SpringMVC源碼分析
我們根據工作機制中三部分來分析SpringMVC的源代碼。
其一,ApplicationContext初始化時建立所有url和Controller類的對應關系(用Map保存);
其二,根據請求url找到對應的Controller,并從Controller中找到處理請求的方法;反射調用方法，返回數據和視圖，渲染視圖和攔截器鏈處理
分為7步
1.檢查是否文件上傳
2.根據handlerMapping獲取handler執行鏈，包含handler和攔截器數組
3.根據handler找到HandlerAdapter
4.執行攔截器鏈的前處理
5.調用handlerAdapter處理handler的方法，返回數據和視圖
6.攔截器鏈后處理
7.渲染視圖和攔截器鏈最終處理
入口類為ApplicationObjectSupport的setApplicationContext方法.
setApplicationContext方法中核心部分就是初始化容器initApplicationContext(context),
子類AbstractDetectingUrlHandlerMapping實現了該方法,所以我們直接看子類中的初始化容器方法。
public abstract class ApplicationObjectSupport implements ApplicationContextAware {@Overridepublic final void setApplicationContext(@Nullable ApplicationContext context) throws BeansException {if (context == null && !isContextRequired()) {// Reset internal context state.this.applicationContext = null;this.messageSourceAccessor = null;}else if (this.applicationContext == null) {// Initialize with passed-in context.if (!requiredContextClass().isInstance(context)) {throw new ApplicationContextException("Invalid application context: needs to be of type [" + requiredContextClass().getName() + "]");}this.applicationContext = context;this.messageSourceAccessor = new MessageSourceAccessor(context);initApplicationContext(context);}else {// Ignore reinitialization if same context passed in.if (this.applicationContext != context) {throw new ApplicationContextException("Cannot reinitialize with different application context: current one is [" +this.applicationContext + "], passed-in one is [" + context + "]");}}}protected void initApplicationContext(ApplicationContext context) throws BeansException {initApplicationContext();}/*** Subclasses can override this for custom initialization behavior.*/protected void initApplicationContext() throws BeansException {}AbstractDetectingUrlHandlerMapping
@Overridepublic void initApplicationContext() throws ApplicationContextException {super.initApplicationContext();detectHandlers();}protected void detectHandlers() throws BeansException {ApplicationContext applicationContext = obtainApplicationContext();if (logger.isDebugEnabled()) {logger.debug("Looking for URL mappings in application context: " + applicationContext);}String[] beanNames = (this.detectHandlersInAncestorContexts ?BeanFactoryUtils.beanNamesForTypeIncludingAncestors(applicationContext, Object.class) :applicationContext.getBeanNamesForType(Object.class));// Take any bean name that we can determine URLs for.for (String beanName : beanNames) {String[] urls = determineUrlsForHandler(beanName);if (!ObjectUtils.isEmpty(urls)) {// URL paths found: Let's consider it a handler.registerHandler(urls, beanName);}else {if (logger.isDebugEnabled()) {logger.debug("Rejected bean name '" + beanName + "': no URL paths identified");}}}}protected abstract String[] determineUrlsForHandler(String beanName);
determineUrlsForHandler(StringbeanName)方法的作用是獲取每個Controller中的url,不同的子類有不同的實現,這是一個典型的模板設計模式.因為開發中我們用的最多的就是用注解來配置Controller中的url,BeanNameUrlHandlerMapping是AbstractDetectingUrlHandlerMapping的子類,處理注解形式的url映射.所以我們這里以BeanNameUrlHandlerMapping來進行分析.我們看BeanNameUrlHandlerMapping是如何查beanName上所有映射的url.
