Hi,

I use Hibernate and everything is fine. I need to know if there is a trivial solution to my probllem.

In an application transaction - session-per-request-with-detached-objects

I have the following scenario.

req1.
Group group = session.get(Group.class, idGroup);
Person person = new Person(idPerson);
group.getPersons().add(person);
session.save(person);
session.save(group);
session.close();
req.getSession().addAttribute("ddd", group);

req2.
Person person = session.get(Person.class, idPerson);
group.getPersons().remove(person);
session.close();

req3.
// here we create a transcient unsaved object with the same ID as
// the ID of the object in the DB but not removed yet - the user
// modifications are not finished yet
Person person = new Person(idPerson);
group.getPersons().add(person);
session.close();

req4.
session.update(group);
// or
session.merge(group);

When we try to save the modifications there is a constraint violation - we attempt to
insert an object that is already stored in the DB. Actually the remove statement is
not executed.

I would agree that this is how hibernate should work but can you tell me a smart way to solve the problem. I am working on the interceptor and will try to tell the hibernate that this is a detached object and only update will be made.

Thank you in advance.

I met the problem in a much more complex situation and I am lookong forward to solve it.

1. Do you call transaction.commit() in your code?
2. Have you specified cascade="all" in group-persons relationship?
3. Does Person class redefines equals() and hashcode() so it really get removed from collection on remove (aPerson)?

Well, everithing about cascades, and etc. is written and made to work just fine.

Actually the code fails in just one case - when I remove the person and then add a new unsaved transcient instance with THE SAME ID.
If I simply remove person, or add a persistent person or add a new unsaved trancient user with ID not stored in the DB everything is fine, fine, fine up to perfect.

The only problem arises when I remove a persistent object from the collection and later on add a new transcient instance with the same ID.
Hibernate checks the version number of the newly added object and finds the unsaved value - in my case negative. Then it tries to insert a new row. But on the previous removal the delete statement is missed because the group is detached and of course not savet - this is application transaction, wrigtht ?