精尽Spring MVC源码分析 - HandlerExceptionResolver 组件 (3)

prepareResponse(Exception ex, HttpServletResponse response) 方法，阻止响应缓存，方法如下：

protected void prepareResponse(Exception ex, HttpServletResponse response) { if (this.preventResponseCaching) { preventCaching(response); } } /** * Prevents the response from being cached, through setting corresponding * HTTP {@code Cache-Control: no-store} header. * @param response current HTTP response */ protected void preventCaching(HttpServletResponse response) { response.addHeader(HEADER_CACHE_CONTROL, "no-store"); }

如果想要阻止响应缓存，需要设置 preventResponseCaching 为 true

resolveException

实现 resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) 方法，代码如下：

@Override @Nullable public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, @Nullable Object handler, Exception ex) { // <1> 判断是否可以应用 if (shouldApplyTo(request, handler)) { // <1.1> 阻止缓存 prepareResponse(ex, response); // <1.2> 执行解析异常，返回 ModelAndView 对象 ModelAndView result = doResolveException(request, response, handler, ex); // <1.3> 如果 ModelAndView 对象非空，则打印日志 if (result != null) { // Print debug message when warn logger is not enabled. if (logger.isDebugEnabled() && (this.warnLogger == null || !this.warnLogger.isWarnEnabled())) { logger.debug("Resolved [" + ex + "]" + (result.isEmpty() ? "" : " to " + result)); } // Explicitly configured warn logger in logException method. logException(ex, request); } // <1.4> 返回执行结果 return result; } // <2> 不可应用，直接返回 null else { return null; } } @Nullable protected abstract ModelAndView doResolveException( HttpServletRequest request, HttpServletResponse response, @Nullable Object handler, Exception ex);

调用 shouldApplyTo(HttpServletRequest request, Object handler) 方法，判断是否可以应用，如果可以应用

调用 prepareResponse(Exception ex, HttpServletResponse response) 方法，阻止缓存

调用 doResolveException(HttpServletRequest request, HttpServletResponse response, @Nullable Object handler, Exception ex) 抽象方法，执行解析异常，返回 ModelAndView 对象

如果 ModelAndView 对象非空，则打印日志

返回执行结果

不可应用，直接返回 null

AbstractHandlerMethodExceptionResolver

org.springframework.web.servlet.handler.AbstractHandlerMethodExceptionResolver，继承 AbstractHandlerExceptionResolver 抽象类，基于 handler 类型为 HandlerMethod 的 HandlerExceptionResolver 抽象类。

可能你会有疑惑，为什么 AbstractHandlerMethodExceptionResolver 只有一个 ExceptionHandlerExceptionResolver 子类，为什么还要做抽象呢？因为 ExceptionHandlerExceptionResolver 是基于 @ExceptionHandler 注解来配置对应的异常处理器，而如果未来我们想自定义其它的方式来配置对应的异常处理器，就可以来继承 AbstractHandlerMethodExceptionResolver 这个抽象类。