/*** Checks name and aliases of the given bean for URLs, starting with "/".*/@Overrideprotected String[] determineUrlsForHandler(String beanName) {List<String> urls = new ArrayList<>();if (beanName.startsWith("/")) {urls.add(beanName);}String[] aliases = obtainApplicationContext().getAliases(beanName);for (String alias : aliases) {if (alias.startsWith("/")) {urls.add(alias);}}return StringUtils.toStringArray(urls);}
Spring mvc，AbstractUrlHandlerMapping
protected void registerHandler(String[] urlPaths, String beanName) throws BeansException, IllegalStateException {Assert.notNull(urlPaths, "URL path array must not be null");for (String urlPath : urlPaths) {registerHandler(urlPath, beanName);}}protected void registerHandler(String urlPath, Object handler) throws BeansException, IllegalStateException {Assert.notNull(urlPath, "URL path must not be null");Assert.notNull(handler, "Handler object must not be null");Object resolvedHandler = handler;// Eagerly resolve handler if referencing singleton via name.if (!this.lazyInitHandlers && handler instanceof String) {String handlerName = (String) handler;ApplicationContext applicationContext = obtainApplicationContext();if (applicationContext.isSingleton(handlerName)) {resolvedHandler = applicationContext.getBean(handlerName);}}Object mappedHandler = this.handlerMap.get(urlPath);if (mappedHandler != null) {if (mappedHandler != resolvedHandler) {throw new IllegalStateException("Cannot map " + getHandlerDescription(handler) + " to URL path [" + urlPath +"]: There is already " + getHandlerDescription(mappedHandler) + " mapped.");}}else {if (urlPath.equals("/")) {if (logger.isInfoEnabled()) {logger.info("Root mapping to " + getHandlerDescription(handler));}setRootHandler(resolvedHandler);}else if (urlPath.equals("/*")) {if (logger.isInfoEnabled()) {logger.info("Default mapping to " + getHandlerDescription(handler));}setDefaultHandler(resolvedHandler);}else {this.handlerMap.put(urlPath, resolvedHandler);if (logger.isInfoEnabled()) {logger.info("Mapped URL path [" + urlPath + "] onto " + getHandlerDescription(handler));}}}}
FrameworkServlet重寫了service方法
/*** Override the parent class implementation in order to intercept PATCH requests.*/@Overrideprotected void service(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {HttpMethod httpMethod = HttpMethod.resolve(request.getMethod());//freemarker頁面if (httpMethod == HttpMethod.PATCH || httpMethod == null) {processRequest(request, response);}//前后端分離else {super.service(request, response);}}protected final void processRequest(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {long startTime = System.currentTimeMillis();Throwable failureCause = null;LocaleContext previousLocaleContext = LocaleContextHolder.getLocaleContext();LocaleContext localeContext = buildLocaleContext(request);RequestAttributes previousAttributes = RequestContextHolder.getRequestAttributes();ServletRequestAttributes requestAttributes = buildRequestAttributes(request, response, previousAttributes);WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);asyncManager.registerCallableInterceptor(FrameworkServlet.class.getName(), new RequestBindingInterceptor());initContextHolders(request, localeContext, requestAttributes);try {doService(request, response);}catch (ServletException | IOException ex) {failureCause = ex;throw ex;}catch (Throwable ex) {failureCause = ex;throw new NestedServletException("Request processing failed", ex);}finally {resetContextHolders(request, previousLocaleContext, previousAttributes);if (requestAttributes != null) {requestAttributes.requestCompleted();}if (logger.isDebugEnabled()) {if (failureCause != null) {this.logger.debug("Could not complete request", failureCause);}else {if (asyncManager.isConcurrentHandlingStarted()) {logger.debug("Leaving response open for concurrent processing");}else {this.logger.debug("Successfully completed request");}}}publishRequestHandledEvent(request, response, startTime, failureCause);}}protected abstract void doService(HttpServletRequest request, HttpServletResponse response)throws Exception;
doService模板方法
DispatcherServlet
@Overrideprotected 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);}}}}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 {//1.檢查是否文件上傳processedRequest = checkMultipart(request);multipartRequestParsed = (processedRequest != request);//2.根據handlerMapping獲取handler執行鏈，包含handler和攔截器數組// Determine handler for the current request.mappedHandler = getHandler(processedRequest);if (mappedHandler == null) {noHandlerFound(processedRequest, response);return;}//3. 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 (logger.isDebugEnabled()) {logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);}if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {return;}}//4.執行攔截器鏈的前處理if (!mappedHandler.applyPreHandle(processedRequest, response)) {return;}//5.調用handlerAdapter處理handler的方法，返回數據和視圖// Actually invoke the handler.mv = ha.handle(processedRequest, response, mappedHandler.getHandler());if (asyncManager.isConcurrentHandlingStarted()) {return;}applyDefaultViewName(processedRequest, mv);//6.攔截器鏈后處理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);}//7.渲染視圖和攔截器鏈最終處理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 afterCompletionif (mappedHandler != null) {mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);}}else {// Clean up any resources used by a multipart request.if (multipartRequestParsed) {cleanupMultipart(processedRequest);}}}}2.根據handlerMapping獲取handler執行鏈，包含handler和攔截器數組
