【推薦】SpringMVC原始碼總結（一）HandlerMapping和HandlerAdapter入門
阿新 • • 發佈：2019-01-23
- 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 {
- processedRequest = checkMultipart(request);
- multipartRequestParsed = (processedRequest != request);
- //這個是重點，第一步由HandlerMapping找到對應的handler
- // Determine handler for the current request.
- mappedHandler = getHandler(processedRequest);
- if (mappedHandler == null || mappedHandler.getHandler() == null) {
- noHandlerFound(processedRequest, response);
- return;
- }
- // Determine handler adapter for the current request.
- //這是第二步，找到合適的HandlerAdapter，然後由它來排程執行handler的方法
- 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 (logger.isDebugEnabled()) {
- logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);
- }
- if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
- return;
- }
- }
- if (!mappedHandler.applyPreHandle(processedRequest, response)) {
- return;
- }
- try {
- // Actually invoke the handler.
- mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
- }
- finally {
- if (asyncManager.isConcurrentHandlingStarted()) {
- return;
- }
- }
- applyDefaultViewName(request, mv);
- mappedHandler.applyPostHandle(processedRequest, response, mv);
- }
- catch (Exception ex) {
- dispatchException = ex;
- }
- processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
- }
- catch (Exception ex) {
- triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
- }
- catch (Error err) {
- triggerAfterCompletionWithError(processedRequest, response, mappedHandler, err);
- }
- finally {
- if (asyncManager.isConcurrentHandlingStarted()) {
- // Instead of postHandle and afterCompletion
- mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
- return;
- }
- // Clean up any resources used by a multipart request.
- if (multipartRequestParsed) {
- cleanupMultipart(processedRequest);
- }
- }
- }