Hopefully, this is a simple mapping question.

Class A has a 1-1 unidirectional mapping to Class B, but in the schema I'm working with Table B has the foreign-key mapping back to Table A.

I can't use a one-to-one mapping because I'm not using a shared primary key. Nor can I use a many-to-one mapping with unique="true" and column="fkcol" because the foreign key is on the wrong table.

Theoretically, it should work fine to have the foreign-key on Table B identifying the one-to-one association, but how do I map this? Of course, changing the schema is not an option.