遍歷handlerMapping，獲取handler執行鏈，包含handler（controller）和interceptor數組
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {if (this.handlerMappings != null) {for (HandlerMapping hm : this.handlerMappings) {if (logger.isTraceEnabled()) {logger.trace("Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'");}HandlerExecutionChain handler = hm.getHandler(request);if (handler != null) {return handler;}}}return null;}
java spring mvc、AbstractHandlerMapping
@Override@Nullablepublic 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;}protected abstract Object getHandlerInternal(HttpServletRequest request) throws Exception;/*** Build a {@link HandlerExecutionChain} for the given handler, including* applicable interceptors.*/protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?(HandlerExecutionChain) handler : new HandlerExecutionChain(handler));String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);for (HandlerInterceptor interceptor : this.adaptedInterceptors) {if (interceptor instanceof MappedInterceptor) {MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) {chain.addInterceptor(mappedInterceptor.getInterceptor());}}else {chain.addInterceptor(interceptor);}}return chain;}
AbstractUrlHandlerMapping從第一步ApplicationContext初始化建立的handlerMap中查詢handler
protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {// Direct match?Object handler = this.handlerMap.get(urlPath);if (handler != null) {// Bean name or resolved handler?if (handler instanceof String) {String handlerName = (String) handler;handler = obtainApplicationContext().getBean(handlerName);}validateHandler(handler, request);return buildPathExposingHandler(handler, urlPath, urlPath, null);}// Pattern match?List<String> matchingPatterns = new ArrayList<>();for (String registeredPattern : this.handlerMap.keySet()) {if (getPathMatcher().match(registeredPattern, urlPath)) {matchingPatterns.add(registeredPattern);}else if (useTrailingSlashMatch()) {if (!registeredPattern.endsWith("/") && getPathMatcher().match(registeredPattern + "/", urlPath)) {matchingPatterns.add(registeredPattern +"/");}}}String bestMatch = null;Comparator<String> patternComparator = getPathMatcher().getPatternComparator(urlPath);if (!matchingPatterns.isEmpty()) {matchingPatterns.sort(patternComparator);if (logger.isDebugEnabled()) {logger.debug("Matching patterns for request [" + urlPath + "] are " + matchingPatterns);}bestMatch = matchingPatterns.get(0);}if (bestMatch != null) {handler = this.handlerMap.get(bestMatch);if (handler == null) {if (bestMatch.endsWith("/")) {handler = this.handlerMap.get(bestMatch.substring(0, bestMatch.length() - 1));}if (handler == null) {throw new IllegalStateException("Could not find handler for best pattern match [" + bestMatch + "]");}}// Bean name or resolved handler?if (handler instanceof String) {String handlerName = (String) handler;handler = obtainApplicationContext().getBean(handlerName);}validateHandler(handler, request);String pathWithinMapping = getPathMatcher().extractPathWithinPattern(bestMatch, urlPath);// There might be multiple 'best patterns', let's make sure we have the correct URI template variables// for all of themMap<String, String> uriTemplateVariables = new LinkedHashMap<>();for (String matchingPattern : matchingPatterns) {if (patternComparator.compare(bestMatch, matchingPattern) == 0) {Map<String, String> vars = getPathMatcher().extractUriTemplateVariables(matchingPattern, urlPath);Map<String, String> decodedVars = getUrlPathHelper().decodePathVariables(request, vars);uriTemplateVariables.putAll(decodedVars);}}if (logger.isDebugEnabled()) {logger.debug("URI Template variables for request [" + urlPath + "] are " + uriTemplateVariables);}return buildPathExposingHandler(handler, bestMatch, pathWithinMapping, uriTemplateVariables);}// No handler found...return null;}3.DispatcherServlet根據handler獲取handlerAdapter
protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {if (this.handlerAdapters != null) {for (HandlerAdapter ha : this.handlerAdapters) {if (logger.isTraceEnabled()) {logger.trace("Testing handler adapter [" + ha + "]");}if (ha.supports(handler)) {return ha;}}}throw new ServletException("No adapter for handler [" + handler +"]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler");}
4.執行攔截器鏈的前處理
boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {HandlerInterceptor[] interceptors = getInterceptors();if (!ObjectUtils.isEmpty(interceptors)) {for (int i = 0; i < interceptors.length; i++) {HandlerInterceptor interceptor = interceptors[i];if (!interceptor.preHandle(request, response, this.handler)) {triggerAfterCompletion(request, response, null);return false;}this.interceptorIndex = i;}}return true;}
