Support for Compsite Keys

Excerpt of the email thread on it:
Alejandro Scandroli
to users

Sep 6 (2 days ago)
Hi Ognen

On 9/6/07, Ognen Ivanovski <ognen.ivanovski@netcetera.com.mk> wrote:
> Yes, I/we got this far with the mapping. The question is, will Trails
> handle this?
Sadly it won't be able to do it. I did a quick test and I got :
org.trails.descriptor.IdentifierDescriptor cannot be cast to
org.trails.descriptor.EmbeddedDescriptor

But it should be easy to fix, let me think about it, I will get back to you.

The TRAILS-92_v200709091350 patch includes:

• An ugly hack for making EmbeddedDescriptor work as an IdentifierDescriptor
• An usage example based on the "simple" example.

Notes:

• The EmbeddedId should be Serializable, ergo all its components should be Serializable
• Take a look at AssignedIdAspect.aj to see how to make your POJO implement HasAssignedIdentifier.

Known issues:

• TRAILS-53: The embedded id should never be null.
• (new issue): Associations in the "embeddable id" should never be null or Trails will throw NPEs
• (new issue): NotNull validation annotation does not work for ManyToOne associations in the"embeddable id" (I don't know why), to achieve the same goal you should use the ManyToOne "optional" attribute set to false. So, "optional=false" is MANDATORY.
• (new BAD issue): When a new object repeats an already existing pk, the new object overwrites the old one. I've tried several solutions for this implementing ValidateUniqueAspect like heuristics, but I didn't succeed.

mental note: Use the state information available in HasAssignedIdentifier to avoid overwriting objects when a new object repeats an already existing pk.

it still has some issues with repeated pks, I filed TRAILS-152 to keep track of it.