I have a unidirectional many-to-one relationship between 2 tables A and B. B can navigate to A and A cannot navigate to B. If I delete A I would like the delete to cascade to B. Is this possible? If so can I get a quick pointer on how?

Regards,
Mike

I've been wondering if this is possible as well. Does anyone have any pointers on how to do this?

If you don't want to map the association from A to B, your only real option is cascading deletes in the database.

That's too bad. So, is this something that would be impossible to add to hibernate or would it be something worthy of an Enhancement request in JIRA? If it is possible it would seem to me very valuable.

Mike

Well, you don't want to define the association, so to what should we attach that metadata?

The metadata would have to be attached to other side in a kind of an inverse-cascade property. I don't have any idea how the internals of Hibernate work but it would obviously require the creation of some sort of listener for the delete of an A objects. Or it would require the session searching for non directly associated relationships with the object.

Again I don't know much about the inner workings of Hibernate so the thought of the session looking for inverse associations is rediculous. :)

Anyway, if it is possible it would be nice.

Mike

How about evicting stale object from caches? Database can't do the all jobs.

Look, its as simple as adding the association to the mapping, and having that association cascade deletes; hibernate will make sure cached stuff gets cleaned-up appropriately.

But if you are unwilling to do that, what is it you want? Should Hibernate some how magically whisk away all your bad decisions? Is it time to start looking at embedding an "intention translator" inside Hibernate? ;)

So, in summary:

1) 'cascading deletes in the database' is not option at all, because this is lead to problems with cache.

2) If I want cascading, then I should add reverse association, which isn't required by object model, but required by Hibernate.

The reason I don't want to add reverse assosiations to my object model is because I don't want to muddle up my object with tons of assosiations it doesn't need to know about. What if I have 10 different object with need to associate with the 1. The object model can get ugly really quick if I always have to add reverse assosiations solely to provide cascading deletes.

I'm not looking for Hibernate to do magic. :) The metadata for the reverse cascade could be stored on the other side of the association. But, based on how you're talking Steve it sounds like it would be impossible for hibernate to untilize this information in that location.....correct? If so then it's not a big deal I'll just have to delete the other objects in my Logic. But it sure would have been nice if hibernate could of done it for me. :)

Mike

Actually I just had a thought Steve. I'm not very good with Hibernate so is it possible to create an association in the mapping file without actually creating a field to associate it to?

If so I can see why you thought it was crazy my not wanting to put the reverse associating in. But if a field would be necissary then my comments and questions remain as stated. :)

Mike

Mike,

I'm in the same situation. I'd rather not bend my domain model to fit hibernate's rules. I've been working on a library to be used with Hibernate that would do cascading deletes of unidirectional associations (including removal of an entity from a collection on an associated entity).

I've requested a sourceforge project to share my work. I'll let you know when it's up.

-Alex

Alex,

Great keep me posted. My project doesn't have a huge requirement for this functionality but it would be nice as long as your solution isn't too invasive.

I tried posting an enhancement but apparently it is "Too hard to implement" for the Hibernate Team.

http://opensource.atlassian.com/project ... se/HHH-266

Mike

You could also always implement this functionality yourself using an Interceptor or Lifecycle, unless thats "too hard for you to implement" ;)

Well the field would have to be there. Typically it'd just be marked as lazy (make it private if you don't want code accessing it). You have to keep in mind that the Hibernate mapping file defines the database schema as much as it defines the object model.