Question

I have an entity A with 2 OneToOne relations on a second entity B.

entity   --  @OneToOne(cascade=CascadeType.PERSIST)  -->  entity
   A     --  @OneToOne(cascade=CascadeType.PERSIST)  -->     B

I want to manage the persistence from my entity A.

But when I call em.persist(o) hibernate throws the exception :

org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: [EntityB#null]

As my entities are not persisted yet, their id are nulls. The equals and hashcode of EntityB are not called.

Answer 1

You need to do something to assign an id value to the B. Normally, you’d use @GeneratedValue to do that.