在《Servlet 3.0集成Spring MVC》中，提到創(chuàng)建DispatcherServlet并配置其處理的請(qǐng)求路徑，當(dāng)在瀏覽器發(fā)起對(duì)接口的請(qǐng)求后，如果請(qǐng)求路徑由DispatcherServlet處理，會(huì)執(zhí)行其doService方法，關(guān)注doDispatch方法

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.
        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("org.springframework.web.servlet")) {
                    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());

        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 {
                processedRequest = checkMultipart(request);
                multipartRequestParsed = (processedRequest != request);

                // Determine handler for the current request.
                // 根據(jù)當(dāng)前請(qǐng)求推斷出合適的HandlerExecutionChain
                mappedHandler = getHandler(processedRequest);
                if (mappedHandler == null || mappedHandler.getHandler() == null) {
                    noHandlerFound(processedRequest, response);
                    return;
                }

                // Determine handler adapter for the current request.
                // 根據(jù)handler推斷出合適的Handler適配器
                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;
                    }
                }
                // 執(zhí)行攔截器
                if (!mappedHandler.applyPreHandle(processedRequest, response)) {
                    return;
                }
                // 調(diào)用handler的method
                // Actually invoke the handler.
                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);
                }
            }
        }
    }

• doDispatch第一步先看獲取HandlerExecutionChain的過(guò)程

DispatcherServlet
    protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
        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;
    }

關(guān)于handlerMappings的初始化在前一篇《Spring MVC源碼筆記 一》中已經(jīng)記錄過(guò)，for循環(huán)到handlerMappings內(nèi)的RequestMappingHandlerMapping時(shí)，調(diào)用其getHandler方法，該方法繼承自基類AbstractHandlerMapping。

RequestMappingHandlerMapping關(guān)系圖

AbstractHandlerMapping
    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 = getApplicationContext().getBean(handlerName);
        }

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

在方法getHandlerInternal內(nèi)獲取到了對(duì)應(yīng)的handler，該方法在基類AbstractHandlerMethodMapping中

AbstractHandlerMethodMapping
    @Override
    protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
        String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
        if (logger.isDebugEnabled()) {
            logger.debug("Looking up handler method for path " + lookupPath);
        }
        this.mappingRegistry.acquireReadLock();
        try {
            HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
            if (logger.isDebugEnabled()) {
                if (handlerMethod != null) {
                    logger.debug("Returning handler method [" + handlerMethod + "]");
                }
                else {
                    logger.debug("Did not find handler method for [" + lookupPath + "]");
                }
            }
            return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
        }
        finally {
            this.mappingRegistry.releaseReadLock();
        }
    }
...
    protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
        List<Match> matches = new ArrayList<Match>();
        List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
        if (directPathMatches != null) {
            addMatchingMappings(directPathMatches, matches, request);
        }
        if (matches.isEmpty()) {
            // No choice but to go through all mappings...
            addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
        }

        if (!matches.isEmpty()) {
            Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
            Collections.sort(matches, comparator);
            if (logger.isTraceEnabled()) {
                logger.trace("Found " + matches.size() + " matching mapping(s) for [" +
                        lookupPath + "] : " + matches);
            }
            Match bestMatch = matches.get(0);
            if (matches.size() > 1) {
                if (CorsUtils.isPreFlightRequest(request)) {
                    return PREFLIGHT_AMBIGUOUS_MATCH;
                }
                Match secondBestMatch = matches.get(1);
                if (comparator.compare(bestMatch, secondBestMatch) == 0) {
                    Method m1 = bestMatch.handlerMethod.getMethod();
                    Method m2 = secondBestMatch.handlerMethod.getMethod();
                    throw new IllegalStateException("Ambiguous handler methods mapped for HTTP path '" +
                            request.getRequestURL() + "': {" + m1 + ", " + m2 + "}");
                }
            }
            handleMatch(bestMatch.mapping, lookupPath, request);
            return bestMatch.handlerMethod;
        }
        else {
            return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request);
        }
    }

