Mapping 1:2 won't work in reverse

Question

Hi.
I have another problem with reverse mapping :)
I'm trying to reverse map a table with two
foreign keys to another table.
Table descriptions
Association <<table>
id number primary key
id_role_1 number
id_role_2 number
Role <<table>>
id number primary key
Mapping association to roles works fine,
but mapping from role to association won't work.
Error messages being:
1) The table [ASSOCIATION] is not present in this descriptor.
2) A non-read-only mapping must be defined for the sequence number field.
The same error messages comes when mapping just one of the
foreign keys from role to association.
Any help with this would be appreciated.
- Toni
ps. We have a superclass for Role class, that tries both
association FKs to find out which has a association behind
it (Role is only in one of the association and only one of
the id-fields). Better approach to this also would be appreciated ;)

Answer 1

Toni,
I am a little confused but will answer what I can.
First off any relationship from Role to Association must be accomplished with a Target Foreign Key (TFK) since there is no actual FK field on Role. TFK is an optional check box when you are setting up the table reference.
The tricky part in this relationship is that you really want to ask the database for an Association where id_role_1 or id_role_2 is equal to the ID of the Role in question. To keep with the same schema you may want to setup the TFK 1:1 to one of the FK columns on Association and then customize the query TopLink uses to do the OR condition. This would assume that you NEVER have an Association that can point to the same Role twice. Additionally you will want to write you application code such that it maintains the bi-directional relationship correctly.
Doug