删除集合中的_class列

默认情况下，Spring Data的MappingMongoConverter为MongoDb中的每个对象添加了一个额外的_class列。例如：

public class User {

    String username;
    String password;

    //...getters and setters
}

保存：

MongoOperations mongoOperation = (MongoOperations)ctx.getBean("mongoTemplate");
User user = new User("mkyong", "password123");
mongoOperation.save(user, "users");

结果：

> db.users.find()
{
    "_class" : "com.mkyong.user.User",
    "_id" : ObjectId("5050aef830041f24ff2bd16e"),
    "password" : "new password", "username" : "mkyong"
}

Spring Data创建了额外的_class列。为了删除额外的_class列，重写MappingMongoConverter，传入new DefaultMongoTypeMapper(null)。

下面介绍了两种删除_class的方法：注解和xml。

1. 注解

@Configuration
public class SpringMongoConfig {

  @Bean
  public MongoDbFactory mongoDbFactory() throws Exception {
    return new SimpleMongoDbFactory(new Mongo(), "database");
  }

  @Bean
  public MongoTemplate mongoTemplate() throws Exception {

    //remove _class
    MappingMongoConverter converter =
        new MappingMongoConverter(mongoDbFactory(), new MongoMappingContext());
    converter.setTypeMapper(new DefaultMongoTypeMapper(null));

    MongoTemplate mongoTemplate = new MongoTemplate(mongoDbFactory(), converter);

    return mongoTemplate;
  }

}

2. XML

<mongo:mongo host="localhost" port="27017" />
<mongo:db-factory dbname="database" />

 <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>

3. Spring Boot

@Bean
public MongoTemplate mongoTemplate(MongoDbFactory mongoDbFactory, MongoMappingContext context) {

    MappingMongoConverter converter = new MappingMongoConverter(new DefaultDbRefResolver(mongoDbFactory), context);
    converter.setTypeMapper(new DefaultMongoTypeMapper(null));

    MongoTemplate mongoTemplate = new MongoTemplate(mongoDbFactory, converter);

    return mongoTemplate;

}

4. 测试

_class已经被删除了。

> db.users.find()
{
    "_id" : ObjectId("random code"),
    "password" : "new password", "username" : "mkyong"
}