Hello,

Here's my scenario: I'm working with a legacy database, where inheritance was implemented using both table-per-class and table-per-subclass schemas. In other words, there's always a discriminator column in "super" tables, even where the hierarchy can be completely recovered using joins.

So, I've decided that the best strategy is to use the table-per-class schema and adopt <join table...> tags to "emulate" table-per-subclass when applicable. Generically:



So far, so good. But...

I've noticed that Hibernate (ver. 3.1 and below) doesn't support <many-to-one> relationships inside joined tables.

1. Why?
   
   (Performance? Postponed feature? Gotchas?)
   
2. How to circumvent this limitation?
   
   My first tought was to implement a class to represent the "extra" data (i.e., the data of the joined table, including collections) and link it to the main entity with one-to-one relationship. To make this transparent, I'd implement getters/setters in the main entity that just redirect calls to extraData.get... and extraData.set... .
   
   However, it seems that I'm adapting my entity model to the persistence layer, which sounds strange at first.
   
   I'd like to hear developers that have faced this situation before...

Also, I see that this is an open issue since nov/04 (Issue #HHH-36), but there hasn't been any comments since then.

Thanks in advance,

I'm deeply sorry: the problem isn't with <many-to-one> tags, but with <one-to-many>, which defines collections.

Weel, the solution couldn't be easier. The <one-to-many> must be outside the <join> element.

This question is over.