The execution process of springmvc: A request executes the DispatcherServlet's doService method: protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception { if (logger.isDebugEnabled()) { String resumed = WebAsyncUtils.getAsyncManager(request).hasConcurrentResult() ? " resumed" : ""; logger.debug("DispatcherServlet with name '" + getServletName() + "'" + resumed + " processing " + request.getMethod() + " request for [" + getRequestUri(request) + "]"); } // Keep a snapshot of the request attributes in case of an include, // to be able to restore the original attributes after the include. Map<String, Object> attributesSnapshot = null; if (WebUtils.isIncludeRequest(request)) { attributesSnapshot = new HashMap<String, Object>(); Enumeration<?> attrNames = request.getAttributeNames(); while (attrNames.hasMoreElements()) { String attrName = (String) attrNames.nextElement(); if (this.cleanupAfterInclude || attrName.startsWith("org.springframework.web.servlet")) { attributesSnapshot.put(attrName, request.getAttribute(attrName)); } } } // Make framework objects available to handlers and view objects. request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext()); request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver); request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver); request.setAttribute(THEME_SOURCE_ATTRIBUTE, getThemeSource()); FlashMap inputFlashMap = this.flashMapManager.retrieveAndUpdate(request, response); if (inputFlashMap != null) { request.setAttribute(INPUT_FLASH_MAP_ATTRIBUTE, Collections.unmodifiableMap(inputFlashMap)); } request.setAttribute(OUTPUT_FLASH_MAP_ATTRIBUTE, new FlashMap()); request.setAttribute(FLASH_MAP_MANAGER_ATTRIBUTE, this.flashMapManager); try { // schedule here doDispatch(request, response); } finally { if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) { // Restore the original attribute snapshot, in case of an include. if (attributesSnapshot != null) { restoreAttributesAfterInclude(request, attributesSnapshot); } } } } 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 { // Whether to convert to upload request processedRequest = checkMultipart(request); / / Determine whether it is an upload request multipartRequestParsed = (processedRequest != request); // Determine handler for the current request. //find Handler mappedHandler = getHandler(processedRequest, false); if (mappedHandler == null || mappedHandler.getHandler() == null) { noHandlerFound(processedRequest, response); return; } // Determine handler adapter for the current request. //Find HandlerAdapter through Handler 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; } // Actually invoke the handler. //execute handler mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); 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 if (mappedHandler != null) { mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response); } } else { // Clean up any resources used by a multipart request. if (multipartRequestParsed) { cleanupMultipart(processedRequest); } } } } protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception { //handlerMappings configured mapping handler for (HandlerMapping hm : this.handlerMappings) { if (logger.isTraceEnabled()) { logger.trace( "Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'"); } HandlerExecutionChain handler = hm.getHandler(request); if (handler != null) { return handler; } } return null; } public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception { //Get HandlerMethod. Object handler = getHandlerInternal(request); if (handler == null) { handler = getDefaultHandler (); } if (handler == null) { return null; } // Bean name or resolved handler? if (handler instanceof String) { String handlerName = (String) handler; handler = getApplicationContext (). getBean (handlerName); } //Getting HandlerExecutionChain is equivalent to adding HandlerMethod with spring interceptor. return getHandlerExecutionChain(handler, request); } protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception { //get uri String lookupPath = getUrlPathHelper().getLookupPathForRequest(request); if (logger.isDebugEnabled()) { logger.debug("Looking up handler method for path " + lookupPath); } // Equivalent to finding the method in the controller HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request); if (logger.isDebugEnabled()) { if (handlerMethod != null) { logger.debug("Returning handler method [" + handlerMethod + "]"); } else { logger.debug("Did not find handler method for [" + lookupPath + "]"); } } //Get the bean by beanname, here is to get the controller and set it to the handlerMethod return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null); } protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception { List<Match> matches = new ArrayList<Match>(); //urlMap encapsulates RequestMappingInfo with url as key List<T> directPathMatches = this.urlMap.get(lookupPath); if (directPathMatches != null) { //Add the matched ones to List<Match> addMatchingMappings(directPathMatches, matches, request); } if (matches.isEmpty()) { // No choice but to go through all mappings... addMatchingMappings(this.handlerMethods.keySet(), matches, request); } //find the most suitable match if (!matches.isEmpty()) { Comparator<Match> comparator = new MatchComparator(getMappingComparator(request)); Collections.sort(matches, comparator); if (logger.isTraceEnabled()) { logger.trace("Found " + matches.size() + " matching mapping(s) for [" + lookupPath + "] : " + matches); } Match bestMatch = matches.get(0); if (matches.size() > 1) { Match secondBestMatch = matches.get(1); if (comparator.compare(bestMatch, secondBestMatch) == 0) { Method m1 = bestMatch.handlerMethod.getMethod(); Method m2 = secondBestMatch.handlerMethod.getMethod(); throw new IllegalStateException( "Ambiguous handler methods mapped for HTTP path '" + request.getRequestURL() + "': {" + m1 + ", " + m2 + "}"); } } handleMatch(bestMatch.mapping, lookupPath, request); return bestMatch.handlerMethod; } else { return handleNoMatch(handlerMethods.keySet(), lookupPath, request); } } //Summary: springmvc first finds the corresponding Handler (equivalent to controller) according to our uri. In addition, the configured interceptor is encapsulated as a HandlerExecutionChain execution chain object. //Then find the appropriate HandlerAdapter adapter according to the handler. Finally, call the method of HandlerAdapter to return ModelAndView.
springmvc execution process
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