Detached entity passed to persist

[jactor]

Hi!

I receive an error when I try to persist an entity bean. I have a bean (A) which relates to another bean (B). This relation is annotated as @ManyToOne(cascade = CascadeType.ALL) and
@JoinColumn(nullable = false)

The enity bean (B) has only one property beside the autogenerated id (Long) which its name (b.getName()). This property is annotated with @Column(nullable = false, unique = true).

I use annotations over the fields of the properties.

When I persist/merge these entities I get

javax.ejb.EJBException: javax.persistence.PersistenceException: org.hibernate.PersistentObjectException: detached entity passed to persist: a.package.B

The methods which tries to persist the entities are:

 public Long saveOrUpdate(A a) {
 B b = a.getB();
 b.setId(saveOrUpdate(b));
 entityManager.flush();

 // If b is persisted before, the persisting gives an exception
 // I have actually never tried the merge option as a.getId() is null...

 if (a.getId() != null) {
 entityManager.merge(a);

 return a.getId();
 }

 entityManager.persist(a);

 return a.getId();
 }

 public Long saveOrUpdate(B b) {
 B persistedB = get(b.getName());

 if (persistedB != null) {
 return persistedB.getId();
 }

 entityManager.persist(b);

 return b.getId();
 }

Since B only have one property (name) and this is unique, my saveOrUpdate method of B only return the id of an allready saved instance. Therefore I use this id on B.setId(Long id) when the method is called.

If B has not been persisted before it works as intended, but if the instance of B is located in the database, then the exception is thrown when I try to persist A... When A is persisted (even though there is a merge option in the code, every time I use this code, I persist a new instance of A - a.getId() == null - which may have an allready persisted instance of B) this exception is thrown even if the correct id is located in the instance of B which is tried to be persisted with A.

Please help me with this exception. I thought a detached entity did not have a valid primary key (b.getId()), but this is not the case in this situation. I am growing frustrated...

[jactor]

Please help me this so I can avoid the big head ache...

After a variety of debugging, this is the case:

 ...
 B b = a.getB();
 long id = saveOrUpdate(b); // Autoboxing. Originally an instance of Long
 entityManager.flush();
 b.setId(id); // Autoboxing. Originally an instance of Long
 ...

I discovered that the memory referance of b.getId() was put to null when I flushed the entity manager. Before the flushing I had done some logging, but it was not valid anymore.

However; after flushing, persisting/merging A, and logging that b.getId() is still a valid value, I still get the same exception:

javax.ejb.EJBException: javax.persistence.PersistenceException: org.hibernate.PersistentObjectException: detached entity passed to persist: a.package.B

Is there some sort of configuration that I did not do? I thought that the merge method would check that the id of the entity was valid.