上一篇简单介绍了spring mvc 的一些基本内容 和DispatcherServlet 的doc。这一篇将会继续写我对Spring Mvc 源代码的理解。直接上代码：
/** * This implementation calls {@link #initStrategies}. --这里实现调用 */ @Override
//这里可以跟踪进，看到最终调用这个的是在：orgapache omcatembed omcat-embed-core8.5.23 omcat-embed-core-8.5.23-sources.jar!javaxservletGenericServlet.java中的init()方法中，而 GenericServlet.java 则是实现了Servlet接口的init() protected void onRefresh(ApplicationContext context) { initStrategies(context); } /** * Initialize the strategy objects that this servlet uses. * <p>May be overridden in subclasses in order to initialize further strategy objects. */ protected void initStrategies(ApplicationContext context) {
//上传文件流 initMultipartResolver(context);
//国际化 initLocaleResolver(context);
//主题 initThemeResolver(context);
//url映射 initHandlerMappings(context);
//适配器 initHandlerAdapters(context);
//处理异常 initHandlerExceptionResolvers(context);
//视图名转换 initRequestToViewNameTranslator(context);
//视图处理器 initViewResolvers(context); initFlashMapManager(context); }
先看下匹配器 initHandlerMappings(context);
/** * Initialize the HandlerMappings used by this class. * <p>If no HandlerMapping beans are defined in the BeanFactory for this namespace, * we default to BeanNameUrlHandlerMapping. */ private void initHandlerMappings(ApplicationContext context) { this.handlerMappings = null; if (this.detectAllHandlerMappings) { //是否检索所有的HandlerMapping 映射。默认是true // Find all HandlerMappings in the ApplicationContext, including ancestor contexts.
//查询所有的映射，包括祖先context的
Map<String, HandlerMapping> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false); if (!matchingBeans.isEmpty()) { this.handlerMappings = new ArrayList<HandlerMapping>(matchingBeans.values()); // 放在一个排序的list中 AnnotationAwareOrderComparator.sort(this.handlerMappings); } } else { try { HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class); this.handlerMappings = Collections.singletonList(hm); } catch (NoSuchBeanDefinitionException ex) { // Ignore, we'll add a default HandlerMapping later. } } // Ensure we have at least one HandlerMapping, by registering // a default HandlerMapping if no other mappings are found.
// 如果没有handlerMapping ，则使用默认的handlerMapping
if (this.handlerMappings == null) { this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class); if (logger.isDebugEnabled()) { logger.debug("No HandlerMappings found in servlet '" + getServletName() + "': using default"); } } }
最终会得到一个list：List<HandlerMapping>
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下面看 initHandlerAdapters
/** * Initialize the HandlerAdapters used by this class. * <p>If no HandlerAdapter beans are defined in the BeanFactory for this namespace, * we default to SimpleControllerHandlerAdapter. */ private void initHandlerAdapters(ApplicationContext context) { this.handlerAdapters = null; if (this.detectAllHandlerAdapters) { // Find all HandlerAdapters in the ApplicationContext, including ancestor contexts. Map<String, HandlerAdapter> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerAdapter.class, true, false); if (!matchingBeans.isEmpty()) { this.handlerAdapters = new ArrayList<HandlerAdapter>(matchingBeans.values()); // We keep HandlerAdapters in sorted order. AnnotationAwareOrderComparator.sort(this.handlerAdapters); } } else { try { HandlerAdapter ha = context.getBean(HANDLER_ADAPTER_BEAN_NAME, HandlerAdapter.class); this.handlerAdapters = Collections.singletonList(ha); } catch (NoSuchBeanDefinitionException ex) { // Ignore, we'll add a default HandlerAdapter later. } } // Ensure we have at least some HandlerAdapters, by registering // default HandlerAdapters if no other adapters are found. if (this.handlerAdapters == null) { this.handlerAdapters = getDefaultStrategies(context, HandlerAdapter.class); if (logger.isDebugEnabled()) { logger.debug("No HandlerAdapters found in servlet '" + getServletName() + "': using default"); } } }
从代码可以看出，这里的代码和 initHandlerMappings 非常像，都是把bean添加到一个list里面，唯一不同的是类型而已。
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DispatcherServlet 处理请求方法，在 doService(HttpServletRequest request, HttpServletResponse response) 。在DispatcherServlet 的父类FrameworkServlet的processRequest 中调用了这个方法。（这里又是一个模板方法模式）。doService(HttpServletRequest request, HttpServletResponse response) 源代码如下：
/** * Exposes the DispatcherServlet-specific request attributes and delegates to {@link #doDispatch} * for the actual dispatching. */
//实际调用DispatcherServlet
@Override 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.
