SpringMVC执行流程与源码分析

SpringMVC 执行流程

DispatcherServlet前端控制器

doService方法

doDispatch方法

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 {
         // 检测是否有文件上传
         processedRequest = checkMultipart(request);
         multipartRequestParsed = (processedRequest != request);

         // Determine handler for the current request.
         // 获取执行链 详细看下面getHandler方法
         mappedHandler = getHandler(processedRequest);
         if (mappedHandler == null) {
            noHandlerFound(processedRequest, response);
            return;
         }

         // Determine handler adapter for the current request.
         // 获取当前请求的处理程序适配器。详看getHandlerAdapter方法
         // 如果是使用实现Controller接口方式适配器则为SimpleControllerHandlerAdapter
         // 如果使用@Controller注解方式的适配则为RequestMappingHandlerAdapter
         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;
            }
         }
         // 拦截器调用
         if (!mappedHandler.applyPreHandle(processedRequest, response)) {
            return;
         }

         // Actually invoke the handler.
         // 正在调用handler 详看下面handle方法调用 返回一个modelAndView
         mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

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

         applyDefaultViewName(processedRequest, mv);
         // 拦截器调用
         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ModelAndView视图解析器 详看下面processDispatchResult方法
      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);
         }
      }
   }
}

getHandler方法

根据请求获取Handler执行链。

public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
   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 = obtainApplicationContext().getBean(handlerName);
   }

   HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
   if (CorsUtils.isCorsRequest(request)) {
      CorsConfiguration globalConfig = this.globalCorsConfigSource.getCorsConfiguration(request);
      CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
      CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
      executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
   }
   return executionChain;
}

getHandlerAdapter方法

applyPreHandle方法

boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
   // 获取所有的拦截器
   HandlerInterceptor[] interceptors = getInterceptors();
   if (!ObjectUtils.isEmpty(interceptors)) {
      for (int i = 0; i < interceptors.length; i++) {
         HandlerInterceptor interceptor = interceptors[i];
         // 拦截器调用
         if (!interceptor.preHandle(request, response, this.handler)) {
            triggerAfterCompletion(request, response, null);
            return false;
         }
         this.interceptorIndex = i;
      }
   }
   return true;
}

SimpleControllerHandlerAdapter.handle方法

这里即调用自己实现的controler类。

processDispatchResult方法

private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
      @Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv,
      @Nullable Exception exception) throws Exception {

   boolean errorView = false;

   if (exception != null) {
      if (exception instanceof ModelAndViewDefiningException) {
         logger.debug("ModelAndViewDefiningException encountered", exception);
         mv = ((ModelAndViewDefiningException) exception).getModelAndView();
      }
      else {
         Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
         mv = processHandlerException(request, response, handler, exception);
         errorView = (mv != null);
      }
   }

   // Did the handler return a view to render?
   if (mv != null && !mv.wasCleared()) {
      //开始对数据进行渲染 详细看下面render方法
      render(mv, request, response);
      if (errorView) {
         WebUtils.clearErrorRequestAttributes(request);
      }
   }
   else {
      if (logger.isDebugEnabled()) {
         logger.debug("Null ModelAndView returned to DispatcherServlet with name '" + getServletName() +
               "': assuming HandlerAdapter completed request handling");
      }
   }

   if (WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
      // Concurrent handling started during a forward
      return;
   }

   if (mappedHandler != null) {
      mappedHandler.triggerAfterCompletion(request, response, null);
   }
}

render方法

protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {
   // Determine locale for request and apply it to the response.
   Locale locale =
         (this.localeResolver != null ? this.localeResolver.resolveLocale(request) : request.getLocale());
   response.setLocale(locale);

   View view;
   String viewName = mv.getViewName();
   if (viewName != null) {
      // We need to resolve the view name.
      // 视图解析
      view = resolveViewName(viewName, mv.getModelInternal(), locale, request);
      if (view == null) {
         throw new ServletException("Could not resolve view with name '" + mv.getViewName() +
               "' in servlet with name '" + getServletName() + "'");
      }
   }
   else {
      // No need to lookup: the ModelAndView object contains the actual View object.
      view = mv.getView();
      if (view == null) {
         throw new ServletException("ModelAndView [" + mv + "] neither contains a view name nor a " +
               "View object in servlet with name '" + getServletName() + "'");
      }
   }

