How to map the table classes have more than one columns for its primarykey in Hibernate?

[RC]

I have two existed tables, I am NOT allow to altering those tables
The 1st table (tableA) has one column for its primary key, the 2nd
table (tableB) has tow columns for its primary key. I am try to map
these two tables with Hibernate XML. Here are my XML file.

Please see ????? in tow places.

Question 1
1st ???? is <many-to-many> tag in class TableA, but <many-to-many> tag
only allows one column. How do I map it for two columns?

Question 2
2nd ????? is the <key> tag in class TableB, similar that <key> tag only
allows one column. How do I map it for two columns?

Thank Q very much in advance!

<hibernate-mapping auto-import="false"
default-lazy="true" default-access="field">

<class name="tableA" table="TABLEA" entity-name="TableA.class">
<id name="tableAId" type="string" column="TABLEAID"

access="field">
<generator class="native">
<param name="key">TABLEAID</param>
</generator>
</id>
<property name="column1" type="string" column="COLUMN1" />
<property name="column2" type="string" column="COLUMN2" />
.....
<set name="idsa" table="IDS" inverse="true">
<key column="TABLEAID" />
<many-to-many column="????" class="tableB" />
</set>
</class>

<class name="tablesB" table="TABLEB" entity-name="TableB.class">
<composite-id>
<!-- this table's primary key has two columns -->
<key-property name="tableBId1" type="string"
column="TABLEBID1" />
<key-property name="tableBId2" type="integer"
column="TABLEBID2" />
</composite-id>
<property name="column1" type="string" column="COLUMN1" />
<property name="column2" type="string" column="COLUMN2" />
....
<set name="idsb" table="IDS">
<key column="?????" />
<many-to-many column="TABLEAID" class="tableA" />
</set>
</class>
</hibernate-mapping>