解决js处理Long类型丢失精度的问题

一、前端解决

在发起ajax请求后，因为后台返回的是Json的字符串，在axios内部会自动调用 JSON.parse()方法把json字符串转为js数据，就会出现进度损失。如果不进行转换，依然当做字符串来使用，就不会有问题了。

1.1 解决方案

重写axios对响应的处理回调函数

1.2 前提条件

请求的返回数据为Long类型的数据

二、后端解决

2.1 Jackson

Spring MVC中默认是使用了Jackson的。通过重写转换器解决。

注意添加两个注解。

package com.leyou.order.config;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
import com.leyou.order.interceptor.LoginInterceptor;
import com.leyou.order.properties.JwtProperties;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.StringHttpMessageConverter;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

import java.math.BigInteger;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;

/**
 * @author: 98050
 * @create: 2018-10-27
 **/
@Configuration
@EnableWebMvc
public class MvcConfig implements WebMvcConfigurer {


    @Override
    public void configureMessageConverters(List> converters) {

        MappingJackson2HttpMessageConverter jackson2HttpMessageConverter =
                new MappingJackson2HttpMessageConverter();

        ObjectMapper objectMapper = new ObjectMapper();
        SimpleModule simpleModule = new SimpleModule();
        simpleModule.addSerializer(BigInteger.class, ToStringSerializer.instance);
        simpleModule.addSerializer(Long.class, ToStringSerializer.instance);
        simpleModule.addSerializer(Long.TYPE, ToStringSerializer.instance);
        objectMapper.registerModule(simpleModule);
        jackson2HttpMessageConverter.setObjectMapper(objectMapper);
        converters.add(jackson2HttpMessageConverter);
        converters.add(new StringHttpMessageConverter(Charset.forName("UTF-8")));
    }

}

2.2 Fastjson

在Spring Boot中将Jackson替换为fastjson一般会有两种方式：

第一种：

@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {

    @Bean
    public HttpMessageConverters fastJsonHttpMessageConverter() {
        return new HttpMessageConverters(new FastJsonHttpMessageConverter());
    }
}

第二种：

@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {

    @Override
    public void configureMessageConverters(List> converters) {
        FastJsonHttpMessageConverter fastConverter = 
        new FastJsonHttpMessageConverter();

        FastJsonConfig fastJsonConfig = new FastJsonConfig();
        fastJsonConfig.setSerializerFeatures(SerializerFeature.PrettyFormat);
        fastConverter.setFastJsonConfig(fastJsonConfig);
        converters.add(fastConverter);
    }
}

替换成fastjson之后，对于精度丢失问题，解决方法如下：

@EnableWebMvc
@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {

    @Override
    public void configureMessageConverters(List> converters) {
        FastJsonHttpMessageConverter fastConverter = 
        new FastJsonHttpMessageConverter();

        FastJsonConfig fastJsonConfig = new FastJsonConfig();
        SerializeConfig serializeConfig = SerializeConfig.globalInstance;
        serializeConfig.put(BigInteger.class, ToStringSerializer.instance);
        serializeConfig.put(Long.class, ToStringSerializer.instance);
        serializeConfig.put(Long.TYPE, ToStringSerializer.instance);
        fastJsonConfig.setSerializeConfig(serializeConfig);
        fastConverter.setFastJsonConfig(fastJsonConfig);
        converters.add(fastConverter);
    }
}