Hi,
I am using hibernate 3.0 and
I wonder what is the correct mapping to take advantage of transitive persistence on a many-to-one relationship of two classes pointing on a third.

Basically,
a Person has 1..n address(es)
a company has 1..n address(es)

I'd like to have a single table for all addresses
I am only looking for an uni-directional relationship :
that is : given a person or a company get the adress set...

I've end-up with something like


And in my Java code I take care of storing the correct type and extId... This not elegant, and I am not sure that transitive persistence apply well.

I thing it's a classical case/pattern and I am sure the wisemen you are already have the solution to reach a better mapping.

regards.
TFlop

I now believe that using my 3 tables plus 2 tabls for the joint is the correct mapping (as described in the section 7.3 of ref manual)
Person
Company
Address
PersonAddress
CompanyAddress

Any better mapping ?

add 'cascade="all-delete-orphan"' to the two <set> elements to have hibernate look have transitive persistence for you.

Yes I came to this solution by myself, but what I do not understand is that what I try to achieve is very common I think :
Let me restate the case :


but in the manual point 7.3.3 is said extremly unusual, so I think it must exist a better mapping than unidirectional one-to-one association on a join table

Do Hibernate guys preffer inheritance in this case
a class PersonAddress and anotehr CompanyAddress both extending Address. If so I don't see the point because in my case an address for a person is exactly the same object than an Address for a company.
So here we talk about composition.

What is the recommanded mapping for this pattern ?

I'll give credit for the answer, for sure because I don't want to start going in the wrong way...

I had the exact same situation, and while I got it to map in hibernate it was a huge pain. Unfortunately, I don't have much control over my schema and the way it was mapped out in the DB was to have a CompanyAddress and a PersonAddress tables, but in the code I just wanted to have an Address class.

So I resorted to mapping the class twice using entity-name! Yuck! One for the CompanyAddress table and the other for PersonAddress table. I ended up making it bi-directional, which I could do by mapping it twice, and the Company and Person classes implemented the Addressable interface. I got it to work, but I'm not happy with it. I would be very interested in alternatives.

This seems like such common problem I have to think there is another way.

Thanks
Charlie

For one-to-zero-or-one, I recommend using a many-to-one unique="true". A one-to-one will work, but it's not strictly correct. one-to-zero-or-one is many-to-one unique="true"; one-to-one (strictly speaking) should not allow one-to-zero.

However in your case, I would recommend using polymorphic mapping, union-subclass. Section 9.1.5 of the ref docs explains it. You'll have one Address interface and two impl classes, CompanyAddressImpl and PersonAddressImpl.

Thx for the reply, my mapping use many-to-one unique=true inside a jointable node with optional=true (
<join table="PersonAddress" optional="true">
<key column="personId" unique="true"/>
<many-to-one name="address" column="addressId" not-null="true"/>
</join>) like described in 7.3
which implement a 0..1

If I understand well the mapping you suggest I end up with 2 tables for the two impl classes (PersonAddressImpl and CompanyAddressImpl) instead of my two relation classes...
I must be idiot, but I don't clearly see the pro of your solution.

Mr Chubbard I think my mapping work for you :

the tables in this example are :
person (id, and other column)
company (id, and other columns)
address(id, and other column)
personAddress(idPerson,IdAddress)
companyAddress(idCopany,idAddress)

And I have only 3 classes : person, company and address

If your legacy-you-cannot-touch db schema is like this I do think it will work for you.

regards,

TFlop