CODEWITHSUNDEEP
javajpa
user2889419
user2889419

Reputation:

JPA, removing an entity which has found by different manager

Assume we have a simple entity bean, like above

@Entity
public class Schemes implements serializable{
...
@Id private long id;
...
}

I find a record using find method and it works perfect, the problem is I cannot manipulate it(remove) by another EntityManager later, for example I find it with a method, and later I want to remove it, what is the problem?! if I find it with same manager again I would remove it, but if object has found by another manager I cannot.

@ManagedBean @SessionScopped class JSFBean {
private Schemes s;
  public JSFBean(){
    ....
    EntityManager em;//.....
    s=em.find(Schemes.class,0x10L);//okay!
    ....
  }

  public void remove(){//later
    ....
    EntityManager em;//.....
    em.getTransaction().begin();
    em.remove(s);//Error! some weird error, it throws IllegalArgumentException!
    em.getTransaction().commit();
    ....
  }
}

many thanks.

Upvotes: 0

Views: 109

Answers (1)

kostja
kostja

Reputation: 61558

You are probably getting a java.lang.IllegalArgumentException: Removing a detached instance.

The two EMs do not share a persistence context and for the second EM, your object is considered detached. Trying to remove a detached object will result in an IllegalArgumentException.

You can refetch the entity before the removal:

Schemes originalS = em.find(Schemes.class, s.getId());
em.remove(originalS);

EDIT You can also delete the entity without fetching it first by using parametrized bulk queries:

DELETE FROM Schemes s WHERE s.id = :id

Be aware that bulk queries can cause problems on their own. First, they bypass the persistence context, meaning that whatever you do with a bulk query will not be reflected by the objects in the persistence context. This is less an issue for delete queries than for update queries. Secondly, if you have defined any cascading rules on your entites - they will be ignored by a bulk query.

Upvotes: 1

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