SpringMVC源码解析

首先上时序图，帮助理解整个解析过程和执行过程

准备

• Spring版本：5.0.8

解析过程

配置过程解析

HttpServletBean 继承 HttpServlet，在 servlet 启动时会执行其 init 方法

// HttpServletBean
public final void init() throws ServletException {
   if (logger.isDebugEnabled()) {
      logger.debug("Initializing servlet '" + getServletName() + "'");
   }

   // Set bean properties from init parameters.
   // 获取web.xml中初始化参数
   PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
   if (!pvs.isEmpty()) {
      try {
         // 使用BeanWrapper构造DispatcherServlet
         BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
         ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
         bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
         initBeanWrapper(bw);
         // 设置DispatcherServlet属性
         bw.setPropertyValues(pvs, true);
      }
      catch (BeansException ex) {
         if (logger.isErrorEnabled()) {
            logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
         }
         throw ex;
      }
   }

   // 默认空实现 子类覆盖实现
   initServletBean();

   if (logger.isDebugEnabled()) {
      logger.debug("Servlet '" + getServletName() + "' configured successfully");
   }
}

// FrameworkServlet
protected final void initServletBean() throws ServletException {
   getServletContext().log("Initializing Spring FrameworkServlet '" + getServletName() + "'");
   if (this.logger.isInfoEnabled()) {
      this.logger.info("FrameworkServlet '" + getServletName() + "': initialization started");
   }
   long startTime = System.currentTimeMillis();

   try {
      // 初始化WebApplicationContext属性
      this.webApplicationContext = initWebApplicationContext();
      initFrameworkServlet();
   }
   catch (ServletException | RuntimeException ex) {
      this.logger.error("Context initialization failed", ex);
      throw ex;
   }

   if (this.logger.isInfoEnabled()) {
      long elapsedTime = System.currentTimeMillis() - startTime;
      this.logger.info("FrameworkServlet '" + getServletName() + "': initialization completed in " +
            elapsedTime + " ms");
   }
}

// FrameworkServlet
protected WebApplicationContext initWebApplicationContext() {
   WebApplicationContext rootContext =
         WebApplicationContextUtils.getWebApplicationContext(getServletContext());
   WebApplicationContext wac = null;

   if (this.webApplicationContext != null) {
      // A context instance was injected at construction time -> use it
      wac = this.webApplicationContext;
      if (wac instanceof ConfigurableWebApplicationContext) {
         ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac;
         if (!cwac.isActive()) {
            // The context has not yet been refreshed -> provide services such as
            // setting the parent context, setting the application context id, etc
            if (cwac.getParent() == null) {
               // The context instance was injected without an explicit parent -> set
               // the root application context (if any; may be null) as the parent
               cwac.setParent(rootContext);
            }
            configureAndRefreshWebApplicationContext(cwac);
         }
      }
   }
   if (wac == null) {
      // No context instance was injected at construction time -> see if one
      // has been registered in the servlet context. If one exists, it is assumed
      // that the parent context (if any) has already been set and that the
      // user has performed any initialization such as setting the context id
      wac = findWebApplicationContext();
   }
   if (wac == null) {
      // No context instance is defined for this servlet -> create a local one
      // 创建web上下文对象
      wac = createWebApplicationContext(rootContext);
   }

   if (!this.refreshEventReceived) {
      // Either the context is not a ConfigurableApplicationContext with refresh
      // support or the context injected at construction time had already been
      // refreshed -> trigger initial onRefresh manually here.
      // 执行DispatcherServlet的实现 初始化springmvc九大组件
      onRefresh(wac);
   }

   if (this.publishContext) {
      // Publish the context as a servlet context attribute.
      String attrName = getServletContextAttributeName();
      getServletContext().setAttribute(attrName, wac);
      if (this.logger.isDebugEnabled()) {
         this.logger.debug("Published WebApplicationContext of servlet '" + getServletName() +
               "' as ServletContext attribute with name [" + attrName + "]");
      }
   }

   return wac;
}

// FrameworkServlet
protected WebApplicationContext createWebApplicationContext(@Nullable ApplicationContext parent) {
   Class<?> contextClass = getContextClass();
   if (this.logger.isDebugEnabled()) {
      this.logger.debug("Servlet with name '" + getServletName() +
            "' will try to create custom WebApplicationContext context of class '" +
            contextClass.getName() + "'" + ", using parent context [" + parent + "]");
   }
   if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
      throw new ApplicationContextException(
            "Fatal initialization error in servlet with name '" + getServletName() +
            "': custom WebApplicationContext class [" + contextClass.getName() +
            "] is not of type ConfigurableWebApplicationContext");
   }
   // 通过反射实例化web上下文对象
   ConfigurableWebApplicationContext wac =
         (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);

