[jboss-user] [EJB 3.0] - 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...

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