使用@ControllerAdvice + @ExceptionHandler建立全局異常攔截

1. @ControllerAdvice 註解定義全局異常處理類

   @ControllerAdvice
   public class GlobalExceptionHandler {
   }
   

2. @ExceptionHandler 註解聲明異常處理方法

   @ControllerAdvice
   public class GlobalExceptionHandler{
       @ExceptionHandler(Exception.class)
       @ResponseBody
       public String handleException() {
           ex.printStackTrace(); 
           return "fail";
       }
   }
   

   方法handleException()會處理所有Controller層拋出的Exception及其子類的異常，Controller層就不需要單獨處理異常了。
   但如上代碼只能處理 Controller 層的異常，對於未進入Controller的異常，如Interceptor（攔截器）層的異常，Spring 框架層的異常無效，還是會將錯誤直接返回給用戶。對此，只需要在配置文件中添加：

   spring.mvc.throw-exception-if-no-handler-found=true
   spring.resources.add-mappings=false
   

3. 被 @ExceptionHandler 註解的方法還可以聲明很多種參數類型，具體可以參考文檔：https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/bind/annotation/ExceptionHandler.html
   這裏我選擇了httpServletRequest, HttpServletResponse httpServletResponse, Exception ex三個參數，應用如下：

   @ControllerAdvice
   public class GlobalExceptionHandler{
       @ExceptionHandler(Exception.class)
       @ResponseBody
       public CommonReturnType handleException(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Exception ex) {
           ex.printStackTrace(); // 線上環境替換爲對應的log
           Map<String,Object> responseData = new HashMap<>();
           if( ex instanceof BusinessException){
               BusinessException businessException = (BusinessException)ex;
               responseData.put("errCode",businessException.getErrCode());
               responseData.put("errMsg",businessException.getErrMsg());
           }else if(ex instanceof ServletRequestBindingException){
               responseData.put("errCode",BusinessError.UNKNOWN_ERROR.getErrCode());
               responseData.put("errMsg","url綁定路由問題");
           }else if(ex instanceof NoHandlerFoundException){
               responseData.put("errCode",BusinessError.UNKNOWN_ERROR.getErrCode());
               responseData.put("errMsg","沒有找到對應的訪問路徑");
           }else{
               responseData.put("errCode", BusinessError.UNKNOWN_ERROR.getErrCode());
               responseData.put("errMsg", BusinessError.UNKNOWN_ERROR.getErrMsg());
           }
           return CommonReturnType.create(responseData,"fail");
       }
   }
   

如此，所有的 Controller 層的異常日誌都可以通過GlobalExceptionHandler 記錄。Controller 層也不需要在手動記錄異常日誌了。