import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.mongodb.MongoDatabaseFactory;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.data.mongodb.core.convert.DbRefResolver;
import org.springframework.data.mongodb.core.convert.DefaultDbRefResolver;
import org.springframework.data.mongodb.core.convert.DefaultMongoTypeMapper;
import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
import org.springframework.data.mongodb.core.mapping.MongoMappingContext;

/**
 * mongo配置文件
 */
@Configuration
public class MongoConfig {

    @Bean(name = "mongoTemplate")
    public MongoTemplate mongoTemplate(MongoDatabaseFactory mongoDatabaseFactory,MongoMappingContext mongoMappingContext) {
        DbRefResolver dbRefResolver = new DefaultDbRefResolver(mongoDatabaseFactory);
        MappingMongoConverter mappingConverter = new MappingMongoConverter(dbRefResolver, mongoMappingContext);
        //去掉_class字段
        mappingConverter.setTypeMapper(new DefaultMongoTypeMapper(null));
        return new MongoTemplate(mongoDatabaseFactory,mappingConverter);
    }
}

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationListener;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.data.mongodb.core.convert.DefaultMongoTypeMapper;
import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
import org.springframework.data.mongodb.core.convert.MongoConverter;

/**
 * 作用： 去除Mongo中的_class
 */
@Configuration
public class ApplicationReadyListener implements ApplicationListener<ContextRefreshedEvent> {

    @Autowired
    MongoTemplate mongoTemplate;

    @Override
    public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
        MongoConverter converter = mongoTemplate.getConverter();
        if (converter.getTypeMapper().isTypeKey("_class")) {
            ((MappingMongoConverter) converter).setTypeMapper(new DefaultMongoTypeMapper(null));
        }
    }
}