[技术笔记] 【杭州校区】SpringMVC源码剖析1——执行流程

SpringMVC源码剖析1——执行流程

00.SpringMVC执行流程
file:///C:/Users/WANGGA~1/AppData/Local/Temp/enhtmlclip/Image.png

01.拦截所有的请求,访问DispatcherServlet

02.DispatcherServlet原理是一个Servlet,只要是Servlet就走doService方法
下面是DispatcherServlet的doService方法

[Java] 纯文本查看 复制代码

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<>();
      Enumeration<?> attrNames = request.getAttributeNames();
      while (attrNames.hasMoreElements()) {
         String attrName = (String) attrNames.nextElement();
         if (this.cleanupAfterInclude || attrName.startsWith(DEFAULT_STRATEGIES_PREFIX)) {
            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());


   if (this.flashMapManager != null) {
      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 {
      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);
         }
      }
   }
}

前面都没啥用就是给request添加参数

03.doDispatch(request, response);方法

[Java] 纯文本查看 复制代码

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. 这段代码是用来确定调用方法的,是根据路径解析出来的
         mappedHandler = getHandler(processedRequest);
         if (mappedHandler == null) {
            noHandlerFound(processedRequest, response);
            return;
         }


         // Determine handler adapter for the current request. 
        //确定当前请求程序的适配器 [RequestMappingHandlerAdapter也是就@Controller 的适配器
         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.  通过反射调用相应执行的方法
         mv = ha.handle(processedRequest, response, mappedHandler.getHandler());


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


         applyDefaultViewName(processedRequest, mv);
         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);
      }
      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);
         }
      }
   }
}

04. mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
此方法主要是调用对应的适配器,然后再通过反射执行对应方法

本来应该调用RequestHandlerAdapter类中的方法,但是没有,根据继承的关系调用父类,抽象类AbstractHandlerMethodAdapter中的方法handle( )

[Java] 纯文本查看 复制代码

public final ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
      throws Exception {
   return handleInternal(request, response, (HandlerMethod) handler);
}

本类

[Java] 纯文本查看 复制代码

protected abstract ModelAndView handleInternal(HttpServletRequest request,HttpServletResponse response,
                                                                         HandlerMethod handlerMethod) throws Exception;

然后在RequestHandlerAdapter中调用 handleInternal( )方法

[Java] 纯文本查看 复制代码

protected ModelAndView handleInternal(HttpServletRequest request,
      HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {


   ModelAndView mav;
   checkRequest(request);


   // Execute invokeHandlerMethod in synchronized block if required.
   if (this.synchronizeOnSession) {
      HttpSession session = request.getSession(false);
      if (session != null) {
         Object mutex = WebUtils.getSessionMutex(session);
         synchronized (mutex) {
            mav = invokeHandlerMethod(request, response, handlerMethod);
         }
      }
      else {
         // No HttpSession available -> no mutex necessary
         mav = invokeHandlerMethod(request, response, handlerMethod);
      }
   }
   else {
      // No synchronization on session demanded at all...
      mav = invokeHandlerMethod(request, response, handlerMethod);
   }


   if (!response.containsHeader(HEADER_CACHE_CONTROL)) {
      if (getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) {
         applyCacheSeconds(response, this.cacheSecondsForSessionAttributeHandlers);
      }
      else {
         prepareResponse(response);
      }
   }


   return mav;
}

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[技术笔记] 【杭州校区】SpringMVC源码剖析1——执行流程

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