spring mvc中 mongodbtemplate去除_class无效

 <bean class="org.springframework.context.annotation.CommonAnnotationBeanPostProcessor"/>

    <bean id="mappingContext" class="org.springframework.data.mongodb.core.mapping.MongoMappingContext"/>

    <bean id="dbRefResolver" class="org.springframework.data.mongodb.core.convert.DefaultDbRefResolver">
        <constructor-arg ref="mongoDbFactory"/>
    </bean>

    <bean id="defaultTypeMapper" class="org.springframework.data.mongodb.core.convert.DefaultMongoTypeMapper">
        <constructor-arg index="0" value="null"/>
    </bean>


    <bean id="mappingMongoConverter" class="org.springframework.data.mongodb.core.convert.MappingMongoConverter">
        <constructor-arg ref="dbRefResolver"/>
        <constructor-arg ref="mappingContext"/>
        <property name="typeMapper" ref="defaultTypeMapper"/>
    </bean>

    <mongo:template id="mongoTemplate" db-factory-ref="mongoDbFactory" converter-ref="mappingMongoConverter"
                    write-concern="NORMAL"/>

配置去除_class字段无效 求解？？