使用SpringBoot的版本是 1.5.12.RELEASE

添加一个配置文件就可以了

import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.mongodb.MongoDbFactory;
import org.springframework.data.mongodb.core.convert.*;
import org.springframework.data.mongodb.core.mapping.MongoMappingContext;

@Configuration
public class MongoConfig {

    @Bean
    public MappingMongoConverter mappingMongoConverter(MongoDbFactory factory, MongoMappingContext context, BeanFactory beanFactory) {
        DbRefResolver dbRefResolver = new DefaultDbRefResolver(factory);
        MappingMongoConverter mappingConverter = new MappingMongoConverter(dbRefResolver, context);
        try {
            mappingConverter.setCustomConversions(beanFactory.getBean(CustomConversions.class));
        } catch (NoSuchBeanDefinitionException ignore) {
        }

        // Don't save _class to mongo
        mappingConverter.setTypeMapper(new DefaultMongoTypeMapper(null));

        return mappingConverter;
    }
}