Spring MVC：DispatcherServlet源码结构

public classDispatcherServlet extendsFrameworkServlet {

002  

003    /** List of HandlerMappings used by this servlet */

004    privateList<HandlerMapping> handlerMappings;

005 

006    /** List of HandlerAdapters used by this servlet */

007    privateList<HandlerAdapter> handlerAdapters;

008 

009    /** List of ViewResolvers used by this servlet */

010    privateList<ViewResolver> viewResolvers;

011 

012    /**

013     * Exposes the DispatcherServlet-specific request attributes and delegates to {@link #doDispatch}

014     * for the actual dispatching.

015     */

016    @Override

017    protectedvoid doService(HttpServletRequest request, HttpServletResponse response) {

018        doDispatch(request, response);

019    }

020 

021    /**

022     * Process the actual dispatching to the handler.

023     * <p>The handler will be obtained by applying the servlet's HandlerMappings in order.

024     * The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters

025     * to find the first that supports the handler class.

026     * <p>All HTTP methods are handled by this method. It's up to HandlerAdapters or handlers

027     * themselves to decide which methods are acceptable.

028     * @param request current HTTP request

029     * @param response current HTTP response

030     * @throws Exception in case of any kind of processing failure

031     */

032    protectedvoid doDispatch(HttpServletRequest request, HttpServletResponse response) {

033        HttpServletRequest processedRequest = request;

034        HandlerExecutionChain mappedHandler =null;

035        ModelAndView mv;

036 

037        // Determine handler for the current request.

038        mappedHandler = getHandler(processedRequest,false);

039 

040        // Determine handler adapter for the current request.

041        HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

042 

043        // Apply preHandle methods of registered interceptors.

044        HandlerInterceptor[] interceptors = mappedHandler.getInterceptors();

045        for(int i = 0; i < interceptors.length; i++) {

046                HandlerInterceptor interceptor = interceptors[i];

047                interceptor.preHandle(processedRequest, response, mappedHandler.getHandler())

048        }

049 

050        // Actually invoke the handler.

051        mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

052 

053        // Apply postHandle methods of registered interceptors.

054        for(int i = interceptors.length - 1; i >=0; i--) {

055                HandlerInterceptor interceptor = interceptors[i];

056                interceptor.postHandle(processedRequest, response, mappedHandler.getHandler(), mv);

057        }

058 

059        // Did the handler return a view to render?

060        render(mv, processedRequest, response);

061 

062        // Trigger after-completion for successful outcome.

063        triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response,null);

064    }

065 

066  

067    /**

068     * Return the HandlerExecutionChain for this request.

069     * <p>Tries all handler mappings in order.

070     * @param request current HTTP request

071     * @return the HandlerExecutionChain, or <code>null</code> if no handler could be found

072     */

073    protectedHandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {

074        for(HandlerMapping hm : this.handlerMappings) {

075            HandlerExecutionChain handler = hm.getHandler(request);

076            if(handler != null) {

077                returnhandler;

078            }

079        }

080        returnnull;

081    }

082  

083    /**

084     * Return the HandlerAdapter for this handler object.

085     * @param handler the handler object to find an adapter for

086     * @throws ServletException if no HandlerAdapter can be found for the handler. This is a fatal error.

087     */

088    protectedHandlerAdapter getHandlerAdapter(Object handler) throwsServletException {

089        for(HandlerAdapter ha : this.handlerAdapters) {

090            if(ha.supports(handler)) {

091                returnha;

092            }

093        }

094    }

095 

096    /**

097     * Render the given ModelAndView.

098     * <p>This is the last stage in handling a request. It may involve resolving the view by name.

099     * @param mv the ModelAndView to render

100     * @param request current HTTP servlet request

101     * @param response current HTTP servlet response

102     * @throws ServletException if view is missing or cannot be resolved

103     * @throws Exception if there's a problem rendering the view

104     */

105    protectedvoid render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response)throws Exception {

106        View view;

107        view = mv.getView();

108        view.render(mv.getModelInternal(), request, response);

109    }

110}