long类型精度丢失问题的三种解决方案 (在Long长度大于17位时会出现精度丢失的问题)

1. 简介

​ 对于Long类型的数据，如果我们在Controller层将结果序列化为json，直接传给前端的话，在Long长度大于17位时会出现精度丢失的问题

2. 解决方案

2.1 注解

2.1.1 @JsonFormat

 @JsonFormat(shape =JsonFormat.Shape.STRING)

2.1.2 @JsonSerialize

@JsonSerialize(using = ToStringSerializer.class)

2.1.3 详情

package com.king.entity;

import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
import lombok.Data;
import lombok.EqualsAndHashCode;

import java.io.Serializable;

/**
 * @author King
 * @version 1.0
 * @description TODO
 * @date 2023/9/5 10:19
 */
@Data
@EqualsAndHashCode(callSuper = false)
public class user implements Serializable {
    //方式一
    @JsonFormat(shape = JsonFormat.Shape.STRING)
    private Long id;
    private String username;
    private String password;
    //方式二
    @JsonSerialize(using = ToStringSerializer.class)
    private String userId;
}

2.2 ObjectMapper

在spring boot的启动类或者spring的配置类里面添加bean

/**
    * @description Long类型精度类型丢失
    * @param mapperBuilder 
    * @return com.fasterxml.jackson.databind.ObjectMapper
    * @author King
    * @date 2023/9/5 10:33
    */
    @Bean
    public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder mapperBuilder) {
        ObjectMapper build = mapperBuilder.createXmlMapper(false).build();
        build.setSerializationInclusion(JsonInclude.Include.NON_NULL);
        SimpleModule module = new SimpleModule();    
        module.addSerializer(Long.class, ToStringSerializer.instance);
        module.addSerializer(Long.TYPE, ToStringSerializer.instance);
        build.registerModule(module);
        return build;

    }