SpringMvc 源码分析 (异常处理流程) (十三)

• • • 0.前记
    • 1.processHandlerException方法
    • • 1.1`@ExceptionHandler`注解下的异常
      • 1.2`@ResponseStatus`注解下的方法
      • 1.3`DefaultHandlerExceptionResolver`解析方法

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);
			}
		}

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

AbstractHandlerMethodExceptionResolver.doResolveException()

	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

这里比如handleMissingServletRequestParameter 这个 return

会跳转页面 + 返回空的ModelAndView