Spring请求过程

港控/mmm° 2022-05-17 13:04 148阅读 0赞

/** * Process the actual dispatching to the handler. * <p>The handler will be obtained by applying the servlet's HandlerMappings in order. * The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters * to find the first that supports the handler class. * <p>All HTTP methods are handled by this method. It's up to HandlerAdapters or handlers * themselves to decide which methods are acceptable. * @param request current HTTP request * @param response current HTTP response * @throws Exception in case of any kind of processing failure */
        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);
    
                    // 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.
                    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);
                }
            }
        }