//保存一份快照，方便恢复
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(DEFAULT_STRATEGIES_PREFIX)) { attributesSnapshot.put(attrName, request.getAttribute(attrName)); } } } // Make framework objects available to handlers and view objects.
// 使处理器和视图都可以使用object
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 { doDispatch(request, response); //实际调度 } finally { if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) { // Restore the original attribute snapshot, in case of an include. if (attributesSnapshot != null) { restoreAttributesAfterInclude(request, attributesSnapshot); } } } }
/** * Process the actual dispatching to the handler. * <p>The handler will be obtained by applying the servlet's HandlerMappings in order. * The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters * to find the first that supports the handler class. * <p>All HTTP methods are handled by this method. It's up to HandlerAdapters or handlers * themselves to decide which methods are acceptable. * @param request current HTTP request * @param response current HTTP response * @throws Exception in case of any kind of processing failure */
//真正处理请求
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 {
//检查多媒体resolveer processedRequest = checkMultipart(request); multipartRequestParsed = (processedRequest != request); // Determine handler for the current request.
//查找匹配的Controller 、方法、参数、返回值、异常等消息。处理的方法是迭代 initHandlerMapping(context) 里面的注册的mapping，这个是放在一个list里面 mappedHandler = getHandler(processedRequest); if (mappedHandler == null || mappedHandler.getHandler() == null) { noHandlerFound(processedRequest, response); return; } // Determine handler adapter for the current request. HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler()); //确定请求调用的HandlerAdapter。我们自定义的HandlerAdapter，也是在这里被获取到。 // Process last-modified header, if supported by the handler. String method = request.getMethod(); //获取报文里面的方法名称 boolean isGet = "GET".equals(method); //是否是GET调用 if (isGet || "HEAD".equals(method)) { long lastModified = ha.getLastModified(request, mappedHandler.getHandler()); //查找url中对应的方法 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.
// 执行处理器
mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); if (asyncManager.isConcurrentHandlingStarted()) { return; }
//确定view applyDefaultViewName(processedRequest, mv);
//应用已注册拦截器的后期方法 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); }
//解释模型和者视图（ModelAndView），或者是异常 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); } } } }
从这里看出，基本流程就是：查到需要调用的方法--> 执行方法 --->返回模型和视图（ModelAndView）或者异常 --> 解释返回的模型和视图
ha.handle(processedRequest, response, mappedHandler.getHandler()) 的源代码如下：
@Override protected ModelAndView handleInternal(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod) throws Exception { ModelAndView mav; checkRequest(request); //检查是否是支持的http请求（GET、POST）和 需要session 支持 // Execute invokeHandlerMethod in synchronized block if required. //是否需要同步执行方法 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); //查找、执行方法，准备视图 } if (!response.containsHeader(HEADER_CACHE_CONTROL)) { if (getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) { applyCacheSeconds(response, this.cacheSecondsForSessionAttributeHandlers); } else { prepareResponse(response); } } return mav; }
/** * Invoke the {@link RequestMapping} handler method preparing a {@link ModelAndView} * if view resolution is required. * @since 4.2 * @see #createInvocableHandlerMethod(HandlerMethod) */ protected ModelAndView invokeHandlerMethod(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod) throws Exception { ServletWebRequest webRequest = new ServletWebRequest(request, response); //获取url相关 try { WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod); ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory); ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod); //获取要Controller、method、args、return type 等信息 invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers); 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); } invocableMethod.invokeAndHandle(webRequest, mavContainer); //真正地使用反射来执行方法，并返回值 if (asyncManager.isConcurrentHandlingStarted()) { return null; } return getModelAndView(mavContainer, modelFactory, webRequest); //返回ModelAndView } finally { webRequest.requestCompleted(); } }
invocableMethod.invokeAndHandle(webRequest, mavContainer) 的代码如下：
/** * Invoke the method and handle the return value through one of the * configured {@link HandlerMethodReturnValueHandler}s. * @param webRequest the current request * @param mavContainer the ModelAndViewContainer for this request * @param providedArgs "given" arguments matched by type (not resolved) */ public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception { Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs); //执行请求 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); 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; } }
