spring mongodb中去掉_class列

调用mongoTemplate的save方法时, spring-data-mongodb的TypeConverter会自动给document添加一个_class属性, 值是你保存的类名. 这种设计并没有什么坏处. spring-data-mongodb是为了在把document转换成Java对象时能够转换到具体的子类. 但有时候我们并不希望出现这个字段, 主要是看上去会比较"烦". 可以通过设置MappingMongoConverter的MongoTypeMapper来解决这个问题.

DefaultMongoTypeMapper类的构造函数的第一个参数是Type在MongoDB中名字. 设置为null的话就不会在保存时自动添加_class属性.所以需要覆写

spring的配置文件方式:

<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> 

注解方式：

@EnableMongoRepositories(
        basePackages = {"com.dhp"},
        repositoryFactoryBeanClass = DHBMongoRepositoryFactoryBean.class
)
@PropertySource("classpath:mongo.properties")
@EnableMongoAuditing
public class MongoConfig extends AbstractMongoConfiguration {  

    @Value("${mongo.connectionString}")
    private String connectionString;
    @Value("${mongo.dbName}")
    private String dbName;  

    @Autowired
    private ApplicationContext appContext;  

    @Override
    protected String getDatabaseName() {
        return dbName;
    }  

    @Override
    @Bean
    public Mongo mongo() throws Exception {
        MongoClientURI mongoClientURI = new MongoClientURI(connectionString);
        return new MongoClient(mongoClientURI);
    }  

    @Override
    @Bean
    public MongoTemplate mongoTemplate() throws Exception {
        MongoDbFactory factory = mongoDbFactory();  

        MongoMappingContext mongoMappingContext = new MongoMappingContext();
        mongoMappingContext.setApplicationContext(appContext);  

        MappingMongoConverter converter = new MappingMongoConverter(new DefaultDbRefResolver(factory), mongoMappingContext);
        converter.setTypeMapper(new DefaultMongoTypeMapper(null));  

        return new MongoTemplate(factory, converter);
    }  

    @Bean
    public static PropertySourcesPlaceholderConfigurer propertyConfigInDev() {
        return new PropertySourcesPlaceholderConfigurer();
    }
}

当使用Servlet 3初始化确保添加应用程序上下文到mongo中，如果不加上这两句，会报异常：org.springframework.expression.spel.SpelEvaluationException
@Autowired
private ApplicationContext appContext;
mongoMappingContext.setApplicationContext(appContext);