SpringMvc 源码分析 (异常处理流程) (十三)

文章目录

0.前记

根据之前的文章​​DispatcherServlet.doDisptcher()​​​方法中的方法​​ha.handle​​​返回​​ModelAndView​​​处理的方法​​processDispatchResult​​

private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
      @Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv,
      @Nullable Exception exception) throws Exception {

    boolean errorView = false;

    if (exception != null) {
      if (exception instanceof ModelAndViewDefiningException) {
        logger.debug("ModelAndViewDefiningException encountered", exception);
        mv = ((ModelAndViewDefiningException) exception).getModelAndView();
      }
      else {
        Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
        mv = processHandlerException(request, response, handler, exception);
        errorView = (mv != null);
      }
    }

1.processHandlerException方法

这个方法就是如果出现异常的话, 异常解析器进行处理异常。

1. 先判断是否是​​@ExceptionHandler​​​注解下的方法, 如果是的话另外处理​​AbstractHandlerMethodExceptionResolver.doResolveException()​​​ ->​​ExceptionHandlerExceptionResolver.doResolveHandlerMethodException()​​
2. 判断是否是​​@ResponseStatus​​​注解下的方法​​RespinseStatusExceptionResolver.doResolveException​​
3. ​​DefaultHandlerExceptionResolver.doResolveException()​​

这里的​​HandlerExceptionResolver​​主要有3个实现类

1.1​​@ExceptionHandler​​注解下的异常

​​AbstractHandlerMethodExceptionResolver.doResolveException()​​

1.2​​@ResponseStatus​​注解下的方法

protected ModelAndView resolveResponseStatus(ResponseStatus responseStatus, HttpServletRequest request,
      HttpServletResponse response, @Nullable Object handler, Exception ex) throws Exception {

    int statusCode = responseStatus.code().value();
    String reason = responseStatus.reason();
    return applyStatusAndReason(statusCode, reason, response);
  }

1. 获取到装填码
2. 获取到出错理由
3. 然后渲染异常的页面
4. 返回空的ModelAndView

1.3​​DefaultHandlerExceptionResolver​​解析方法

这里比如​​handleMissingServletRequestParameter​​​ 这个 ​​return​​

会跳转页面 + 返回空的ModelAndView