Under some circumstance(not all the time) following methond throws NonUniqueObjectException



while the following method never throws NonUniqueObjectException

First question: what is the difference between querying using Criteria and loading using session.get()?

Second question: what should I do if I have to load object with composite identifier?

In following method I can not replace query by get.



NOTE: I'm using Hibernate 2.1.8

Is this problem appears in latest Hibernate version?

There are number of post concerning this toping in the forum (just use Search to see the number) but there was no single worth-while advice...
Unfortunately it seems to be a taboo topic for Hibernate team (even 'Hibernate in Action' does not mention NonUniqueObjectException situations, just state session-level cache uniqueness).
Very sad....

I have similar situation with reasigning detached objects to a session.
Have to bend my logic to overcome this Hibernate restriction and use saveOrUpdateCopy instead of saveOrUpdate

Of course this also an FAQ: http://www.hibernate.org/?cmd=srchdoc&q ... tException

Thank you, Christian, for reply!
But the thing is -- I do not know beforehand, is my object already associated
The object can be associated by another object by association, or can be not
I just do not know.

as for saveOrUpdateCopy -- it just brake logic.
I pass object from higher layer to persistance one and reassociate it.
And use it in logic again...
I do not want to use another instance insted of passed one in logic layer.

So do what the documentation says. Reattach before you do anything else. This is really a simple problem with simple solutions. The original poster has a different problem, but nobody can guess what it could be, because he ignored http://www.hibernate.org/ForumMailingli ... AskForHelp

I'd realy like to do it right! but consider situation.
Have two persistent classes: container and component.
with bidirectional association (lazy or not -- does not matter).

attached container first -- component association will fail if component is associated w container.
and vice versa.

ok, i can check container for component before component association... but if association is deep (container contains another container, contains another,...., contains component)? traverse all possible associations?

Last response: "the first thing is reattachment". Open a Session, reattach your detached graph, no exception.

Christian, I'm deeply appologies, but I did not get you
1) Attach graph
2) Attach component (which is in graph)
3) no NonUniqueObjectException???
This is the way? And all this with Hibernate 2.1?

are you sure you read the question to the end?

hmm. I just checked your idea with hibernate 3.1 -- it throws NonUniqueObjectException as well

I can suggest try to AVOID Non composite relations via collections i.e. if you have Container and Item classes and Item can exist without Container or can present in more than ONE container.
DO NOT make collection of items in Container and DO NOT make collection of containers in Item class. Instead you'll have to create third class and hold realation information in it.

Relations via collections work well only if you have composite relation between classes.
i.e. Class Container contains collection of Item and item can be accesses only my via containers methods and can't exists without Container.

PS I can't understand hibernate developers position ignoring posting.
IMHO ignoring the posts won't solve any problem.

Yes. I think you are right. It's hard to model aggregation relations between domain object.
Unfortunately this restriction imposes serious restrictions on persistent model, you have to develop "hibernate-specific" model.

Is this you personal opinion or these restrictions were described in hibernate documentation?

The FAQ points out one possible solution, but does not really talk about what causes the exception. Is there a code example that shows what might cause this to happen?

I'm getting this exception at the end of my transaction when I call transaction.commit(), no idea why.

when i get this issue and the cause is not obvious and therefore not tidy to fix, i do the following:

1. make sure you have the session's version of the object
- i have a utility method 'reAquire' which basically does the following:


2. make necissary changes to object

3. update() or saveOrUpdate() as necissary

I haven't found a case where this doesn't work yet.