5.調用handlerAdapter處理handler的方法，返回ModelAndView，數據和視圖
HttpRequestHandlerAdapter
@Overridepublic boolean supports(Object handler) {return (handler instanceof HttpRequestHandler);}@Override@Nullablepublic ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)throws Exception {((HttpRequestHandler) handler).handleRequest(request, response);return null;}spring mvc注解，AbstractHandlerMethodAdapter
@Override@Nullablepublic final ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)throws Exception {return handleInternal(request, response, (HandlerMethod) handler);}protected abstract ModelAndView handleInternal(HttpServletRequest request,HttpServletResponse response, HandlerMethod handlerMethod) throws Exception;
RequestMappingHandlerAdapter
@Overrideprotected 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 necessarymav = 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;}/*** Invoke the {@link RequestMapping} handler method preparing a {@link ModelAndView}* if view resolution is required.*/@Nullableprotected 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);}invocableMethod.invokeAndHandle(webRequest, mavContainer);if (asyncManager.isConcurrentHandlingStarted()) {return null;}return getModelAndView(mavContainer, modelFactory, webRequest);}finally {webRequest.requestCompleted();}}ServletInvocableHandlerMethod
/*** Invoke the method and handle the return value through one of the* configured {@link HandlerMethodReturnValueHandler}s.*/public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,Object... providedArgs) throws Exception {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;}}InvocableHandlerMethod執行請求
/*** Invoke the method after resolving its argument values in the context of the given request.*/@Nullablepublic Object invokeForRequest(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,Object... providedArgs) throws Exception {Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);if (logger.isTraceEnabled()) {logger.trace("Invoking '" + ClassUtils.getQualifiedMethodName(getMethod(), getBeanType()) +"' with arguments " + Arrays.toString(args));}Object returnValue = doInvoke(args);if (logger.isTraceEnabled()) {logger.trace("Method [" + ClassUtils.getQualifiedMethodName(getMethod(), getBeanType()) +"] returned [" + returnValue + "]");}return returnValue;}/*** Get the method argument values for the current request.*/private 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);if (args[i] != null) {continue;}if (this.argumentResolvers.supportsParameter(parameter)) {try {args[i] = this.argumentResolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);continue;}catch (Exception ex) {if (logger.isDebugEnabled()) {logger.debug(getArgumentResolutionErrorMessage("Failed to resolve", i), ex);}throw ex;}}if (args[i] == null) {throw new IllegalStateException("Could not resolve method parameter at index " +parameter.getParameterIndex() + " in " + parameter.getExecutable().toGenericString() +": " + getArgumentResolutionErrorMessage("No suitable resolver for", i));}}return args;}/*** Attempt to resolve a method parameter from the list of provided argument values.*/@Nullableprivate Object resolveProvidedArgument(MethodParameter parameter, @Nullable Object... providedArgs) {if (providedArgs == null) {return null;}for (Object providedArg : providedArgs) {if (parameter.getParameterType().isInstance(providedArg)) {return providedArg;}}return null;}/*** Invoke the handler method with the given argument values.* 用反射調用方法*/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(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);}}}SpringMVC中提供兩種Request參數到方法中參數的綁定方式:
①通過注解進行綁定,@RequestParam
②通過參數名稱進行綁定.
使用注解進行綁定,我們只要在方法參數前面聲明@RequestParam(“a”),就可以將request中參數a的值綁定到方法的該參數上.使用參數名稱進行綁定的前提是必須要獲取方法中參數的名稱,Java反射只提供了獲取方法的參數的類型,并沒有提供獲取參數名稱的方法.SpringMVC解決這個問題的方法是用asm框架讀取字節碼文件,來獲取方法的參數名稱.asm框架是一個字節碼操作框架,關于asm更多介紹可以參考它的官網.個人建議,使用注解來完成參數綁定,這樣就可以省去asm框架的讀取字節碼的操作.
spring mvc教程、5.攔截器鏈后處理
HandlerExecutionChain
/*** Apply postHandle methods of registered interceptors.*/void applyPostHandle(HttpServletRequest request, HttpServletResponse response, @Nullable ModelAndView mv)throws Exception {HandlerInterceptor[] interceptors = getInterceptors();if (!ObjectUtils.isEmpty(interceptors)) {for (int i = interceptors.length - 1; i >= 0; i--) {HandlerInterceptor interceptor = interceptors[i];interceptor.postHandle(request, response, this.handler, mv);}}}
6.渲染視圖和攔截器鏈最終處理
DispatcherServlet
/*** 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,@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()) {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 forwardreturn;}if (mappedHandler != null) {//攔截器鏈最終處理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.*/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.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());}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;}}版权声明：本站所有资料均为网友推荐收集整理而来,仅供学习和研究交流使用。
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