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) {
					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 (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
						return;
					}
				}

				if (!mappedHandler.applyPreHandle(processedRequest, response)) {
					return;
				}

				// Actually invoke the handler. 在该方法中会进行参数的转换
				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);
				}
			}
		}
	}

@Nullable
	protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
		if (this.handlerMappings != null) {
			for (HandlerMapping mapping : this.handlerMappings) { //handlermapping中为所有初始化的controller以及对应的方法。
				HandlerExecutionChain handler = mapping.getHandler(request);
				if (handler != null) {
					return handler;
				}
			}
		}
		return null;
	}


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 (logger.isTraceEnabled()) {
			logger.trace("Mapped to " + handler);
		}
		else if (logger.isDebugEnabled() && !request.getDispatcherType().equals(DispatcherType.ASYNC)) {
			logger.debug("Mapped to " + executionChain.getHandler());
		}

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

		return executionChain;
	}

//public class InvocableHandlerMethod extends HandlerMethod 
/*获取对应方法的参数，请求方法的参数包括两类：
1、url中自带
2、session中的信息
具体的有30种类型，这些反转解析都实现了HandlerMethodArgumentResolver接口。
*/
protected Object[] getMethodArgumentValues(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
			Object... providedArgs) throws Exception {

		MethodParameter[] parameters = 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] = resolveProvidedArgument(parameter, providedArgs); //确认该参数是否为传入参数
			if (args[i] != null) {
				continue;
			}
			if (this.argumentResolvers.supportsParameter(parameter)) { //决策是否为支持参数
				try {
					args[i] = this.argumentResolvers.resolveArgument( //spring目前支持30种类型的参数。
							parameter, mavContainer, request, this.dataBinderFactory);
					continue;
				}
				catch (Exception ex) {
					// Leave stack trace for later, e.g. AbstractHandlerExceptionResolver
					if (logger.isDebugEnabled()) {
						String message = ex.getMessage();
						if (message != null && !message.contains(parameter.getExecutable().toGenericString())) {
							logger.debug(formatArgumentError(parameter, message));
						}
					}
					throw ex;
				}
			}
			if (args[i] == null) {
				throw new IllegalStateException(formatArgumentError(parameter, "No suitable resolver"));
			}
		}
		return args;
	}

//public class InvocableHandlerMethod extends HandlerMethod {
/*调用方法相对就比较简单了，直接使用代理方法调用对应的bean以及对应的参数*/
protected Object doInvoke(Object... args) throws Exception {
		ReflectionUtils.makeAccessible(getBridgedMethod());
		try {
			return getBridgedMethod().invoke(getBean(), args);
		}
		catch (IllegalArgumentException ex) {
			assertTargetBean(getBridgedMethod(), getBean(), args);
			String text = (ex.getMessage() != null ? ex.getMessage() : "Illegal argument");
			throw new IllegalStateException(formatInvokeError(text, args), ex);
		}
		catch (InvocationTargetException ex) {
			// Unwrap for HandlerExceptionResolvers ...
			Throwable targetException = ex.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 {
				throw new IllegalStateException(formatInvokeError("Invocation failure", args), targetException);
			}
		}
	}

javax.servlet.http.HttpServletRequest request