Lets assume I have two tables

Table tA
    ID
    ID2
    SomeColumns
Table tB
   ID
   ID2
   SomeOtherColumns

I am looking to create a Object let's call it ObjectA (based on tA), that will have a one-to-many relationship to ObjectB (based on tB). In my example however, I need to use the combination of ID and ID2 as the foreign key. If I was writing SQL it would look like this:

select tB.* from tA, tB where tA.ID = tB.ID and tA.ID2 = tB.ID2;

I know that for each ID/ID2 combination in tA I should have many rows in tB, therefor I know it's a one-to-many combination. Clearly the below set is not sufficient for such mapping as it only takes one key into account.

<set name="A2" table="A2" generic="true" inverse="true" >
  <key column="ID" />
  <one-to-many class="A2" />
</set>

Thanks!