   wac.setEnvironment(getEnvironment());
   wac.setParent(parent);
   String configLocation = getContextConfigLocation();
   if (configLocation != null) {
      wac.setConfigLocation(configLocation);
   }
   // 配置并刷新web应用上下文
   configureAndRefreshWebApplicationContext(wac);

   return wac;
}

// FrameworkServlet
protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac) {
   if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
      // The application context id is still set to its original default value
      // -> assign a more useful id based on available information
      if (this.contextId != null) {
         wac.setId(this.contextId);
      }
      else {
         // Generate default id...
         wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
               ObjectUtils.getDisplayString(getServletContext().getContextPath()) + '/' + getServletName());
      }
   }

   wac.setServletContext(getServletContext());
   wac.setServletConfig(getServletConfig());
   wac.setNamespace(getNamespace());
   wac.addApplicationListener(new SourceFilteringListener(wac, new ContextRefreshListener()));

   // The wac environment's #initPropertySources will be called in any case when the context
   // is refreshed; do it eagerly here to ensure servlet property sources are in place for
   // use in any post-processing or initialization that occurs below prior to #refresh
   ConfigurableEnvironment env = wac.getEnvironment();
   if (env instanceof ConfigurableWebEnvironment) {
      ((ConfigurableWebEnvironment) env).initPropertySources(getServletContext(), getServletConfig());
   }

   postProcessWebApplicationContext(wac);
   applyInitializers(wac);
   // 刷新web上下文 refresh方法可查看IoC容器初始化过程
   wac.refresh();
}

回到 FrameworkServlet 的 initWebApplicationContext 方法，继续执行 onRefresh 方法

// DispatcherServlet
protected void onRefresh(ApplicationContext context) {
   initStrategies(context);
}

初始化策略，当没有配置时会读取 DispatcherServlet.properties 中配置的默认策略

// DispatcherServlet
protected void initStrategies(ApplicationContext context) {
   // 初始化文件上传处理
   initMultipartResolver(context);
   // 初始化本地化处理
   initLocaleResolver(context);
   // 初始化主题处理
   initThemeResolver(context);
   // 初始化处理器映射器(用来保存controller中配置的RequestMapping与Method对应关系)
   initHandlerMappings(context);
   // 初始化处理器适配器(用来动态匹配Method参数 包括类转换 动态赋值)
   initHandlerAdapters(context);
   // 初始化处理器异常处理
   initHandlerExceptionResolvers(context);
   // 初始化请求至视图名转换
   initRequestToViewNameTranslator(context);
   // 初始化视图解析器
   initViewResolvers(context);
   // 初始化flash映射管理器
   initFlashMapManager(context);
}

DispatcherServlet.properties

org.springframework.web.servlet.LocaleResolver=org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver

org.springframework.web.servlet.ThemeResolver=org.springframework.web.servlet.theme.FixedThemeResolver

org.springframework.web.servlet.HandlerMapping=org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,\
   org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping

org.springframework.web.servlet.HandlerAdapter=org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter,\
   org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter,\
   org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter

org.springframework.web.servlet.HandlerExceptionResolver=org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver,\
   org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver,\
   org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver

org.springframework.web.servlet.RequestToViewNameTranslator=org.springframework.web.servlet.view.DefaultRequestToViewNameTranslator

org.springframework.web.servlet.ViewResolver=org.springframework.web.servlet.view.InternalResourceViewResolver

org.springframework.web.servlet.FlashMapManager=org.springframework.web.servlet.support.SessionFlashMapManager

执行过程解析

当一个 post/get 请求进来后，会调用 FrameworkServlet 的 doPost/doGet 方法，这里以 post 请求为例

// FrameworkServlet
protected final void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {

   processRequest(request, response);
}

// FrameworkServlet
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 {
      // 执行请求
      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);
   }
}

// DispatcherServlet
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<>();
      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);
         }
      }
   }
}

// DispatcherServlet
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 {
         // 如果是MultipartContent类型则转换为MultiHttpServletRequest类型的request
         processedRequest = checkMultipart(request);
         multipartRequestParsed = (processedRequest != request);

