Deleting OneToMany Entities in EJB3

[Mike Litherland]

Hi,

I'm really stuck trying to delete related entities in EJB3. I have a one to many relationship between two tables and I can't figure out how to delete the child entity.

Let's say my primary bean, the parent is using a list collection to hold the child beans

public List<Kids> getKids() {...

I haven't had any luck doing this:

parent.getKids().remove(aKid);

It doesn't seem to actually remove the relationship, even if I do an em.merge(parent) on it. On the other hand if I try to remove the child directly I get exceptions:

em.remove(aKid);

produces:

Caused by: javax.ejb.EJBException: javax.persistence.PersistenceException:
org.hibernate.NonUniqueObjectException: a different object with the same identifier value was
already associated with the session: [org.me.MyClass#452]

So which way is the right way to get rid of the child entity and ensure it's deleted from the database? Is there something I need to do to ensure the object is unique in the session?

Thanks much for the help.
Mike
[ June 26, 2006: Message edited by: Mike Litherland ]

[Mark Spritzler]

What is your cascade setting for your parent table. Does it cascade deletes. I think you would update the parent object after removing the children. Or can you loop through the childs calling the session.delete() and then commit the transaction?

Mark

[Mike Litherland]

Thanks for the reply.

I did find out from browsing through the O'reilly EJB3 book (version 5) that I'm essentially doing things the right way. They recommend "always wire both sides" of a relationship. In this context it's saying do both to delete the object:

parent.getKids().remove(kid);
em.remove(kid);

However, in this case that's when I get this exception. I'm going to ask on the JBoss forums and see if their gurus have any thoughts on what I'm doing wrong.

Thanks again.

[Joe J. Wang]

Only a guess, not sure what is the correct answer, (just started to learn EJB3. )

How about you make the parent bean detached from the EM, (is there any method in em to do this job? clear() will detach all the managed entities), and then do em.remove(akid)? then if you want to use the parent, em.find(parent.class, xxx)...
[ June 27, 2006: Message edited by: Joe J. Wang ]

[Dean Pullen]

I'm having a similar problem.

I do parent.remove(child)
then em.remove(child)


But still get an exception - what is the correct process?