many-to-many without using primary keys

davecasserly · **Joined:** Fri Feb 25, 2005 10:59 am **Posts:** 4

Hibernate version: 3

Hi,

I have a many to many association but i dont want to use the primary key on either object.

Can i do this?

I have a MediaPackGroup which contains a set of MediaPacks

The MediaPackGroup can have a category id and each MediaPack is also given a category.

If this doesnt make sense, i can explain more.

Thanks

tenwit · **Joined:** Thu Dec 23, 2004 9:08 pm **Posts:** 2008

many-to-many supports property-ref.

Assuming that there's a category table, which is your referential-intergrity table (but we'll pretend that it's a join table in this mapping):

Code:

<class name="MediaPackGroup" ...>
  ...
  <set name="Packs" table="Category" ...>
    <key column="categoryid"/>
    <many-to-many column="categoryid" class="MediaPack" property-ref="Groups"/>
  </set>
  ...
</class>

<class name="MediaPack" ...
  ...
  <set name="Groups" table="Category" ...>
    <key column="categoryid"/>
    <many-to-many column="categoryid" class="MediaPackGroup" property-ref="Packs"/>
  </set>
  ...
</class>

You don't need to map the category table if you don't want to. At least one of these tables needs an inverse="true" attribute: from your description, I'd say that both sides should be inverse (so that rows in the category table are never deleted).

I've never tried a mapping like this, where both the parent and child table use the same column in the join table, but I don't see any reason why it shouldn't be possible, if you set inverse="true" on both sides of the mapping.