一次请求在SpringMVC核心执行流程

 

org.springframework.web.servlet.DispatcherServlet#doDispatch

1.1 获取执行调用链HandlerExecutionChain
1.2 获取处理器适配器HandlerAdapter
1.3 调用拦截器preHandle
1.4 调用适配器的handle方法
1.5 处理视图名
1.6 调用postHandle方法
1.7 视图渲染

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 {

 // 检查是否多模块请求
 processedRequest = checkMultipart(request);
 multipartRequestParsed = (processedRequest != request);

 // Determine handler for the current request.

 // 通过HandlerMapping根据url获取HandlerMethod, 再获取拦截器, 组合起来创建出调用执行链HandlerExecutionChain对象(HandlerMethod + 拦截器)
 mappedHandler = getHandler(processedRequest);
 if (mappedHandler == null) {
 noHandlerFound(processedRequest, response);
 return;
 }

 // Determine handler adapter for the current request.

 // 获取处理器适配器, 根据不同种类的适配器支持程度supports方法, 获取到合适的适配器, 处理的核心方法为handle方法
 // mappedHandler.getHandler()获取的是HandlerMethod对象
 HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

 // Process last-modified header, if supported by the handler.
 String method = request.getMethod();
 boolean isGet = "GET".equals(method);
 if (isGet || "HEAD".equals(method)) {
 long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
 if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
 return;
 }
 }

 // 处理拦截器preHandle方法
 if (!mappedHandler.applyPreHandle(processedRequest, response)) {
 return;
 }

 // Actually invoke the handler.

 // 调用HandlerAdapter的handle方法
 mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

 if (asyncManager.isConcurrentHandlingStarted()) {
 return;
 }

 // 处理视图名字
 applyDefaultViewName(processedRequest, mv);

 // 处理拦截器postHandle方法
 mappedHandler.applyPostHandle(processedRequest, response, mv);
 }
 catch (Exception ex) {
 dispatchException = ex;
 }
 catch (Throwable err) {
 // As of 4.3, we're processing Errors thrown from handler methods as well,
 // making them available for @ExceptionHandler methods and other scenarios.
 dispatchException = new NestedServletException("Handler dispatch failed", err);
 }

 // 处理视图渲染
 processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
 }
 catch (Exception ex) {
 triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
 }
 catch (Throwable err) {
 triggerAfterCompletion(processedRequest, response, mappedHandler,
 new NestedServletException("Handler processing failed", err));
 }
 finally {
 if (asyncManager.isConcurrentHandlingStarted()) {
 // Instead of postHandle and afterCompletion
 if (mappedHandler != null) {
 mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
 }
 }
 else {
 // Clean up any resources used by a multipart request.
 if (multipartRequestParsed) {
 cleanupMultipart(processedRequest);
 }
 }
 }
}