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[hibernate-dev] Loading data with circular dependencies Cheryl Li Tue Jun 03 06:03:31 2008

Hi all,
I know it doesn't seem to make much sense that there are circular dependencies in a data model, but the requirements make it so. I'm coming across a problem where it becomes a "chicken or the egg" kind of issue...

I will described a scaled-back version of our current model with the following example:
(Obj1: User, Obj2: Specialization)

1) There is a Many to Many relationship between Users and Specializations, because many users can have many specializations. 2) There is a Many to One relationship between Specializations and Users, because each specialization will have a "primary contact" (aka user). This is not nullable either.

Now how does one load the data?
1) Load Users first, but there are ConstraintViolationExceptions since the Specialization objects have not been loaded. 2) Load the Specializations first, but it will complain about the null FK since the User object hasn't been loaded yet.

Right now I am writing a workaround in java where I will load Users first. If a User object breaks the constraint, I will make a clone and load it without the Specializations set (clearing it manually with the setter). But I will keep a list of the failed User objects to load for later. I will load the Specializations second. Then finally, will try to load the "bad apple" Users at the end, with the Specializations set populated. Hibernate should simply update the Users with the Specializations (and thus add records into the M-to-M junction table).

Is there something cleaner I can do to get around these circular dependencies? Something I can leverage in my Hibernate mapping?

Thanks,
-Cheryl
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