Hi

Imagine the scenario with standard one-to-one mapping, say Result has one Transaction (and one Transaction can be shared by more Results). Mapping has cascading turned on (cascade="save-update").

Saving (making the object persistent) Result instance cascades saving Transaction.

session.save(result)

But when it comes to saving the result among the same session I get NonUniqueObjectException.

//operation 1
result.setTransaction(sameTransaction);
session.save(result);

//operation 2
result2.setTransaction(sameTransaction);
session.save(result); ->> NonUniqueObjectException - Transaction

This code works properly when both operations are in different sessions.

Any suggestions how to solve it in an ellegant way (that is not: checking if transaction is already in session, then merge it with current transaction, then set merged transaction in result)?

When an object is in persistant state (is associated with a Session object) no other objects that represent the same row can be associated with that Session.

And of course, by saving the "Transaction" entity in the first call, it will be associated with the Session in the second call, causing the exception.

Solution:

use the Session.saveOrUpdate(YourEntityInstance) method. It checks if the entity is associated with the Session and if so performs an update(), rather than a save() on it.

have a look at this part of the docs

http://www.hibernate.org/hib_docs/refer ... g-detached

cheers

Michael

Thank for a quick response, but...

Docs:
http://www.hibernate.org/hib_docs/refer ... g-detached

saveOrUpdate() does the following:
...
if another object associated with the session has the same identifier, throw an exception
...

So obviously I still get this error.

It seems that I can use saveOrUpdateCopy() to shun the NonUniqueObjectException, but this method has been deprecated and replaced by merge(), which in fact works differently ("the given instance does not become associated with the session, it remains detached")

Any ideas?

I have the same problem as following:


I do the following:


Sometimes, not always, statement2 throws org.hibernate.NonUniqueObjectException.

Eargerly want to know how to avoid this.

Thanks in advance.

In your case, NonUniqueObjectException may concern Child or Parent object

Assuming that in both statements parents are different objects (I mean different id, or both id=0, so that hibernate will generate one), perhaps you attach same child to both parents?

And of course NonUniqueObjectException concerns only single transaction. If you consider putting operations on parents (save(parent)) into different transactions, you won't ever get one. Yes, I know that this is not desirable to create more transactions, not mentioning that this is far less intuitive.

Let's wait for some Hibernate gurus. Perhaps they will show us how to avoid NonUniqueObjectExceptions.

Thanks,
Szczepan

I think there are 2 solutions:
- catch NonUniqueObjectException, perform merge(), then save
- separate transactions

Correct?

[quote="szczepiq"]Assuming that in both statements parents are different objects (I mean different id, or both id=0, so that hibernate will generate one), perhaps you attach same child to both parents?

[b]

In my problem, parent in the two statement above is the same object.

I notice in one of the posts above sometimes it happens, sometimes not. Probably you changed a property (field) of the object you saved in the first 'save', that changed your isEqual() outcome.

The ID of the object has not not changed, but the outcome of the isEqual method has. So when the changed object is compared to the one that is in the session, they will have the same ID but are not equal according to the isEqual method, resulting in NonUnique exception.

What you could do is just before the second saveOrUpdate, do an evict of the object in question.

Hope this helps,

Steven

I got this problem on my application aswell.

i changed the cascade type to "merge" in the mapping files.
eg. the hibernate-mapping tag, set default-cascade="merge"

this worked with hibernate 3 mappings.