I have a class "A" that has a property of abstract class "B" in a one to one relationship. "A" will have only one "B", but the "B" will change from time to time to different subclasses. Any instantiated "B" subclass will only be related to one "A". "B" does not have a reference to "A".

Please tell me if I'm wrong in thinking that:
1. I cannot map "B" as a component of "A" because it is subclassed.
2. I cannot use a one-to-one with primary key associations without either:
2a. adding a property to "B" to know "A" (impossible in this situation),
or:
2b. having "A"'s id change every time it's "B" changes (very, very inconvenient because I need to refer to objects by their id).
3. I can use a many-to-many from "A" to "B"

I have successfully implemented #3 in my list, but have a second problem when I do. I cannot use cascade="all-delete-orphan" with a many-to-many relationship, so every instantiated "B" object is saved and never deleted. If an "A" goes through 12 different "B"s, all 12 remain in the database despite the object graph only needing one of them.

Does anyone have any suggestions about how I should map this so that I don't have many unnecessary rows in my "B" table?

Thanks for any suggestions,
Scott

Did you try a custom type.

No, I haven't. I considered it, but it looks rather intimidating. Can you point me to some good documentation of how to write one?

Also, in case it influences your suggestion, the example I gave is rather simplified. Real "B"s have six or seven properties that are mostly other objects in my domain. I was under the impression that custom types were for simpler classes like enums?

Thanks a lot for your help,
Scott

I've searched through the online documentation and found no instructions or tutorial for creating complex custom types. Is there information about doing this anywhere?

Anyone have any other ideas?

Try the Wiki community area and the search function on the website with "usertype".

[quote="christian"]Try the Wiki community area and the search function on the website with "usertype".[/quote]

Thank you. I have done that. There are two links to the FAQs that have answers of "Use a UserType." And two links to suggestions for avoiding potential problems with the normal use of UserType. The search returns nothing about CompositeUserType nor how to write a normal UserType.

The API says "A CompositeUserType may be used in almost every way that a component may be used. It may even contain many-to-one associations." Can CompositeUserType, unlike component, handle inheritance?

The searched returns several pages that show you how to implement different usertypes. Try again...

You're absolutely right, there are 15, including the four I mentioned before. Another word or letter must have slipped into the search box before. Sorry for wasting your time with that last post.

I promise to read through these and have at least another cup of coffee before posting again :)

Thanks,
Scott