记录mongoTemplate插入时，不保存.class列

直接添加mongo的配置类即可。

@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));
        }
    }
}