Strange @OneToMany generated schema

Question

Hi all,
I just deploy 2 Entities (User and Contact) that are aggregated using a non bijective OneToMany annotation
public class User implements serializable {
@OneToMany(cascade=CascadeType.PERSIST)
private List <Contact> contacts;
And no user field into Contact class (so I can easily serialize User including theirs contacts without circular reference in XML style)
The underlying mysql schema is really strange and is not functional at all, cause not null column reference problem occur when I try to create a new Contact.
I expect to have a contact table with a foreign key user_id field that could be null (a contact can exist without user), but the Toplink essential generate a contact table with an User_ID and a contacts_ID fields, and this fields cannot be null and act as primary key of this table ....
And so when creating a new Contact, a problem occur when inserting a null value for user_id (and contacts_id).
My environment :
IDE :
- Product Version: NetBeans IDE 6.0 (Build 200711261600)
- Java: 1.5.0_13; Java HotSpot(TM) Client VM 1.5.0_13-121
- Glasshfish v2ur1
- Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))
I've created a complete Test suite project where I had reproduce this behaviour (excluding all my other stuff around to spot this point)
So my question is : how to generate a correct DB Schema and not this buggy one ? Is there something that I misunderstand ?
And last : how can I influence Toplink to make the correct thing ? I didn't find any annotation to fine grain schema strategy adjustments.
Any help will be welcome ;)
update information :
I try with postgresql 8.2 instead of mysql ... and I'got the same strange schema.
I try a new project from scratch and same thing ...
I deploy with Hibernate 3 instead of Toplink and this time generated schema is more usable (but not efficient as it could be using normal rdbms modeling rules)
So Toplink seem to be the accused in my problem.. I'll submit this problem to Oracle part and keep Hibernate running ;)
Edited by: AymericB on Apr 3, 2008 6:27 AM

Answer 1

Hello,
It looks you have a unidirectional 1:M between User and Contact. Because you don't have a ManyToOne back pointer from Contact to User, the OneToMany is essentially the same as a ManyTomany in that it requires a relation table. So I believe what you are seeing is a User_Contact relation table that will have User_id and contact_id fields, but nothing else. I think you should be seeing 3 tables - 2 for the entities and 1 for the relation table, and cannot explain why you would have problems inserting new Contacts without more information, but I would suspect something else might be going wrong.
If you want Contact to have a foreign key to User, you will need to have a ManyToOne reference to user, then have the OneToMany specify it is mapped by the ManyToOne attribute.
@ManyToOne
private User user;
@OneToMany(mappedBy="user", cascade=CascadeType.PERSIST)
private List <Contact> contacts
Best Regards,
Chris