spring-data for mongodb save 时多一个_class字段

     spring-data for 与mongodb save 时多一个_class字段，原来的配置文件如下

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
	xmlns:mongo="http://www.springframework.org/schema/data/mongo"
	xsi:schemaLocation="
		http://www.springframework.org/schema/beans 
		http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
		http://www.springframework.org/schema/context 
		http://www.springframework.org/schema/context/spring-context-3.0.xsd
		http://www.springframework.org/schema/data/mongo
		http://www.springframework.org/schema/data/mongo/spring-mongo-1.0.xsd">

	<mongo:mongo id="mongo"  host="192.168.1.2" port="10001" />
	<!-- <mongo:mongo id="mongo" replica-set="127.0.0.1:2222,127.0.0.1:3333"></mongo:mongo> -->
	
	<bean id="userCredentials" class="org.springframework.data.authentication.UserCredentials">
		<constructor-arg name="username" value="his" />
		<constructor-arg name="password" value="his" />
	</bean>

	<bean id="mongoTemplate" class="org.springframework.data.mongodb.core.MongoTemplate">
		<constructor-arg ref="mongo" />
		<constructor-arg name="databaseName" value="his" />
		<constructor-arg ref="userCredentials" />
	</bean>

	<bean id="patcardInfoDao"
		class="com.nbey.data.forward.mongo.business.impl.PatCardInfoDao" />
</beans>

 在实际运行时发现多了一个_class字段，更改如下配置后去除

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
	xmlns:mongo="http://www.springframework.org/schema/data/mongo"
	xsi:schemaLocation="http://www.springframework.org/schema/beans 
		http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
		http://www.springframework.org/schema/context 
		http://www.springframework.org/schema/context/spring-context-3.0.xsd
		http://www.springframework.org/schema/data/mongo
		http://www.springframework.org/schema/data/mongo/spring-mongo-1.0.xsd">

	<mongo:mongo id="mongo" host="172.16.0.126" port="10001" />
	
	<!-- <mongo:mongo id="mongo" replica-set="127.0.0.1:2222,127.0.0.1:3333">
	     <mongo:options             
             slave-ok="${mongo.slaveOk}"   
             write-fsync="true"/>         
	</mongo:mongo> -->

	<bean id="userCredentials" class="org.springframework.data.authentication.UserCredentials">
		<constructor-arg name="username" value="test" />
		<constructor-arg name="password" value="test" />
	</bean>
	
	<bean id="mongoDbFactory" class="org.springframework.data.mongodb.core.SimpleMongoDbFactory">
        <constructor-arg ref="mongo" />
        <constructor-arg name="databaseName" value="test_his" />
        <constructor-arg name="credentials" ref="userCredentials" />
    </bean>
    
	<bean id="mappingContext" class="org.springframework.data.mongodb.core.mapping.MongoMappingContext" />
     
    <bean id="defaultMongoTypeMapper" class="org.springframework.data.mongodb.core.convert.DefaultMongoTypeMapper">  
        <constructor-arg name="typeKey"><null/></constructor-arg>  
     </bean>
     
    <bean id="mappingMongoConverter" class="org.springframework.data.mongodb.core.convert.MappingMongoConverter">  
        <constructor-arg name="mongoDbFactory" ref="mongoDbFactory" />  
        <constructor-arg name="mappingContext" ref="mappingContext" />  
        <property name="typeMapper" ref="defaultMongoTypeMapper" />  
     </bean>  

	<bean id="mongoTemplate" class="org.springframework.data.mongodb.core.MongoTemplate">
	     <constructor-arg name="mongoDbFactory" ref="mongoDbFactory" />  
        <constructor-arg name="mongoConverter" ref="mappingMongoConverter" />  
	</bean>

	<bean id="patcardInfoDao"
		class="com.nbey.data.forward.mongo.business.impl.PatCardInfoDao" />
	
</beans>