I am sure there is a simple answer to this that I am missing... I cannot seem to figure out how to map a collection of Addresses to other entities. I am working with a legacy database and am bound by the existing structures. My AddressBook table stores multiple addresses for other entities in my database. The table structures include an address_id field on the other entities. That field is 1 part of a composite id on the ADDRESS_BOOK table, the other part being sequence_number (just an incrementing number unique within each address_id). This allows a join between the two tables on address_id to result in a list of addresses for the entity. I have tried various combinations of lists, maps, sets and idbags on my other entities, but none seem to result in the correct table structure when I let NHibernate create a test DB. Is there any way I can map this collection of Addresses to the User and Organization objects???

Table structures look like this:

ADDRESS_BOOK
id --- PK
sequenceNumber --- PK

USER
id --- PK
address_id

ORGANIZATION
id --- PK
address_id


Classes are:

Address
AddressId (Class that has Id and SequenceNumber properties)

User
Id

Organization
Id


mapping files:

<class name="Address" table="ADDRESS_BOOK">
<composite-id name="id" class="AddressId" access="field">
<key-property name="id" type="Int32" length="8" access="field" />
<key-property name="sequenceNumber" type="Int32" length="3" access="field" />
</composite-id>
<properties......... />
</class>

<class name="User" table="USER">
<id name="id" type="Int32" length="8" unsaved-value="0" access="field">
<generator class="native" />
</id>
<??? SOME COLLECTION OF ADDRESSES HERE ???>
<properties......... />
</class>

<class name="Organization" table="ORGANIZATION">
<id name="id" type="Int32" length="8" unsaved-value="0" access="field">
<generator class="native" />
</id>
<??? SOME COLLECTION OF ADDRESSES HERE ???>
<properties......... />
</class>


Sample data:
ADDRESS_BOOK:
id sequence_number
10 1
10 2
10 3
10 4
11 1
12 1
12 2

USER
id address_id
1 10

ORGANIZATION
id address_id
1 11
2 12

Does address_id have a unique value for each address in the AddressBook table? If so, you should just ignore the sequence_number field and pretend that address_id is the primary key (<id>).

If several addresses share the same address_id, you should use sequence_number as the primary key (<id>), map address_id to a separate property in Address class, and use property-ref attribute when mapping relations to Address in other classes.

Hope that helps...

Sergey, thanks for your reply. I thought my account settings would email me when there was one, so I did not check till tonight.

address_id is not unique for each address in the AddressBook table. Each unique address_id essentially signifies a "group" of addresses that are further distinguished by their sequence_number. the address_id and sequence_number together make up a composite PK.

I will look into your property-ref attribute suggestion. thank you!