/** * Invoke the method after resolving its argument values in the context of the given request. * <p>Argument values are commonly resolved through {@link HandlerMethodArgumentResolver}s. * The {@code providedArgs} parameter however may supply argument values to be used directly, * i.e. without argument resolution. Examples of provided argument values include a * {@link WebDataBinder}, a {@link SessionStatus}, or a thrown exception instance. * Provided argument values are checked before argument resolvers. * @param request the current request * @param mavContainer the ModelAndViewContainer for this request * @param providedArgs "given" arguments matched by type, not resolved * @return the raw value returned by the invoked method * @exception Exception raised if no suitable argument resolver can be found, * or if the method raised an exception */ public Object invokeForRequest(NativeWebRequest request, ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception { Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs); //获取参数 if (logger.isTraceEnabled()) { logger.trace("Invoking '" + ClassUtils.getQualifiedMethodName(getMethod(), getBeanType()) + "' with arguments " + Arrays.toString(args)); } Object returnValue = doInvoke(args); //执行方法 if (logger.isTraceEnabled()) { logger.trace("Method [" + ClassUtils.getQualifiedMethodName(getMethod(), getBeanType()) + "] returned [" + returnValue + "]"); } return returnValue; }
/** * Invoke the handler method with the given argument values. */ protected Object doInvoke(Object... args) throws Exception { ReflectionUtils.makeAccessible(getBridgedMethod()); try { return getBridgedMethod().invoke(getBean(), args); //使用反射执行方法 } catch (IllegalArgumentException ex) { assertTargetBean(getBridgedMethod(), getBean(), args); String text = (ex.getMessage() != null ? ex.getMessage() : "Illegal argument"); throw new IllegalStateException(getInvocationErrorMessage(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 { String text = getInvocationErrorMessage("Failed to invoke handler method", args); throw new IllegalStateException(text, targetException); } } }
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继续跟进 getModelAndView(mavContainer, modelFactory, webRequest) 方法，源代码如下：
private ModelAndView getModelAndView(ModelAndViewContainer mavContainer, ModelFactory modelFactory, NativeWebRequest webRequest) throws Exception { modelFactory.updateModel(webRequest, mavContainer); if (mavContainer.isRequestHandled()) { return null; } ModelMap model = mavContainer.getModel(); ModelAndView mav = new ModelAndView(mavContainer.getViewName(), model, mavContainer.getStatus()); if (!mavContainer.isViewReference()) { mav.setView((View) mavContainer.getView()); } if (model instanceof RedirectAttributes) { Map<String, ?> flashAttributes = ((RedirectAttributes) model).getFlashAttributes(); HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class); RequestContextUtils.getOutputFlashMap(request).putAll(flashAttributes); } return mav; }
ModelAndView 代码如下：
public class ModelAndView { /** View instance or view name String */ private Object view; /** Model Map */ private ModelMap model; /** Optional HTTP status for the response */ private HttpStatus status; /** Indicates whether or not this instance has been cleared with a call to {@link #clear()} */ private boolean cleared = false; //************************ 省略 }
再返回看下解释视图和模型或者异常的方法 processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException) ，源代码如下：
/** * Handle the result of handler selection and handler invocation, which is * either a ModelAndView or an Exception to be resolved to a ModelAndView. */ private void processDispatchResult(HttpServletRequest request, HttpServletResponse response, HandlerExecutionChain mappedHandler, ModelAndView mv, 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()) { render(mv, request, response); //解释、渲染视图和模型 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 the given ModelAndView. * <p>This is the last stage in handling a request. It may involve resolving the view by name. * @param mv the ModelAndView to render * @param request current HTTP servlet request * @param response current HTTP servlet response * @throws ServletException if view is missing or cannot be resolved * @throws Exception if there's a problem rendering the view */ protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception { // Determine locale for request and apply it to the response.
//国际化、本地化 Locale locale = this.localeResolver.resolveLocale(request); response.setLocale(locale); View view; if (mv.isReference()) { //引用视图 // We need to resolve the view name. view = resolveViewName(mv.getViewName(), 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(); //获取视图 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.
// 委派模式 if (logger.isDebugEnabled()) { logger.debug("Rendering view [" + view + "] in DispatcherServlet with name '" + getServletName() + "'"); } try { if (mv.getStatus() != null) { response.setStatus(mv.getStatus().value()); }
//真正渲染的方法 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; } }
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以上就是我的基本分析，当然还有很多细节没有看，只是看了基本的流程和核心代码。如果有错，请大神指正。