雪花ID算法 - Long 类型 id 返回前端精度丢失 （通过序列化解决）

原因：

js 的 number 类型支持的最大值是9007199254740992 （2 的 53次方 -1），溢出之后的精度会丢失，导致前后端的值不一致。
java 的 long 类型最大值为 9223372036854775807，远高于 js number类型的最大值，所以这个坑就出现了。

解决方案：

方案一

1. id-type: ID_WORKER_STR
   简单来说就是 id 转 为string类型，db和生成的id数据类型都改为 string 类型
   缺点：牺牲了 long 类型的性能优势

方案二

可以在每个实体类的id字段上加注解

	@JsonFormat(shape = JsonFormat.Shape.STRING)
	private Long id;

方案三

1. 通过 json 序列化做全局处理，传给前端的是字符串，到后台依然是 long 类型

   
   import com.alibaba.fastjson.serializer.SerializerFeature;
   import com.alibaba.fastjson.serializer.ValueFilter;
   import com.alibaba.fastjson.support.config.FastJsonConfig;
   import com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter;
   import org.apache.commons.lang3.StringUtils;
   import org.springframework.boot.autoconfigure.http.HttpMessageConverters;
   import org.springframework.context.annotation.Bean;
   import org.springframework.context.annotation.Configuration;
   import org.springframework.http.converter.HttpMessageConverter;
   
   import java.util.ArrayList;
   import java.util.List;
   
   /**
    * @author ：XiaoHui Yang
    * @version : 1.0.0
    * @description: 自定义JsonHttpMessageConverter解决long类型id丢精度问题
    * @date ：Created in 2020/6/28 14:41
    * @modified By：
    */
   @Configuration
   public class CustomFastJsonHttpMessageConverter {
   
       @Bean
       public HttpMessageConverters fastJsonHttpMessageConverters() {
           FastJsonHttpMessageConverter fastConverter = new FastJsonHttpMessageConverter();
           FastJsonConfig fastJsonConfig = new FastJsonConfig();
   
           List<SerializerFeature> list = new ArrayList<>();
           list.add(SerializerFeature.PrettyFormat);
           list.add(SerializerFeature.WriteMapNullValue);
           list.add(SerializerFeature.WriteNullStringAsEmpty);
           list.add(SerializerFeature.WriteNullListAsEmpty);
           list.add(SerializerFeature.QuoteFieldNames);
           list.add(SerializerFeature.WriteDateUseDateFormat);
           list.add(SerializerFeature.DisableCircularReferenceDetect);
           list.add(SerializerFeature.WriteBigDecimalAsPlain);
   
           fastJsonConfig.setSerializerFeatures(list.toArray(new SerializerFeature[list.size()]));
   
           fastConverter.setFastJsonConfig(fastJsonConfig);
           HttpMessageConverter<?> converter = fastConverter;
           fastJsonConfig.setSerializeFilters(new ValueFilter() {
               @Override
               public Object process(Object object, String name, Object value) {
                   if ((StringUtils.endsWith(name, "Id") || StringUtils.equals(name,"id")) && value != null
                           && value.getClass() == Long.class) {
                       return String.valueOf(value);
                   }
                   return value;
               }
           });
           return new HttpMessageConverters(converter);
       }
   }
   
   

   @Configuration
   public class WebConfig extends WebMvcConfigurationSupport {
       /*处理返回的long类型前端无法显示问题*/
       @Override
       public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
           MappingJackson2HttpMessageConverter jackson2HttpMessageConverter = new MappingJackson2HttpMessageConverter();
           ObjectMapper objectMapper = new ObjectMapper();
           /**
            * 日期全局格式化
            * */
           objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
           objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
           objectMapper.setTimeZone(TimeZone.getTimeZone("GMT+8"));//GMT+8
           /**
            * 序列换成json时,将所有的long变成string
            * 因为js中得数字类型不能包含所有的java long值
            */
           SimpleModule simpleModule = new SimpleModule();
           simpleModule.addSerializer(Long.class, ToStringSerializer.instance);
           simpleModule.addSerializer(Long.TYPE, ToStringSerializer.instance);
           objectMapper.registerModule(simpleModule);
           jackson2HttpMessageConverter.setObjectMapper(objectMapper);
           converters.add(jackson2HttpMessageConverter);
   
       }
   
       /*处理swagger doc.html无法显示问题*/
       @Override
       protected void addResourceHandlers(ResourceHandlerRegistry registry) {
           registry.addResourceHandler("doc.html").addResourceLocations("classpath:/META-INF/resources/");
           registry.addResourceHandler("/webjars/**").addResourceLocations("classpath:/META-INF/resources/webjars/");
       }
   }