public class DispatcherServlet extends FrameworkServlet { |
002 | |
003 | /** List of HandlerMappings used by this servlet */ |
004 | private List<HandlerMapping> handlerMappings; |
005 |
006 | /** List of HandlerAdapters used by this servlet */ |
007 | private List<HandlerAdapter> handlerAdapters; |
008 |
009 | /** List of ViewResolvers used by this servlet */ |
010 | private List<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 | protected void 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 | protected void 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 | protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception { |
074 | for (HandlerMapping hm : this.handlerMappings) { |
075 | HandlerExecutionChain handler = hm.getHandler(request); |
076 | if (handler != null) { |
077 | return handler; |
078 | } |
079 | } |
080 | return null; |
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 | protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException { |
089 | for (HandlerAdapter ha : this.handlerAdapters) { |
090 | if (ha.supports(handler)) { |
091 | return ha; |
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 | protected void 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 | } |
