Hi,

I'm trying to create a recursive many-to-many relationship. The entity has a composite id with three columns and uses a single foreign field to refer to itself again. I've been trying several combinations for the last day, but as far as I understand the hibernate documentation, perhaps this can't be done with the current database model. Unfortunately, I can't change the database schema: other legacy applications depend on it.

So, any help / comment would be really welcome (even if it's a "that's not possible", it'd save me spending even more hours on this). As a way to help visualize the relation, imagine a node of a tree. It just has three fields as a composite key (node_id, node_order, node_app) and it uses a single field to link to its children (linked to the next node_id field).

Thanks in advance,

- Juan


Hibernate version: 3.0.5

Mapping documents:

Full stack trace of any exception that occurs:

org.hibernate.MappingException: Foreign key (FK5EAE32D5AA8597E:children [node_id])) must have same number of columns as the referenced primary key (node_tree [node_id,node_order, node_app])[/code]

Well, after spending another whole day on this issue, I think I won't map POJOs to the tables. It seems to me that Hibernate wasn't designed to work with composite keys (and this is something I can't change right now -it's the core of the legacy database model- where there are several many-to-many and one-to-many relationships with composite IDs)

Perhaps the only approach is to use the same plain old SQL I was using before. Anyway, any advise about another approach would be truly welcome.

Regards,

- Juan

This is, of course, utter nonsense and there are many composite key examples in the documentation. Don't come here and insult my product.

AFAICT, Hibernate can easily handle your case. It might require the use of <key property-ref>, I'm not quite sure. Because neither me nor anyone else here can help you since you didn't bother to show what your actual tables look like.

Stop blaming Hibernate for your shortcomings.

Gavin,

Sorry to hear you feel that way. I don’t come here to "insult and blame" your product, it's just the opposite. As far as I can tell in this short space of time, it's excellent -and from many points of view-.

I didn’t find examples about composite IDs like the one I posted above. The examples of this kind are very simple and I was unable to solve the situations like the ones I described with them. As documents I’m mainly using the Hibernate 3 reference doc and your book Hibernate in Action.

Of course all this is a lack of knowledge of Hibernate, and so I’m posting this here. All the common relationships / mappings were done without problems (and working beautifully).

Here are two simplified examples that illustrate the problem. I think that just one example would solve them all.

** Many to many using a composite key **







** Recursive (one-to-many) relationship using a composite key **

[/b]

Use property-ref.

I hope you realize what an incredibly broken data model this is.