Parent/Child - Delete Node But don't include descendants

fdelisle · **Posted:** Fri Aug 13, 2004 12:29 pm

Hi,

Is it possible to remove a node from a hierarchy of entities (parent/child relation) without remove its descendants node?.

If he decides to include descendants (so remove the whole branch), cascade="all-delete-orphan" is perfect (my mappings are OK, no reason to post them here)

A->B->C

If B is removed [A.removeChild( B );], cascading removes C

However, if the user deletes a node but don't want to include descendants, I thought I could do:

A.removeChild( B );
A.addChild( C );

But it doesn't work.

I'm currently tracing the Hibernate code/log to see what is the problem.

Let me know if you have any idea how I can do this.

kantorn · **Posted:** Fri Aug 13, 2004 12:52 pm

Hi.

Tried mapping something like cascade="save-update" or cascade="none" between B and C?

/C

fdelisle · **Posted:** Fri Aug 13, 2004 12:52 pm

When I try to remove B in

A->B->C without including descendants (C), by doing

A.removeChild( B );
A.addChild( C );

when the commit occurs:

B and C are deleted (cascade)

Throw when trying to add B to A:

Caused by: net.sf.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect) for com.convera.repository.model.gurl.LexicalSetPredicate instance with identifier: 1071

Which is comprehensible.

So, why is C deleted from the DB even if it is not really an orphan (associated to a new parent) ?

Thank you. I really need this to work. If I have to do things manually, just tell me!

fdelisle · **Posted:** Fri Aug 13, 2004 12:56 pm

kantorn

That would probably work, but I would lose the fact I can delete a whole branch by having cascading in action.

That would also mean I would have to delete my object manually (session.delete( object )) since orphans will not be automatically deleted by hibernate (when using the all-delete-orphan cascade style).

But If I have to do things manually, I will. But as written in my previous post, I don't understand why the deleted child entity is considered an orphan since it is now associated to a new parent (and this before the actual commit!)

kantorn · **Posted:** Sat Aug 14, 2004 1:32 am

I think this behaviour makes sense, really. StaleObjectException has to mean that Hibernate has "marked" C for deletion or something like that, and after that it's not possible to handle it without exceptions. We'll just have to accept this, and there probably is a good reason for it.

Wouldn

fdelisle · **Posted:** Mon Aug 16, 2004 4:20 am

Hey,

Yes cloning would work, but that means hibernate will have to delete and reinsert C and all its descendants.

I found a solution!

For A->B->C, suppose you delete B:

Code:

[begin transaction]

// optimization, if we know theres no descendants, we dont have to flush and refresh
if ( B.getChildCount() > 0 ) {
      
    for each child of B {

        A.add( child );

    }

    /* the flush will update all children of C to now point to A (update instead of insert since the entities are already persistent) */
    session.flush();

    // we refresh B since it dont have children anymore
    session.refresh( B );

    // we can now remove B, it has no more descendants
    A.removeChild( B );

[commit transaction]
}

The in-memory domain model, the persistence store and the hibernate cache are all synchronized and reflects what is wanted:

A->C

The only problem is that I can't put this piece of code in the domain entity. Even if that's domain logic, since I access hibernate (the persistence layer). I would be coupling the domain model (pojos) with the persitence layer. So I created a command that take care of this.