我需要将一个类Map到两个表（都有多个列主键）。假设TABLE 1有id 1，id 2，id 3，TABLE 2有id 1，id 2作为主键。现在，在编写Map文件时，我将做如下操作：

<hibernate-mapping package="beans">
  <class name="TABLE1Class" table="TABLE1">
    <composite-id name="table1PK" class="TABLE1PKClass">
        <key-many-to-one name="id1" class="ID1Class" column="id1"/>
        <key-many-to-one name="id2" class="ID2Class" column="id2"/>
        <key-many-to-one name="id3" class="ID3Class" column="id3"/>
    </composite-id>
    <property name="someProperty" type="integer" not-null="true" column="x"/>
    <join table="TABLE2">
        <key column="id1" />
        <!-- <key column="id2"/> The join tag accepts only one key tag!!! 
How do I map the second key??? -->
        <property name="propertyFromTable2" type="float" not-null="true"/>
    </join>
  </class>
</hibernate-mapping>

如您所见，join标记只接受一个key标记！如何Map第二个Id？