c2c网站有哪几个/网络营销师怎么考

子容器创建完成后，当有请求到来时，DispatcherServlet就可以进行分发处理了。我们首先根据Servlet规范查找doService()方法，这个方法在DispatcherServlet本身就有实现：

@Override protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {// ... ... try { doDispatch(request, response); } finally { // ... ... }

我们省去了无关代码，于是可以明显看出doDispatch()才是分发请求的主要实现方法：

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception { HttpServletRequest processedRequest = request; HandlerExecutionChain mappedHandler = null; boolean multipartRequestParsed = false; WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request); try { ModelAndView mv = null; Exception dispatchException = null; try { // 查检是否是文件上传请求 processedRequest = checkMultipart(request); multipartRequestParsed = (processedRequest != request); // 查找能够处理当前请求的Handler mappedHandler = getHandler(processedRequest); if (mappedHandler == null || mappedHandler.getHandler() == null) { noHandlerFound(processedRequest, response); return; } // 查找能够处理当前请求的Handler Adapter HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler()); // ... ... // 拦截器的preHandle()方法就是在这里被调用的 // 可见，如果preHandle()方法返回false,则终止分发流程，直接返回 if (!mappedHandler.applyPreHandle(processedRequest, response)) { return; } try { // 这一行是对我们写的Controller方法的真正调用 mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); } finally { if (asyncManager.isConcurrentHandlingStarted()) { return; } } applyDefaultViewName(request, mv); // 拦截器的postHandle()方法就是在这里被调用的，即在Controller调用完成之后 mappedHandler.applyPostHandle(processedRequest, response, mv); } catch (Exception ex) { dispatchException = ex; } processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException); } catch (Exception ex) { // ... ... } finally { // ... ... } }

分析到这里，DispatcherServlet的分发请求处理流程就一目了然了。

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