hibernate 联合主键类无法批量保存到数据库的问题

昨天使用hibernate循环批量保存一个联合主键类报出如下错误：
AbstractFlushingEventListener[line:301}: Could not synchronize database state with session
Could not execute JDBC batch update

联合主键类配置如下：
<hibernate-mapping>
    <class name="com.vcmchina.credithour.model.SzGcEvaResult" table="sz_gc_eva_result" >
        <composite-id name="id" class="com.vcmchina.credithour.model.SzGcEvaResultId">
            <key-property name="stuNo" type="java.lang.String">
                <column name="stu_no" length="20" />
            </key-property>
            <key-property name="projectCode" type="java.lang.String">
                <column name="project_code" length="20" />
            </key-property>
            <key-property name="weekNo" type="java.lang.Integer">
                <column name="week_no" />
            </key-property>
            <key-property name="syCode" type="java.lang.String">
                <column name="sy_code" length="20" />
            </key-property>
            <key-property name="semSection" type="java.lang.String">
                <column name="sem_section" length="10" />
            </key-property>
            <key-property name="suNo" type="java.lang.String">
                <column name="su_no" length="20" />
            </key-property>
            <key-property name="semNo" type="java.lang.String">
                <column name="sem_no" length="20" />
            </key-property>
        </composite-id>
        <property name="secType" type="java.lang.String">
            <column name="sec_type" length="10" not-null="true" />
        </property>
        <property name="graType" type="java.lang.String">
            <column name="gra_type" length="10" not-null="true" />
        </property>
        <property name="semFlag" type="java.lang.String">
            <column name="sem_flag" length="10" not-null="true" />
        </property>
        <property name="evaScore" type="java.lang.Integer">
            <column name="eva_score" not-null="true" />
        </property>
        <property name="recordData" type="java.lang.String">
            <column name="record_data" length="30" not-null="true" />
        </property>
        <property name="empName" type="java.lang.String">
            <column name="emp_name" length="50" not-null="true" />
        </property>
    </class>
</hibernate-mapping>

////////////////////////////////////////////////

开始采用的是
public void addSzGcEvaResult(SzGcEvaResult evaResult) {
// TODO Auto-generated method stub
this.getHibernateTemplate().save(evaResult);
}

后来改用merge方法就没有问题了：
public void addSzGcEvaResult(SzGcEvaResult evaResult) {
// TODO Auto-generated method stub
this.getHibernateTemplate().merge(evaResult);
}

我感觉是对象状态的问题，因为我给对象实例化了联合主键，hibernate 认为它不再是瞬态，而是托管状态。
save() --瞬态状态调用,状态变为持久(POJO)
merge()--脱管状态时候调用，状态不变