         // 根据request寻找对应的handler
         mappedHandler = getHandler(processedRequest);
         if (mappedHandler == null) {
            noHandlerFound(processedRequest, response);
            return;
         }

         // 根据处理器获取handler适配器
         HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

         // 如果当前handler支持last-modified头处理
         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;
            }
         }

         // 拦截器postHandle方法处理
         if (!mappedHandler.applyPreHandle(processedRequest, response)) {
            return;
         }

         // Actually invoke the handler.
         // 处理器处理请求 返回结果试图对象
         mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

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

         // 结果视图对象的处理
         applyDefaultViewName(processedRequest, mv);
         // 拦截器postHandle方法处理
         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);
      }
      // 处理最终结果 渲染视图等
      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) {
            // 请求成功响应之后的方法
            mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
         }
      }
      else {
         // Clean up any resources used by a multipart request.
         if (multipartRequestParsed) {
            cleanupMultipart(processedRequest);
         }
      }
   }
}

// DispatcherServlet
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
   if (this.handlerMappings != null) {
      // handlerMappings在启动时预先注册
      for (HandlerMapping hm : this.handlerMappings) {
         if (logger.isTraceEnabled()) {
            logger.trace(
                  "Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'");
         }
         // 获取处理器执行链
         HandlerExecutionChain handler = hm.getHandler(request);
         if (handler != null) {
            return handler;
         }
      }
   }
   return null;
}

// AbstractHandlerMapping
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
   // 根据request获取handler
   Object handler = getHandlerInternal(request);
   if (handler == null) {
      // 没有查找到使用默认handler
      handler = getDefaultHandler();
   }
   if (handler == null) {
      return null;
   }
   // Bean name or resolved handler?
   // 如果handler是字符串类型 说明是bean名称 需要获取handler bean对象
   if (handler instanceof String) {
      String handlerName = (String) handler;
      handler = obtainApplicationContext().getBean(handlerName);
   }

   // 封装handler执行链
   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;
}

// AbstractHandlerMethodMapping
protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
   // 获取request中的url 用来匹配handler
   String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
   if (logger.isDebugEnabled()) {
      logger.debug("Looking up handler method for path " + lookupPath);
   }
   this.mappingRegistry.acquireReadLock();
   try {
      // 根据路径寻找handler
      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();
   }
}

// AbstractHandlerMethodMapping
protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
   List<Match> matches = new ArrayList<>();
   // 直接匹配
   List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
   // 存在匹配 则添加到匹配列表中
   if (directPathMatches != null) {
      addMatchingMappings(directPathMatches, matches, request);
   }
   // 没有匹配 遍历所有处理方法查找
   if (matches.isEmpty()) {
      // No choice but to go through all mappings...
      addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
   }

   // 存在匹配
   if (!matches.isEmpty()) {
      Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
      matches.sort(comparator);
      if (logger.isTraceEnabled()) {
         logger.trace("Found " + matches.size() + " matching mapping(s) for [" + lookupPath + "] : " + matches);
      }
      // 排序之后获取第一个
      Match bestMatch = matches.get(0);
      // 有多个匹配 会找出第二个进行比较
      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 + "}");
         }
      }
      // 设置request参数
      handleMatch(bestMatch.mapping, lookupPath, request);
      // 返回匹配的url处理方法
      return bestMatch.handlerMethod;
   }
   else {
      // 处理没有匹配情况直接返回null
      return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request);
   }
}

// AbstractHandlerMapping
protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
   // 如果当前handler不是执行链类型 则创建一个新的执行链封装
   HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
         (HandlerExecutionChain) handler : new HandlerExecutionChain(handler));

   // 当前url
   String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
   // 遍历拦截器 与当前url匹配的添加至执行链中
   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;
}

// DispatcherServlet
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()) {
      // 渲染
      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 forward
      return;
   }

   if (mappedHandler != null) {
      mappedHandler.triggerAfterCompletion(request, response, null);
   }
}

// DispatcherServlet
protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {
   // Determine locale for request and apply it to the response.
   // 设置本地化
   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.
      // 解析视图名获取视图对象
      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());
      }
      // 委托给视图进行渲染
      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;
   }
}

整个配置过程及执行过程完成。

参考资料

Spring源码深度解析
https://blog.csdn.net/a295277302/article/details/70234229
https://blog.csdn.net/heroqiang/article/details/79037456