spring spring mvc原理

spring mvc原理

spring mvc初始化

1. spring容器初始化执行refresh()方法，走到最后一步finishRefresh()方法
2. finishRefresh()方法内部调用ApplicationListener.onApplicationEvent方法
3. spring mvc提供ContextRefreshListener类，实现ApplicationListener接口，重写onApplicationEvent方法
4. onApplicationEvent方法内部调用DispatcherServlet.initStrategies方法初始化spring mvc各组件

DispatcherServlet.initStrategies()

	protected void initStrategies(ApplicationContext context) {
		initMultipartResolver(context);
		initLocaleResolver(context);
		initThemeResolver(context);
		initHandlerMappings(context);// 映射器
		initHandlerAdapters(context);// 适配器
		initHandlerExceptionResolvers(context);
		initRequestToViewNameTranslator(context);
		initViewResolvers(context);// 视图解析器
		initFlashMapManager(context);
	}

spring mvc Controller类型

annotation类型：一个Controller类对应多个uri，由RequestMappingHandlerMapping解析
BeanName类型：一个Controller类对应一个uri，由BeanNameUrlHandlerMapping解析

spring mvc注册Controller方式

@Controller，annotation类型，由RequestMappingHandlerAdapter执行方法
implements Controller + @Component("/uri")，BeanName类型，由SimpleControllerHandlerAdapter执行方法
implements HttpRequestHandler + @Component("/uri")，BeanName类型，由HttpRequestHandlerAdapter执行方法

spring mvc处理请求

1. doDispatch()
2. checkMultipart()判断请求是否附带文件
3. getHandler()根据uri去handlerMappings找Controller（扩展点HandlerMapping）
4. getHandlerAdapter()根据Controller类型去handlerAdapters找适配器（扩展点HandlerAdapter）
5. mappedHandler.applyPreHandle()调用拦截器的preHandle方法
6. handle()执行方法并进行判断：返回、转发或者重定向
   （扩展点HandlerMethodArgumentResolver方法参数类型解析器）
   （扩展点HttpMessageConverter返回消息转换器）
   （扩展点HandlerMethodReturnValueHandler方法返回类型解析器）
7. mappedHandler.applyPostHandle()调用拦截器的postHandle方法
8. processDispatchResult()视图渲染（扩展点ViewResolver）

第六步补充
annotation类型Controller用反射执行方法
BeanName类型Controller用接口执行方法

doDispatch()

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 {
				// 检查请求是否附带文件，根据请求头属性Content-Type判断
				processedRequest = checkMultipart(request);
				multipartRequestParsed = (processedRequest != request);

				// Determine handler for the current request.
				// 从缓存中取Handler
				mappedHandler = getHandler(processedRequest);
				if (mappedHandler == null) {
					noHandlerFound(processedRequest, response);
					return;
				}

				// Determine handler adapter for the current request.
				// 根据Controller类型找适配器
				// @Controller 对应 RequestMappingHandlerAdapter
				HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

				// Process last-modified header, if supported by the handler.
				// 处理http谓词
				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;
					}
				}

				// 调用拦截器的preHandle方法
				if (!mappedHandler.applyPreHandle(processedRequest, response)) {
					return;
				}

				// Actually invoke the handler.
				// 执行Controller逻辑，并进行视图判断（重定向 or 转发 or 响应页面）
				// @ResponseBody的处理结果为null
				mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

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

				// 视图名称转换
				applyDefaultViewName(processedRequest, mv);
				// 调用拦截器的postHandle方法
				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);
			}
			// 渲染视图
			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);
				}
			}
		}
	}