How to map the table cl***** have more than one columns for its primary

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-im****t="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>