuid);
B b = B.create(a);
a.getBList().add(b);
a.update();

I am confused as to why the list isn't being detached... I could understand it if my FetchType was LAZY, but it's not... It's set to EAGER.

Any ideas?

UPDATE I can reproduce the problem just as well by only using the following lines in my testbed service

String uuid; //hardcoded to match an existing uuid in the datastore
A a = A.getA(uuid)
a.getBList();

Answer 1

1. Before persisting b, you forgot to add it to the a's list.
2. Another problem could be that you use two different EntityManagers that have nothing in common. Try using the same em when saving A and B.