Hibernate version:3.1 rc1 (problem also occured in 3.0.5)

Hallo,

after searching through this and the german hibernate forum, I decided to post a question by myself.

I never saw a likewise problem, so I strongly suggest that I've done anything wrong. But I also can't find the point of failure.

Description: A Person(one) has Addresses(many) [in hibernate bidirectionally linked]; if a Person entity is deleted, all regarding adresses will be deleted too (cascade)...so long so good
The thing I want to do is to simply delete an address-entity of a person.
Because of cascading I just don't have to delete the address-entity, but also need to delete the regarding address-objekt from the address-list of person. And that's exactly the problem.



means, adr won't be delete from the Set (confirmed by .size() ), although



May be this has something to do with the implemented equals and hashCode methods?! There were generated by MyEclipse-HibernatePlugin:

(Example Adr)


please help me blowing away the fog of nescience.

Thnx in advance

Btw: Hibernate is impressive

sjtuner,

your problem is exactly as you guessed it. Your hashcode and equals is based on your PK and if that changes, i.e. the object is saved, after you place your objects in a set you will never be able to find it again with remove() or contains() and in fact, add() will produce a 'duplicate'.

Take a look at
http://www.hibernate.org/109.html

I would suspect that your call to remove returns false (there is a boolean returned that you can double check). When adding an object to a HashSet the added object is keyed off it's initial hashcode state. If the key changes you'll never be able to find it normally in a set anymore. Although, the it.remove() should have removed the element IIRC.

I understood your arguments, but what is, if the PK hasn't changed and even the hashCode() method deliveres the same value.
Then that's the case :-(

I know, a very strange case!

So, when you add the object to your set your key is already defined?

No it isn't. As you rightfully guess, at first I add a new address-object to a new person-object and then I persist person to the db.

But I System.out.println'ed all attributes (inkl. PK) of both(adr, adr2) objects to console and both are similar.

The tricky part is that when you add your objects to a set then they are keyed off of the unsaved object's hashcode. Once you save the object and if the hashcode changes then you won't find it in the HashSet.

If you iterate through the set and spit out the hashcodes they WILL match; however, the key is still the old value. But you'll never find it with remove() or contains().

I checked this and you're right!

Thank you very much. I'm going to kind of upgrade my equals and hashCode methods.
At least for the equals method I got something in my mind(compare business keys). Do you have any ideas for the hashCode-Method?

Best regards

...and do you meanwhile have any explanation, why the it.remove() statement doesn't work? (see code in first post)

found an appropriate article :)

Thnx for your help