From d57863e0d5252a78e5eae81157be161bc0765472 Mon Sep 17 00:00:00 2001
From: LGH <1242479791@qq.com>
Date: Sun, 26 Apr 2020 08:19:00 +0800
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+## 后台异常处理
+
+在开发过程中，不可避免的是需要处理各种异常，异常处理方法随处可见，所以代码中就会出现大量的`try {...} catch {...} finally {...}` 代码块，不仅会造成大量的冗余代码，而且还影响代码的可读性，所以对异常统一处理非常有必要。为此，我们定义了一个统一的异常类`YamiShopBindException` 与异常管理类 `DefaultExceptionHandlerConfig`。
+
+我们先来看下 `YamiShopBindException`的代码
+
+```java
+public class YamiShopBindException extends RuntimeException {
+
+    private static final long serialVersionUID = -4137688758944857209L;
+
+    /**
+     * http状态码
+     */
+    private Integer httpStatusCode;
+
+    /**
+     * @param httpStatus http状态码
+     */
+    public YamiShopBindException(YamiHttpStatus httpStatus) {
+        super(httpStatus.getMsg());
+        this.httpStatusCode = httpStatus.value();
+    }
+
+    /**
+     * @param httpStatus http状态码
+     */
+    public YamiShopBindException(YamiHttpStatus httpStatus, String msg) {
+        super(msg);
+        this.httpStatusCode = httpStatus.value();
+    }
+
+    public YamiShopBindException(String msg) {
+        super(msg);
+        this.httpStatusCode = HttpStatus.BAD_REQUEST.value();
+    }
+
+    public Integer getHttpStatusCode() {
+        return httpStatusCode;
+    }
+
+}
+```
+
+`YamiHttpStatus`为我们自定义的返回状态码的枚举类，定义为一个枚举类，更直观处理异常返回的状态码及异常内容，以后每增加一种异常情况，只需增加一个枚举实例即可，不用每一种异常都定义一个异常类。
+
+```java
+public enum YamiHttpStatus {
+    /**
+     * 客户端看到401状态码时，应该重新登陆
+     */
+    UNAUTHORIZED(401, "未授权"),
+
+    COUPONCANNOTUSETOGETHER(601, "优惠券不能共用"),
+    ;
+
+    private final int value;
+
+    private final String msg;
+
+    YamiHttpStatus(int value, String msg) {
+        this.value = value;
+        this.msg = msg; 
+    }
+
+    public int value() {
+        return this.value;
+    }
+
+    public String getMsg() {
+        return msg;
+    }
+    
+    public static YamiHttpStatus resolve(int statusCode) {
+        for (YamiHttpStatus status : values()) {
+            if (status.value == statusCode) {
+                return status;
+            }
+        }
+        return null;
+    }
+}
+```
+
+再来看看 `DefaultExceptionHandlerConfig`类
+
+```java
+@Controller
+@RestControllerAdvice
+public class DefaultExceptionHandlerConfig {
+    
+
+    @ExceptionHandler(YamiShopBindException.class)
+    public ResponseEntity<String> unauthorizedExceptionHandler(YamiShopBindException e){
+        e.printStackTrace();
+        return ResponseEntity.status(e.getHttpStatusCode()).body(e.getMessage());
+    }
+}
+```
+
+
+
+## 前台异常处理
+
+
+
+前端请求与相应做了封装，请求响应的内容会被拦截器所拦截，当后台返回给前台特定的状态码，前台将显示不同报错信息。请求响应非常常见，我们查看在`src\utils\httpRequest.js`里面的其中一段代码
+
+
+
+```javascript
+http.interceptors.response.use(response => {
+  return response
+}, error => {
+  switch (error.response.status) {
+    case 400:
+      Message.error(error.response.data)
+      break
+    case 401:
+      clearLoginInfo()
+      router.push({ name: 'login' })
+      break
+    case 405:
+      Message.error('http请求方式有误')
+      break
+    case 500:
+      Message.error('服务器出了点小差，请稍后再试')
+      break
+    case 501:
+      Message.error('服务器不支持当前请求所需要的某个功能')
+      break
+  }
+  return Promise.reject(error)
+})
+```
+
+这里将会统一拦截返回的状态码如`400`，进行错误提示。
+
+
+
+##  RESTful 风格
+
+我们的上述代码使用http状态码对请求进行统一响应，其中最大的 
+
+RESTful架构，就是目前最流行的一种互联网软件架构。它结构清晰、符合标准、易于理解、扩展方便，所以正得到越来越多网站的采用。
+
+ 
+
+[RESTful概述](https://blog.igevin.info/posts/restful-architecture-in-general/)