   // Delegate to the View object for rendering.
   if (logger.isDebugEnabled()) {
      logger.debug("Rendering view [" + view + "] in DispatcherServlet with name '" + getServletName() + "'");
   }
   try {
      if (mv.getStatus() != null) {
         response.setStatus(mv.getStatus().value());
      }
      // 将数据渲染到页面上 详看下面AbstractView.render方法
      view.render(mv.getModelInternal(), request, response);
   }
   catch (Exception ex) {
      if (logger.isDebugEnabled()) {
         logger.debug("Error rendering view [" + view + "] in DispatcherServlet with name '" +
               getServletName() + "'", ex);
      }
      throw ex;
   }
}

AbstractView.render方法

public void render(@Nullable Map<String, ?> model, HttpServletRequest request,
      HttpServletResponse response) throws Exception {

   if (logger.isTraceEnabled()) {
      logger.trace("Rendering view with name '" + this.beanName + "' with model " + model +
         " and static attributes " + this.staticAttributes);
   }

   Map<String, Object> mergedModel = createMergedOutputModel(model, request, response);
   prepareResponse(request, response);
   //渲染合并输出视图 详细看下面InternalResourceView.renderMergedOutputModel方法
   renderMergedOutputModel(mergedModel, getRequestToExpose(request), response);
}

InternalResourceView.renderMergedOutputModel方法

protected void renderMergedOutputModel(
      Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws Exception {

   // Expose the model object as request attributes.
   exposeModelAsRequestAttributes(model, request);

   // Expose helpers as request attributes, if any.
   exposeHelpers(request);

   // Determine the path for the request dispatcher.
   String dispatcherPath = prepareForRendering(request, response);

   // Obtain a RequestDispatcher for the target resource (typically a JSP).
   // 获取转发器
   RequestDispatcher rd = getRequestDispatcher(request, dispatcherPath);
   if (rd == null) {
      throw new ServletException("Could not get RequestDispatcher for [" + getUrl() +
            "]: Check that the corresponding file exists within your web application archive!");
   }

   // If already included or response already committed, perform include, else forward.
   if (useInclude(request, response)) {
      response.setContentType(getContentType());
      if (logger.isDebugEnabled()) {
         logger.debug("Including resource [" + getUrl() + "] in InternalResourceView '" + getBeanName() + "'");
      }
      rd.include(request, response);
   }

   else {
      // Note: The forwarded resource is supposed to determine the content type itself.
      if (logger.isDebugEnabled()) {
         logger.debug("Forwarding to resource [" + getUrl() + "] in InternalResourceView '" + getBeanName() + "'");
      }
      // 转发请求
      rd.forward(request, response);
   }
}

到这里即是实现了Controller接口方式的处理流程。那么接下来即是常用的@Controller注解方式的源码流程。

AbstractHandlerMethodAdapter.handle方法

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

RequestMappingHandlerAdapter.handleInternal方法

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...
      // 详看下面invokeHandlerMethod方法
      mav = invokeHandlerMethod(request, response, handlerMethod);
   }

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

   return mav;
}

invokeHandlerMethod方法

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

   ServletWebRequest webRequest = new ServletWebRequest(request, response);
   try {
      WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod);
      ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory);

      ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod);
      if (this.argumentResolvers != null) {
         invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
      }
      if (this.returnValueHandlers != null) {
         invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);
      }
      invocableMethod.setDataBinderFactory(binderFactory);
      invocableMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);

      ModelAndViewContainer mavContainer = new ModelAndViewContainer();
      mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));
      modelFactory.initModel(webRequest, mavContainer, invocableMethod);
      mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);

      AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response);
      asyncWebRequest.setTimeout(this.asyncRequestTimeout);

      WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
      asyncManager.setTaskExecutor(this.taskExecutor);
      asyncManager.setAsyncWebRequest(asyncWebRequest);
      asyncManager.registerCallableInterceptors(this.callableInterceptors);
      asyncManager.registerDeferredResultInterceptors(this.deferredResultInterceptors);

      if (asyncManager.hasConcurrentResult()) {
         Object result = asyncManager.getConcurrentResult();
         mavContainer = (ModelAndViewContainer) asyncManager.getConcurrentResultContext()[0];
         asyncManager.clearConcurrentResult();
         if (logger.isDebugEnabled()) {
            logger.debug("Found concurrent result value [" + result + "]");
         }
         invocableMethod = invocableMethod.wrapConcurrentResult(result);
      }
      // 调用和处理请求 详细看下面invokeAndHandle方法
      invocableMethod.invokeAndHandle(webRequest, mavContainer);
      if (asyncManager.isConcurrentHandlingStarted()) {
         return null;
      }

