DispatcherServlet类讲解

"serial"  DispatcherServlet

}

    /** MultipartResolver used by this servlet */private MultipartResolver multipartResolver; /** LocaleResolver used by this servlet */private LocaleResolver localeResolver;/** ThemeResolver used by this servlet */private ThemeResolver themeResolver;/** List of HandlerMappings used by this servlet */private List handlerMappings;   //处理器映射列表/** List of HandlerAdapters used by this servlet */private List handlerAdapters;   //处理器适配器列表/** List of HandlerExceptionResolvers used by this servlet */private List handlerExceptionResolvers; //处理器异常解析器列表/** RequestToViewNameTranslator used by this servlet */private RequestToViewNameTranslator viewNameTranslator;/** FlashMapManager used by this servlet */private FlashMapManager flashMapManager;/** List of ViewResolvers used by this servlet */private List viewResolvers; //视图解析器列表

/** * Create a new {@code DispatcherServlet} that will create its own internal web
     * application context based on defaults and values provided through servlet
     * init-params. Typically used in Servlet 2.5 or earlier environments, where the only
     * option for servlet registration is through {@code web.xml} which requires the use
     * of a no-arg constructor.
     * 
Calling {@link #setContextConfigLocation} (init-param 'contextConfigLocation')
     * will dictate which XML files will be loaded by the
     * {@linkplain #DEFAULT_CONTEXT_CLASS default XmlWebApplicationContext}
     * 
Calling {@link #setContextClass} (init-param 'contextClass') overrides the
     * default {@code XmlWebApplicationContext} and allows for specifying an alternative class,
     * such as {@code AnnotationConfigWebApplicationContext}.
     * 
Calling {@link #setContextInitializerClasses} (init-param 'contextInitializerClasses')
     * indicates which {@code ApplicationContextInitializer} classes should be used to
     * further configure the internal application context prior to refresh().
     * @see #DispatcherServlet(WebApplicationContext)
     * 
     */public DispatcherServlet() {super();
        setDispatchOptionsRequest(true);
    }

    //初始化这个DispatcherServlet使用到的策略对象。这个方法有可能会被子类覆盖。protected void initStrategies(ApplicationContext context) {        initMultipartResolver(context);
        initLocaleResolver(context);
        initThemeResolver(context);

        /* 
　　　　　 * 
         *    
         */     
        initHandlerMappings(context);

        initHandlerExceptionResolvers(context);
        initRequestToViewNameTranslator(context);
        initViewResolvers(context);
        initFlashMapManager(context);
    }

    　　  doService(HttpServletRequest request, HttpServletResponse response) = WebAsyncUtils.getAsyncManager(request).hasConcurrentResult() ? " resumed" : """DispatcherServlet with name '" + getServletName() + "'" + resumed +
                    " processing " + request.getMethod() + " request for [" + getRequestUri(request) + "]" attributesSnapshot = =  HashMap attrNames == (.cleanupAfterInclude || attrName.startsWith("org.springframework.web.servlet"=  (inputFlashMap !=  (! (attributesSnapshot !=

  doDispatch(HttpServletRequest request, HttpServletResponse response) ==  multipartRequestParsed = WebAsyncManager asyncManager == = processedRequest == (processedRequest !=mappedHandler = (mappedHandler ==  || mappedHandler.getHandler() == HandlerAdapter ha =String method = isGet = "GET" (isGet || "HEAD" lastModified ="Last-Modified value for [" + getRequestUri(request) + "] is: " + ( ServletWebRequest(request, response).checkNotModified(lastModified) && (!mv ==dispatchException =  NestedServletException("Handler dispatch failed" NestedServletException("Handler processing failed" (mappedHandler !=

  /** * Return the HandlerExecutionChain for this request.
     * 
Tries all handler mappings in order.
     * @param request current HTTP request
     * @return the HandlerExecutionChain, or {@code null} if no handler could be found     */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;
    }

 /** * Render the given ModelAndView.
     * 
This is the last stage in handling a request. It may involve resolving the view by name.
     * @param mv the ModelAndView to render
     * @param request current HTTP servlet request
     * @param response current HTTP servlet response
     * @throws ServletException if view is missing or cannot be resolved
     * @throws Exception if there's a problem rendering the view     */protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {// Determine locale for request and apply it to the response.Locale locale = this.localeResolver.resolveLocale(request);
        response.setLocale(locale);

        View view;if (mv.isReference()) {// We need to resolve the view name.view = resolveViewName(mv.getViewName(), mv.getModelInternal(), locale, request);if (view == null) {throw new ServletException("Could not resolve view with name '" + mv.getViewName() +
                        "' in servlet with name '" + getServletName() + "'");
            }
        }else {// No need to lookup: the ModelAndView object contains the actual View object.view = mv.getView();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;
        }
    }

 /** * Resolve the given view name into a View object (to be rendered).
     * 
The default implementations asks all ViewResolvers of this dispatcher.
     * Can be overridden for custom resolution strategies, potentially based on
     * specific model attributes or request parameters.
     * @param viewName the name of the view to resolve
     * @param model the model to be passed to the view
     * @param locale the current locale
     * @param request current HTTP servlet request
     * @return the View object, or {@code null} if none found
     * @throws Exception if the view cannot be resolved
     * (typically in case of problems creating an actual View object)
     * @see ViewResolver#resolveViewName     */protected View resolveViewName(String viewName, Map model, Locale locale,
            HttpServletRequest request) throws Exception {for (ViewResolver viewResolver : this.viewResolvers) {
            View view = viewResolver.resolveViewName(viewName, locale);if (view != null) {return view;
            }
        }return null;
    }