Hi alls,
I've got table A and table B.
There's many-to-many relation, But also i need position property of class B, which indicates the object B position in object A collection. The concrete object B has different positions in different A objects.


So i think the best solution is

table A Many-to-many table table B
A ---> | a_id | position | b_id | <--- B
/\
|
concrete position

Java classes:


Is it possible to implement in Hibernate?
Or maybe you have some other ideas how i can implement it?

Thank's

Have a look at http://www.hibernate.org/118.html#A11

It would seem that many-to-many relationships with attributes are mapped using a composite-element combine with a many-to-one. I personally don't find this intuitive.

I'm trying to get a many-to-many working that links back to the same table and also has an attribute on it. The example from the FAQ seems OK but doesn't result in the 2 foreign keys forming a primary key within the link table.

I'd be interested to see your mappings however you end up getting this working.

Hope this helps,


Nick

Thank's
it helped me.

The table structure is org_id(foreign key to organization), category_id(foreign key to category), position(category position in organization)
Here's my mapping config


And here's composite element class

we tried it this way but ran into problems when we wanted to query the link table - it seemed that we couldn't get HQL to return objects that were of the type of our link entity.

After looking at the forums I saw a couple of places were the Hib' team advised making link entities into 1st class one by giving them their own <class> in the mapping files. This has made things easier for use on the HQL side.

Good luck with you project.

Hello all,

I'm also running into this many-to-many with relation details in the relation table. In my scenario, I have:

A<---id_A|id_B|A_B_rel_type--->B<---id_B|id_C|B_C_rel_type--->C



Because I need to capture the rel_type data, I've had to use the composite mapping w/ many-to-one (see above), creating a Relation object for both A--->B and B--->C. However, if I need to get object A, Hibernate runs 1 + (1 * B objects mapped to A) queries, since stating "outer-join" doesn't seem to work with this methodology (as far as I can tell).

Is it possible to get the full "A" object in one query through straight configuration mapping, without resorting to straight SQL or even HQL? Any help would be appreciated...

Thanks!
Jon Aharrah
jon_aharrah@yahoo.com

This is exactly the problem we have (as of yesterday). Jon, did you make any further progress optimizing your mappings to support more efficient HQL querying?