springMvc源码

protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
        if (this.handlerMappings != null) {
          //遍历所有的handlerMapping，这里的handlemapping就是初始化阶段构造的三个
            for (HandlerMapping hm : this.handlerMappings) {
                if (logger.isTraceEnabled()) {
                    logger.trace(
                            "Testing handler map [" + hm + "] in DispatcherServlet with name ‘" + getServletName() + "‘");
                }
              //这里调用具体的handler，哪个handler能够处理就直接返回
                HandlerExecutionChain handler = hm.getHandler(request);
                if (handler != null) {
                    return handler;
                }
            }
        }
        return null;
    }

public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
//1. 调用具体的实现去获取handler
   Object handler = getHandlerInternal(request);
//如果为空使用默认的
   if (handler == null) {
      handler = getDefaultHandler();
   }
//没有默认的返回空
   if (handler == null) {
      return null;
   }
   // 尝试通过BeanName去获取handler
   if (handler instanceof String) {
      String handlerName = (String) handler;
      handler = obtainApplicationContext().getBean(handlerName);
   }
//2. 获取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;
}

protected Object getHandlerInternal(HttpServletRequest request) throws Exception {
//截取url
   String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
//根据url寻找handler
   Object handler = lookupHandler(lookupPath, request);
   if (handler == null) {
      // 如果请求路径为/则使用RootHandler
      Object rawHandler = null;
      if ("/".equals(lookupPath)) {
         rawHandler = getRootHandler();
      }
      if (rawHandler == null) {
//使用默认
         rawHandler = getDefaultHandler();
      }
      if (rawHandler != null) {
         // 根据beanName尝试获取Handler
         if (rawHandler instanceof String) {
            String handlerName = (String) rawHandler;
            rawHandler = obtainApplicationContext().getBean(handlerName);
         }//校验
         validateHandler(rawHandler, request);
         handler = buildPathExposingHandler(rawHandler, lookupPath, lookupPath, null);
      }
   }
   if (handler != null && logger.isDebugEnabled()) {
      logger.debug("Mapping [" + lookupPath + "] to " + handler);
   }
   else if (handler == null && logger.isTraceEnabled()) {
      logger.trace("No handler mapping found for [" + lookupPath + "]");
   }
   return handler;
}


protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {
   // 直接根据url匹配
   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);
//封装执行链
      return buildPathExposingHandler(handler, urlPath, urlPath, null);
   }

   // 正则匹配
   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 them
      Map<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;
}

protected Object buildPathExposingHandler(Object rawHandler, String bestMatchingPattern,
      String pathWithinMapping, @Nullable Map<String, String> uriTemplateVariables) {

   HandlerExecutionChain chain = new HandlerExecutionChain(rawHandler);
   chain.addInterceptor(new PathExposingHandlerInterceptor(bestMatchingPattern, pathWithinMapping));
   if (!CollectionUtils.isEmpty(uriTemplateVariables)) {
      chain.addInterceptor(new UriTemplateVariablesHandlerInterceptor(uriTemplateVariables));
   }
   return chain;
}

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 + "]");
         }
         //不同的handlerAdapter的判断方法不同
         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");
}
以SimpleControllerHandlerAdapter为例，判断是否实现Controller接口
public boolean supports(Object handler) {
   return (handler instanceof Controller);
}

public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
      throws Exception {

   return ((Controller) handler).handleRequest(request, response);
}
public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response)
      throws Exception {

   if (HttpMethod.OPTIONS.matches(request.getMethod())) {
      response.setHeader("Allow", getAllowHeader());
      return null;
   }

   // Delegate to WebContentGenerator for checking and preparing.
   checkRequest(request);
   prepareResponse(response);

   // 如果需要同步session
   if (this.synchronizeOnSession) {
      HttpSession session = request.getSession(false);
      if (session != null) {
         Object mutex = WebUtils.getSessionMutex(session);
         synchronized (mutex) {
            return handleRequestInternal(request, response);
         }
      }
   }
调用Controller方法
   return handleRequestInternal(request, response);
}

private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
      @Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv,
      @Nullable Exception exception) throws Exception {

   boolean errorView = false;
//是否包含异常信息
   if (exception != null) {
      if (exception instanceof ModelAndViewDefiningException) {
         logger.debug("ModelAndViewDefiningException encountered", exception);
         mv = ((ModelAndViewDefiningException) exception).getModelAndView();
      }
      else {//异常视图处理
         Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
         mv = processHandlerException(request, response, handler, exception);
         errorView = (mv != null);
      }
   }

        if (mv != null && !mv.wasCleared()) {
         // 页面跳转处理
            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);
        }
    } 

