I am trying to implement the following mapping:
A (1) ----- (*) C
B (1) ----- (*) C

An object of type C may belong either to A or C (not to both). I mapped the foreign key of A and B to the same column on C ("ParentId").

When I tried to export the schema to the database, I got the following exception:

INFO: echoing all SQL to stdout
net.sf.hibernate.MappingException: Repeated column in mapping for class test.C should be mapped with insert="false" update="false": ParentId
at net.sf.hibernate.persister.AbstractEntityPersister.checkColumnDuplication(AbstractEntityPersister.java:720)
at net.sf.hibernate.persister.NormalizedEntityPersister.<init>(NormalizedEntityPersister.java:824)
at net.sf.hibernate.persister.PersisterFactory.create(PersisterFactory.java:32)
at net.sf.hibernate.impl.SessionFactoryImpl.<init>(SessionFactoryImpl.java:207)
at net.sf.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:627)

My question is how to implement this scenario and still have cascade save-update working.

Thank you,

mota

I dont think Databases support that kind of relations
where the same Column is the foriegn key to different tables.

Easiest way is to have an abstract parent class which would implement
all the fucntionality and have two extensions C' and c" and may
a->c' and b->c". this will result in two tables but from the code standpoitn
of view its the same code.

I am trying to implement a scenario similar to the following:

Work object stored in Works table.
Book subclass of Work stored in table Books.
Song subclass of Work stored in table Songs.

Two entities Singer and Author.

Author (1) ---- (*) Book
Singer (1) ---- (*) Song

Works table contains the common field to both Book and Song.

Any idea about the best design practice to handle this scenario.

Thank you,

mota

The other technique u can use is , many to many relation
though its 1->many

A(author)-->(middle table AxW)---> work
S(singer)-->(middle table SxW)-----> work.
Its little more inefficient

Never played with that myself, but you can try the many-to-any tag

Actually it looks like its just a basic <any> mapping.

I came up with the following design:

Author (1) ---------- (*) Book (extends Work)
Singer (1) ---------- (*) Song (extends Work)

I abandoned setting a common foreign key (for both Author and Singer) on the parent class (Work). Instead I moved the foreign keys to subclasses. I have the foreign key of Author in Book, and that of Singer in Song. This way I can keep the one-to-many associations.

Any feedback about this design?

Thank you,

mota

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