lookupPath為請(qǐng)求的路徑，在lookupHandlerMethod方法內(nèi)，根據(jù)lookupPath從mappingRegistry中匹配到了對(duì)應(yīng)的mapping，關(guān)于loopupPath的初始化，在《Spring MVC @EnableWebMvc源碼筆記》中已經(jīng)記錄過(guò)。一般情況下只會(huì)拿到一個(gè)mapping，實(shí)際拿到的是RequestMappingInfo。然后在addMatchingMappings方法中

    private void addMatchingMappings(Collection<T> mappings, List<Match> matches, HttpServletRequest request) {
        for (T mapping : mappings) {
            T match = getMatchingMapping(mapping, request);
            if (match != null) {
                matches.add(new Match(match, this.mappingRegistry.getMappings().get(mapping)));
            }
        }
    }

在基類RequestMappingInfoHandlerMapping的getMatchingMapping方法中

RequestMappingInfoHandlerMapping
    @Override
    protected RequestMappingInfo getMatchingMapping(RequestMappingInfo info, HttpServletRequest request) {
        return info.getMatchingCondition(request);
    }

調(diào)用RequestMappingInfo的getMatchingCondition

RequestMappingInfo
    @Override
    public RequestMappingInfo getMatchingCondition(HttpServletRequest request) {
        RequestMethodsRequestCondition methods = this.methodsCondition.getMatchingCondition(request);
        ParamsRequestCondition params = this.paramsCondition.getMatchingCondition(request);
        HeadersRequestCondition headers = this.headersCondition.getMatchingCondition(request);
        ConsumesRequestCondition consumes = this.consumesCondition.getMatchingCondition(request);
        ProducesRequestCondition produces = this.producesCondition.getMatchingCondition(request);

        if (methods == null || params == null || headers == null || consumes == null || produces == null) {
            return null;
        }

        PatternsRequestCondition patterns = this.patternsCondition.getMatchingCondition(request);
        if (patterns == null) {
            return null;
        }

        RequestConditionHolder custom = this.customConditionHolder.getMatchingCondition(request);
        if (custom == null) {
            return null;
        }

        return new RequestMappingInfo(this.name, patterns,
                methods, params, headers, consumes, produces, custom.getCondition());
    }

從當(dāng)前RequestMappingInfo內(nèi)的屬性中，根據(jù)傳入的request構(gòu)造新的RequestMappingInfo返回。

• 回到AbstractHandlerMethodMapping的addMatchingMappings方法中，拿到構(gòu)造的RequestMappingInfo，即mapping后，從內(nèi)部類mappingRegistry的mappingLookup中，獲取到對(duì)應(yīng)的HandlerMethod，關(guān)于mappingLookup的初始化在《Spring MVC @EnableWebMvc源碼筆記》已經(jīng)記錄過(guò)。然后構(gòu)造新的Match，保存在matches變量中。回到AbstractHandlerMethodMapping的lookupHandlerMethod，從matches變量中取得Match后，返回了獲取到的HandlerMethod?；氐?code>AbstractHandlerMethodMapping的getHandlerInternal方法中，從容器中獲取到HandlerMethod對(duì)應(yīng)的bean之后，繼續(xù)返回。 回到AbstractHandlerMapping的getHandler方法中，拿到HandlerMethod后，進(jìn)入getHandlerExecutionChain方法

AbstractHandlerMapping
    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;
    }

可以看到，先根據(jù)HandlerMethod構(gòu)造了HandlerExecutionChain，然后獲取了所有的攔截器，根據(jù)攔截器處理的路徑與當(dāng)前請(qǐng)求的路徑做匹配，將選中的攔截器添加到HandlerExecutionChain中，返回HandlerExecutionChain，最終在AbstractHandlerMapping的getHandler中返回了這個(gè)HandlerExecutionChain。

