Re: Hibernate M:M mapping plus extra data in intermediary table

Spendius wrote:
When your middle table (that which relates your 2 tables
through a many-to-many relationship) contains more than
the A_ID and B_ID columns but also -for ex.- DATE columns
etc.- is there a way to deal with this extra info with some
more config in your .hbm.xml files or do you really need a
supplementary class to handle this data ?

When you have no more than the 2 ID columns to deal with,
the following mappings are enough:
<set name="events" table="PERSON_EVENT">
<key column="PERSON_ID"/>
<many-to-many column="EVENT_ID" class="Event"/>
</set>
in a file and
<set name="participants" table="PERSON_EVENT" inverse="true">
<key column="EVENT_ID"/>
<many-to-many column="PERSON_ID" class="Person"/>
</set>
in the other .hbm.xml file... And no specific class for the
PERSON_EVENT database table is required - but when this
table contains other columns, is there no way but to create
another class to play with this extra columns ?

If you don't wrap the extra attributes in a class, how would you be able to manage them?
If a many-to-many relationship has extra attributes, this generally means that the relationship entries are entities in their own right.

Now I guess that one could come up with some schema to avoid the definition of an extra class, but I can't imagine that this would be easier to deal with.

Kind regards,
Axel Hallez
.