spring mongodb中去掉_class列

調用mongoTemplate的save方法時, spring-data-mongodb的TypeConverter會自動給document添加一個_class屬性, 值是你保存的類名. 這種設計並沒有什麼壞處. spring-data-mongodb是爲了在把document轉換成Java對象時能夠轉換到具體的子類. 但有時候我們並不希望出現這個字段, 主要是看上去會比較"煩". 可以通過設置MappingMongoConverter的MongoTypeMapper來解決這個問題.

DefaultMongoTypeMapper類的構造函數的第一個參數是Type在MongoDB中名字. 設置爲null的話就不會在保存時自動添加_class屬性.所以需要覆寫 

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>

註解方式：

@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();
    }
}

當使用Servlet 3初始化確保添加應用程序上下文到mongo中，如果不加上這兩句，會報異常：org.springframework.expression.spel.SpelEvaluationException
@Autowired
private ApplicationContext appContext;
mongoMappingContext.setApplicationContext(appContext);