如何使用复合主键为下表结构编写休眠映射

我在为下面的表结构编写休眠映射时遇到困难

Throttle                SAMPLEDATA
-------------          --------------------------------
OBJID  INT(PK)      OBJID | NUM_WHEELS |    NUM_BRAKES
NUM_WHEELS INT         --------------------------------
NUM_BRAKES INT      1234  | 2   |  2
                    1235  | 2   |  2
                    1236  | 2   |  2

NOTCH                   SAMPLEDATA
-------------           ---------------------------------------
THROTTLE_OBJID(PK+FK)INT    THROTTLE_OBJID |POSITION |  SECONDS
POSITION INT(PK)        ---------------------------------------
SECONDS INT         1234  | 1       |  2
                    1234  | 2           |  2
                    1234  | 3       |  2


DYNBRAKE                SAMPLEDATA
-------------           ---------------------------------------
THROTTLE_OBJID(PK+FK)INT    THROTTLE_OBJID |POSITION |  SECONDS
POSITION INT(PK)        ---------------------------------------
SECONDS INT         1235  | 0       |  2
                    1235  | 2       |  2
                    1235  | 4       |  2

NOTCH＆DYNBRAKE表具有组合的主键，作为THROTTLE_OBJID和POSITION的组合。我的要求是，每当我从Throttle表中删除一条记录时，都应删除Notch和DynBrake表中的相应引用。

对于这种数据库结构，我的休眠映射如下。

THROTTLE mapping file
=========================

<hibernate-mapping> 
    <class name="Throttle" table="THROTTLE">

        <id name="objId">
            <generator class="sequence">
                <param name="sequence">throttle-seq</param>
            </generator>
        </id>

        <property name="numWheels" type="int" column="NUM_WHEELS" />
        <property name="numBrakes" type="int" column="NUM_BRAKES" />

        <map name="notch" cascade="all" inverse="true">
            <key column="THROTTLE_OBJID"/>
            <index column="POSITION" type="int"/>
            <one-to-many class="Notch"/>
        </map>  

        <map name="dynbrake" cascade="all" inverse="true">
            <key column="THROTTLE_OBJID"/>
            <index column="POSITION" type="int"/>
            <one-to-many class="DynBrake"/>
        </map>  
    </class>
</hibernate-mapping>

NOTCH mapping file
=========================    

<hibernate-mapping>
    <class name="Notch" table="NOTCH">
        <composite-id name="id" 
            class="Order$Id">
        <key-property name="position" column="POSITION" type="int"/>
        <key-one-to-many name="throttleObjId"/>
        </composite-id>
        <many-to-one name="throttleObjId" class="Throttle" column="THROTTLE_OBJID"/>
        <property name="seconds" type="int" column="SECONDS" />                    

    </class>
</hibernate-mapping>

DYNBRAKE mapping file
=========================
<hibernate-mapping>
    <class name="DynBrake" table="DYNBRAKE">
        <composite-id name="id" 
            class="Order$Id">
        <key-property name="position" column="POSITION" type="int"/>
        <key-one-to-many name="throttleObjId"/>
        </composite-id>
        <many-to-one name="throttleObjId" class="Throttle" column="THROTTLE_OBJID"/>
        <property name="seconds" type="int" column="SECONDS" />                    
    </class>
</hibernate-mapping>

通过这种映射配置，我收到“无法为#Notch初始化集合”的异常。我必须维护Throttle.hbm.xml中的代码，因为在应用程序的其他部分中有大量的代码依赖于此映射。所以我不想在这里将集合映射更改为SET或BAG。

在这方面有人可以帮助我吗？