# bugDiary

**Repository Path**: studygo/bug-diary

## Basic Information

- **Project Name**: bugDiary
- **Description**: 日常开发常见/重难点bug记录
- **Primary Language**: Java
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2021-10-16
- **Last Updated**: 2022-01-04

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# bugDiary

### 介绍
**日常开发常见/重难点bug记录**

---

##### 1.接口返回Long类型,前端js的Number类型容量不够,导致精度丢失 (@JsonSerialize(using = ToStringSerializer.class))
- 案例: 订单列表查询接口,订单在库中bigint类型长度19位,响应给前端时,前端显示的都是同样的id号.
- 造成原因: java中long数据能表示的范围比js中number大,在跟前端交互时,可能造成long类型数据响应到前端js中的number类型变量存储不下
- 处理方式: 在映射的实体类Long类型字段上都加上@JsonSerialize(using = ToStringSerializer.class) 注解; 使用fastjson的ToStringSerializer注解，让系统序列化时，保留相关精度
    
    ```
        package com.fasterxml.jackson.databind.annotation;
        /**
          * 主键ID
         */
        @JsonSerialize(using = ToStringSerializer.class)
        private Long orderId;
   
    ```
    
- 补充说明: 关于这个注解的方法，可以自己定义class, 作为using的值来使用. 还可以 using = DateToLongSerializer.class,当转成json时,将Date类型转换为秒Long
    ```
        /** 订单创建时间 */
        @JsonSerialize(using = DateToLongSerializer.class)
        private Date createTime;     
    ``` 
   
##### 2.数据表映射的实体pojo类中,Date类型字段,没有限定时区,查询时反序列化映射的错误的时间.需要在该字段上加注解
@JsonFormat(pattern = "yyyy-MM-dd", timezone = "GMT+8")     
   - 说明: timezone = "GMT+8"是指定东八区北京时间
    ```
        @JsonFormat(pattern = "yyyy-MM-dd", timezone = "GMT+8")
        private Date createTime;
    ```
   
#### 3.过滤器解决跨域问题
- 原doFilter方法:
```
@Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        // 解决跨域
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        response.setHeader("Access-Control-Allow-Origin", "*");
        response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");
        response.setHeader("Access-Control-Max-Age", "0");
        response.setHeader("Access-Control-Allow-Headers", "Origin, No-Cache, X-Requested-With, If-Modified-Since, Pragma, Last-Modified, Cache-Control, Expires, Content-Type, X-E4M-With, Authorization,DeviceCode");
        response.setHeader("Access-Control-Allow-Credentials", "true");
        if(request.getMethod().equals("OPTIONS")){
            return;
        }
        servletResponse.setCharacterEncoding("UTF-8");
        Subject subject = parseLoginToken(request,response);
        String requestsUri = request.getRequestURI();
        String ctxPath = request.getContextPath();
        String url = requestsUri.substring(ctxPath.length());
        if ( notLoginUrls.contains(url) && Objects.isNull(subject) ) {
            filterChain.doFilter(servletRequest, servletResponse);
        } else {
            response.addHeader("Content-Type", "application/json; charset=utf-8");
            response.setHeader("Access-Control-Expose-Headers", HERDER_AUTHORIZATION);
            if (Objects.nonNull(subject)) {
                servletRequest.setAttribute("username", subject.getUsername());
                servletRequest.setAttribute("unionId", subject.getUnionId());
                servletRequest.setAttribute("role", subject.getRole());
                filterChain.doFilter(servletRequest, servletResponse);
                return;
            }
            try (PrintWriter writer = servletResponse.getWriter()){
                RestFullResponse<Object> baseResponse = RestFullResponse.fail(RestFullCode.NOT_LOGIN);
                char[] chars = JSONObject.toJSONString(baseResponse).toCharArray();
                writer.write(chars);
                writer.flush();
            }
        }
    }
```
- 修正跨域后的doFilter方法
```
@Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        // 解决跨域
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        response.setHeader("Access-control-Allow-Origin", "*");
        response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");
        response.setHeader("Access-Control-Max-Age", "3600");
        response.setHeader("Access-Control-Allow-Headers", "Origin, No-Cache, X-Requested-With, If-Modified-Since, Pragma, Last-Modified, Cache-Control, Expires, Content-Type, X-E4M-With, Authorization,DeviceCode");
        response.setHeader("Access-Control-Allow-Credentials", "true");
        if(request.getMethod().equals("OPTIONS")){
            response.setStatus(HttpServletResponse.SC_OK);
            return;
        }
        servletResponse.setCharacterEncoding("UTF-8");
        Subject subject = parseLoginToken(request,response);
        String requestsUri = request.getRequestURI();
        String ctxPath = request.getContextPath();
        String url = requestsUri.substring(ctxPath.length());
        if ( notLoginUrls.contains(url) && Objects.isNull(subject) ) {
            filterChain.doFilter(servletRequest, servletResponse);
        } else {
            response.addHeader("Content-Type", "application/json; charset=utf-8");
            response.setHeader("Access-Control-Expose-Headers", HERDER_AUTHORIZATION);
            if (Objects.nonNull(subject)) {
                servletRequest.setAttribute("username", subject.getUsername());
                servletRequest.setAttribute("unionId", subject.getUnionId());
                servletRequest.setAttribute("role", subject.getRole());
                filterChain.doFilter(servletRequest, servletResponse);
                return;
            }
            try (PrintWriter writer = servletResponse.getWriter()){
                RestFullResponse<Object> baseResponse = RestFullResponse.fail(RestFullCode.NOT_LOGIN);
                char[] chars = JSONObject.toJSONString(baseResponse).toCharArray();
                writer.write(chars);
                writer.flush();
            }
        }
    }
```