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) {
      //1.解析视图名
      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());
      }//2.跳转
      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;
   }
}

protected View resolveViewName(String viewName, @Nullable Map<String, Object> model,
      Locale locale, HttpServletRequest request) throws Exception {

   if (this.viewResolvers != null) {
      for (ViewResolver viewResolver : this.viewResolvers) {
         View view = viewResolver.resolveViewName(viewName, locale);
         if (view != null) {
            return view;
         }
      }
   }
   return null;
}

public void render(Map<String, ?> model, HttpServletRequest request, HttpServletResponse response) throws Exception {
       this.renderFragment(this.markupSelectors, model, request, response);
   }

   protected void renderFragment(Set<String> markupSelectorsToRender, Map<String, ?> model, HttpServletRequest request, HttpServletResponse response) throws Exception {
       ServletContext servletContext = this.getServletContext();
       String viewTemplateName = this.getTemplateName();
       ISpringTemplateEngine viewTemplateEngine = this.getTemplateEngine();
       if (viewTemplateName == null) {
           throw new IllegalArgumentException("Property ‘templateName‘ is required");
       } else if (this.getLocale() == null) {
           throw new IllegalArgumentException("Property ‘locale‘ is required");
       } else if (viewTemplateEngine == null) {
           throw new IllegalArgumentException("Property ‘templateEngine‘ is required");
       } else {
           Map<String, Object> mergedModel = new HashMap(30);
           Map<String, Object> templateStaticVariables = this.getStaticVariables();
           if (templateStaticVariables != null) {
               mergedModel.putAll(templateStaticVariables);
           }

           if (pathVariablesSelector != null) {
               Map<String, Object> pathVars = (Map)request.getAttribute(pathVariablesSelector);
               if (pathVars != null) {
                   mergedModel.putAll(pathVars);
               }
           }

           if (model != null) {
               mergedModel.putAll(model);
           }

           ApplicationContext applicationContext = this.getApplicationContext();
           RequestContext requestContext = new RequestContext(request, response, this.getServletContext(), mergedModel);
           SpringWebMvcThymeleafRequestContext thymeleafRequestContext = new SpringWebMvcThymeleafRequestContext(requestContext, request);
           addRequestContextAsVariable(mergedModel, "springRequestContext", requestContext);
           addRequestContextAsVariable(mergedModel, "springMacroRequestContext", requestContext);
           mergedModel.put("thymeleafRequestContext", thymeleafRequestContext);
           ConversionService conversionService = (ConversionService)request.getAttribute(ConversionService.class.getName());
           ThymeleafEvaluationContext evaluationContext = new ThymeleafEvaluationContext(applicationContext, conversionService);
           mergedModel.put("thymeleaf::EvaluationContext", evaluationContext);
           IEngineConfiguration configuration = viewTemplateEngine.getConfiguration();
           WebExpressionContext context = new WebExpressionContext(configuration, request, response, servletContext, this.getLocale(), mergedModel);
           String templateName;
           Set markupSelectors;
           if (!viewTemplateName.contains("::")) {
               templateName = viewTemplateName;
               markupSelectors = null;
           } else {
               IStandardExpressionParser parser = StandardExpressions.getExpressionParser(configuration);

               FragmentExpression fragmentExpression;
               try {
                   fragmentExpression = (FragmentExpression)parser.parseExpression(context, "~{" + viewTemplateName + "}");
               } catch (TemplateProcessingException var24) {
                   throw new IllegalArgumentException("Invalid template name specification: ‘" + viewTemplateName + "‘");
               }

               ExecutedFragmentExpression fragment = FragmentExpression.createExecutedFragmentExpression(context, fragmentExpression);
               templateName = FragmentExpression.resolveTemplateName(fragment);
               markupSelectors = FragmentExpression.resolveFragments(fragment);
               Map<String, Object> nameFragmentParameters = fragment.getFragmentParameters();
               if (nameFragmentParameters != null) {
                   if (fragment.hasSyntheticParameters()) {
                       throw new IllegalArgumentException("Parameters in a view specification must be named (non-synthetic): ‘" + viewTemplateName + "‘");
                   }

                   context.setVariables(nameFragmentParameters);
               }
           }

           String templateContentType = this.getContentType();
           Locale templateLocale = this.getLocale();
           String templateCharacterEncoding = this.getCharacterEncoding();
           Set processMarkupSelectors;
           if (markupSelectors != null && markupSelectors.size() > 0) {
               if (markupSelectorsToRender != null && markupSelectorsToRender.size() > 0) {
                   throw new IllegalArgumentException("A markup selector has been specified (" + Arrays.asList(markupSelectors) + ") for a view that was already being executed as a fragment (" + Arrays.asList(markupSelectorsToRender) + "). Only one fragment selection is allowed.");
               }

               processMarkupSelectors = markupSelectors;
           } else if (markupSelectorsToRender != null && markupSelectorsToRender.size() > 0) {
               processMarkupSelectors = markupSelectorsToRender;
           } else {
               processMarkupSelectors = null;
           }

           response.setLocale(templateLocale);
           if (!this.getForceContentType()) {
               String computedContentType = SpringContentTypeUtils.computeViewContentType(request, templateContentType != null ? templateContentType : "text/html;charset=ISO-8859-1", templateCharacterEncoding != null ? Charset.forName(templateCharacterEncoding) : null);
               response.setContentType(computedContentType);
           } else {
               if (templateContentType != null) {
                   response.setContentType(templateContentType);
               } else {
                   response.setContentType("text/html;charset=ISO-8859-1");
               }

               if (templateCharacterEncoding != null) {
                   response.setCharacterEncoding(templateCharacterEncoding);
               }
           }

           viewTemplateEngine.process(templateName, processMarkupSelectors, context, response.getWriter());
       }
   }

    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;
    }