• doDispatch第二步 回到DispatcherServlet的doDispatch方法中，關(guān)注其getHandlerAdapter方法

DispatcherServlet
    protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {
        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");
    }

handlerAdapters中保存了幾個(gè)內(nèi)置的適配器，支持當(dāng)前HandlerExecutionChain的適配器為RequestMappingHandlerAdapter，返回的也是這個(gè)適配器。

• doDispatch第三步 在mappedHandler.applyPreHandle中，執(zhí)行的是當(dāng)前HandlerExecutionChain的applyPreHandle方法

HandlerExecutionChain
    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;
    }

可以看到這里獲取了HandlerExecutionChain上的所有攔截器，然后依次執(zhí)行它們的preHandle方法。SpringMvc中配置的攔截器的工作原理就是這里。

• doDispatch最后一步執(zhí)行的ha.handle為適配器的handle方法，最終會(huì)執(zhí)行RequestMappingHandlerAdapter的handleInternal方法，關(guān)注handleInternal內(nèi)的invokeHandlerMethod

RequestMappingHandlerAdapter
    @Override
    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...
            mav = invokeHandlerMethod(request, response, handlerMethod);
        }

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

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

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

在invokeHandlerMethod內(nèi)，createInvocableHandlerMethod方法根據(jù)當(dāng)前的HandlerMethod創(chuàng)建ServletInvocableHandlerMethod，設(shè)置了需要的屬性后，調(diào)用其invokeAndHandle方法

ServletInvocableHandlerMethod
    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);
        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;
        }
    }

隨后調(diào)用了ServletInvocableHandlerMethod父類InvocableHandlerMethod的invokeForRequest方法

InvocableHandlerMethod
    public Object invokeForRequest(NativeWebRequest request, 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;
    }
...
    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);
            }
        }
    }

getMethodArgumentValues用來(lái)處理當(dāng)前請(qǐng)求的參數(shù)，在后續(xù)篇章記錄。在doInvoke方法中，getBridgedMethod().invoke(getBean(), args)，getBridgedMethod()獲取到Method,getBean()獲取到當(dāng)前的HandlerMethod在容器中對(duì)應(yīng)的bean，利用反射執(zhí)行方法。
回到InvocableHandlerMethod的invokeForRequest中，返回方法執(zhí)行的結(jié)果。對(duì)執(zhí)行結(jié)果和請(qǐng)求參數(shù)的處理將在下一篇文章中記錄。

總結(jié)：

• 瀏覽器發(fā)起請(qǐng)求，DispatcherServlet的doService方法負(fù)責(zé)處理請(qǐng)求，主要處理過(guò)程在doDispatch中
• doDispatch第一步根據(jù)當(dāng)前的請(qǐng)求獲取對(duì)應(yīng)的HandlerExecutionChain
• getHandler方法中先調(diào)用RequestMappingHandlerMapping的getHandlerInternal方法，根據(jù)當(dāng)前請(qǐng)求的路徑從基類AbstractHandlerMethodMapping的內(nèi)部類MappingRegistry中匹配出對(duì)應(yīng)的HandlerMethod然后返回。
• getHandler方法中接著調(diào)用getHandlerExecutionChain方法，創(chuàng)建新的HandlerExecutionChain，并將配置的攔截器添加到HandlerExecutionChain上，最后返回。
• doDispatch第二步根據(jù)HandlerExecutionChain，從內(nèi)置的handler適配器中匹配合適的適配器HandlerAdapter
• doDispatch第三步執(zhí)行HandlerExecutionChain上的攔截器的攔截方法
• doDispatch第四步執(zhí)行適配器HandlerAdapter的handle方法
• handle方法調(diào)用到RequestMappingHandlerAdapter內(nèi)的invokeHandlerMethod方法，根據(jù)HandlerMethod創(chuàng)建對(duì)象ServletInvocableHandlerMethod，然后執(zhí)行其invokeAndHandle方法
• 最終在ServletInvocableHandlerMethod的父類InvocableHandlerMethod的doInvoke方法中，利用反射完成了方法的執(zhí)行（即controller上method的執(zhí)行）