How straight forward is it to map something like the following sitation?

(another explanation of this exact problem can be found in this thread: http://forum.hibernate.org/viewtopic.php?t=941990 see the post by dtabuenc )

I have 1 Type Hiearchy as follows:

Parent is a super class. Person and Org are joined-subclasses.

This is straightforward and I have mapped this fine.

I also have this super, sub situation as above (joined-subclass):


Again, this part is easy to map. Where I am unsure, is in how I would map a one-to-many where a Person( or any subclass of Party) would have a collection of PostalAddress and a collection of Phone etc.

Parent would connect to Address, Phone through the Contact table. I guess the tricky part is that i want a seperate collection for each Contact subtype not a collection of Contacts. I don't know how to map this so that NHibernate knows it needs to go through the Contact mapping to get the appropriate sub types. How would I go about mapping such a relationship?



Thanks,
Christian[/url]

Is this not possible?

It should be pretty straightforward, just use <set><one-to-many class="Address" /></set> and <set><one-to-many class="Phone" /></set>, etc.

Sergey,

THat doesn't work. I have the following.
(another explanation of this exact problem can be found in this thread: http://forum.hibernate.org/viewtopic.php?t=941990 see the post by dtabuenc )



I captured the query in SQL Server profiler and NHibernate passes the personid value as the contactid. It's missing the join through the Contact table.

Nhibernate needs to create a query like:

Make sense? Am i missing something?

edit: added mapping files

I guess it would be fair to assume this isn't possible?

Hmm, if Gavin says it's not possible in the linked post then the answer has got to be the same for NHibernate...

That's disappointing. I imagine there is a pattern to deal with this situation. Any insights? I might have to ditch NHibernate, which is too bad.

Christian

Be flexible and creative! Hibernate is just a tool, and every tool has limitations! If you can't map the collections easily, you can always build a method in some Dao class which will return the results from a HQL query or even a SQL query. So you can have:



another approach: have a polymorphic collection in your Parent base class of Contact objects. This is straightforward to map. Add methods to your Parent class which return what you want: Address, Phone collections by filtering the existing mapped collection of Contact objects. When the collection filtering from Hibernate 3 will be ported to NHibernate I think will be trivial to do this.

HTH,
radu

THanks radu. I have gone down that path. I am having a problem though. I am attempting to implement it as:



THe mapping looks like this:


I am getting the following error:
"Cannot instantiate abstract class or interface: Demo.Contact"

I am obviously not an expert when it comes to OO stuff :)

Thanks,
Christian

check that for every row in the table which maps the Contact base class there is a corresponding entry in the tables for the derived classes. If there is an "orphan" row in the Contact table this means that hibernate will try to instantiate a Contact object, hence the error.

Radu

Ok, so if i only have say to of the 3 subtypes implemented NHIbernate will do this? There are actually 3 subtypes. I only created 2 as i am protoyping. Will this cause NHibernate to throw this error?

No, it shouldn't. Have you checked the data in your tables? If you have rows in Contact table whithout corresponding rows in one of the already mapped subclasses the error will manifest. For testing purposes you can remove the abstract qualifier from the Contact base class. Don't forget to provide a default constructor even if its private.

Radu

There are no orphaned rows, I just checked. Is there anything else that might cause this?

from hibernate point of view they can be orphaned if you mapped only 2 of the 3 tables. The rows corresponding for the 3rd table are seen as orphans as you didn't map the subclass.

Radu