Hi guys,

I'm using latest version of Hibernate

here's what I wanna do and how I figure out I should implement the mapping:

I have a bottom-up approach in my app, this is why i'm starting from the Tables

I want to have a table A that can have a reference to B OR C.
As I don't wan't to use nullable FK, i'm using an association that is composed of (ID_A, TYPE, ID), Type being B or C.

It works fine from a relational point of view.
Now the Hibernate documentation on ternary associations is rather slim... so I need some help on this point!

How shall I best implement the corresponding mapping?
What are the possibilities offered by Hibernate?

What are the possibilities?
- B referenced by A
- C referenced by A
- B and C referenced by A
- neither B nor C referenced by A

It's a mutually exclusive OR:

A can reference B OR C, but neither both nor none

I figured out I probably should be using the <any> attribute. like this:

<any name="BorC" id-type="long" meta-type="class">
<column name="TYPE"/>
<column name="ID"/>
</any>

but the doc specifies "You should use this only in very special cases (eg. audit logs, user session data, etc)." which sound bizarre to me since i've got several cas like that in my CDM.

And I can't understand wht I shall do with meta-type attribute. Example are not meaningful to me.

And then I don't know how to use this in a ternary association, it remains very fuzzy to me whether to use <index-many-to-many> <many-to-many> or <set> or... and how hibernate is gonna behave after that.

what about saying that a is abstract and b and c inherit a ?

Hum, whould have beeb nice, but it's not possible here, it's to very different object (say USER and EXPENSE!)

But I needed this stuff, I carrefully read the Inheritance Mappings chapter and had a successful implementation of table-per-subclass. Amazing! It works so well...

Here I indeed have ... say an EXPENSE that can be related to say a USER or a COMPANY....
I actually have 2 tables. COMPANY_EXP and USER_EXP, but since they contains exactlly the same fields it's not a good design. I could have two nullable FK, but it's not good either.

THe proper way to implement this is really to have this association.
I'm sure some already faced this issue. But I keep not understanding the few sentences in the Ternay Associations Chaprter:

"One approach is to use composite elements (discussed below). Another is to use a Map with an association as its index."
That's really to short for me...