      return getModelAndView(mavContainer, modelFactory, webRequest);
   }
   finally {
      webRequest.requestCompleted();
   }
}

invokeAndHandle方法

public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,
      Object... providedArgs) throws Exception {
   // 调用请求 详看下面invokeForRequest方法
   Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
   setResponseStatus(webRequest);

   if (returnValue == null) {
      if (isRequestNotModified(webRequest) || getResponseStatus() != null || mavContainer.isRequestHandled()) {
         mavContainer.setRequestHandled(true);
         return;
      }
   }
   else if (StringUtils.hasText(getResponseStatusReason())) {
      mavContainer.setRequestHandled(true);
      return;
   }

   mavContainer.setRequestHandled(false);
   Assert.state(this.returnValueHandlers != null, "No return value handlers");
   try {
      this.returnValueHandlers.handleReturnValue(
            returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
   }
   catch (Exception ex) {
      if (logger.isTraceEnabled()) {
         logger.trace(getReturnValueHandlingErrorMessage("Error handling return value", returnValue), ex);
      }
      throw ex;
   }
}

invokeForRequest方法

public Object invokeForRequest(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception {
    // 获取请求参数 详看下面getMethodArgumentValues方法
    Object[] args = this.getMethodArgumentValues(request, mavContainer, providedArgs);
    if (this.logger.isTraceEnabled()) {
        this.logger.trace("Invoking '" + ClassUtils.getQualifiedMethodName(this.getMethod(), this.getBeanType()) + "' with arguments " + Arrays.toString(args));
    }
    // 调用请求 详看下面doInvoke方法
    Object returnValue = this.doInvoke(args);
    if (this.logger.isTraceEnabled()) {
        this.logger.trace("Method [" + ClassUtils.getQualifiedMethodName(this.getMethod(), this.getBeanType()) + "] returned [" + returnValue + "]");
    }

    return returnValue;
}

getMethodArgumentValues方法

private Object[] getMethodArgumentValues(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception {
    MethodParameter[] parameters = this.getMethodParameters();
    Object[] args = new Object[parameters.length];

    for(int i = 0; i < parameters.length; ++i) {
        MethodParameter parameter = parameters[i];
        parameter.initParameterNameDiscovery(this.parameterNameDiscoverer);
        args[i] = this.resolveProvidedArgument(parameter, providedArgs);
        if (args[i] == null) {
            if (this.argumentResolvers.supportsParameter(parameter)) {
                try {
                    args[i] = this.argumentResolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);
                } catch (Exception var9) {
                    if (this.logger.isDebugEnabled()) {
                        this.logger.debug(this.getArgumentResolutionErrorMessage("Failed to resolve", i), var9);
                    }

                    throw var9;
                }
            } else if (args[i] == null) {
                throw new IllegalStateException("Could not resolve method parameter at index " + parameter.getParameterIndex() + " in " + parameter.getExecutable().toGenericString() + ": " + this.getArgumentResolutionErrorMessage("No suitable resolver for", i));
            }
        }
    }

    return args;
}

doInvoke方法

protected Object doInvoke(Object... args) throws Exception {
    ReflectionUtils.makeAccessible(this.getBridgedMethod());

    try {
        // 这里即利用反射方式调用controller类里面的方法 getBean即Controller类的实例
        return this.getBridgedMethod().invoke(this.getBean(), args);
    } catch (IllegalArgumentException var5) {
        this.assertTargetBean(this.getBridgedMethod(), this.getBean(), args);
        String text = var5.getMessage() != null ? var5.getMessage() : "Illegal argument";
        throw new IllegalStateException(this.getInvocationErrorMessage(text, args), var5);
    } catch (InvocationTargetException var6) {
        Throwable targetException = var6.getTargetException();
        if (targetException instanceof RuntimeException) {
            throw (RuntimeException)targetException;
        } else if (targetException instanceof Error) {
            throw (Error)targetException;
        } else if (targetException instanceof Exception) {
            throw (Exception)targetException;
        } else {
            String text = this.getInvocationErrorMessage("Failed to invoke handler method", args);
            throw new IllegalStateException(text, targetException);
        }
    }
}

到这里即请求处理完成，后面的视图解析及渲染均与前面的代码一致。