// 创建Dispatcher，此类是一个Delegate，它是真正完成根据url解析，读取对应Action的地方

     public   void  init(FilterConfig filterConfig)  throws  ServletException {

         try  {

             this .filterConfig  =  filterConfig;

            initLogging();

            dispatcher  =  createDispatcher(filterConfig);

            dispatcher.init();

            dispatcher.getContainer().inject( this );

             // 读取初始参数pakages，调用parse()，解析成类似/org/apache/struts2/static,/template的数组

            String param  =  filterConfig.getInitParameter( " packages " );

            String packages  =   " org.apache.struts2.static template org.apache.struts2.interceptor.debugging " ;

             if  (param  !=   null ) {

                packages  =  param  +   "   "   +  packages;

            }

             this .pathPrefixes  =  parse(packages);

        }  finally  {

            ActionContext.setContext( null );

        }

    }

     private   void  init_DefaultProperties() {

        configurationManager.addConfigurationProvider( new  DefaultPropertiesProvider());

    }

     public   void  register(ContainerBuilder builder, LocatableProperties props)

             throws  ConfigurationException {

        

        Settings defaultSettings  =   null ;

         try  {

            defaultSettings  =   new  PropertiesSettings( " org/apache/struts2/default " );

        }  catch  (Exception e) {

             throw   new  ConfigurationException( " Could not find or error in org/apache/struts2/default.properties " , e);

        }

        

        loadSettings(props, defaultSettings);

    }

     // PropertiesSettings

     // 读取org/apache/struts2/default.properties的配置信息，如果项目中需要覆盖，可以在classpath里的struts.properties里覆写

     public  PropertiesSettings(String name) {

        

        URL settingsUrl  =  ClassLoaderUtils.getResource(name  +   " .properties " , getClass());

        

         if  (settingsUrl  ==   null ) {

            LOG.debug(name  +   " .properties missing " );

            settings  =   new  LocatableProperties();

             return ;

        }

        

        settings  =   new  LocatableProperties( new  LocationImpl( null , settingsUrl.toString()));

         //  Load settings

        InputStream in  =   null ;

         try  {

            in  =  settingsUrl.openStream();

            settings.load(in);

        }  catch  (IOException e) {

             throw   new  StrutsException( " Could not load  "   +  name  +   " .properties: "   +  e, e);

        }  finally  {

             if (in  !=   null ) {

                 try  {

                    in.close();

                }  catch (IOException io) {

                    LOG.warn( " Unable to close input stream " , io);

                }

            }

        }

    }

     private   void  init_TraditionalXmlConfigurations() {

         // 首先读取web.xml中的config初始参数值

         // 如果没有配置就使用默认的"struts-default.xml,struts-plugin.xml,struts.xml"，

         // 这儿就可以看出为什么默认的配置文件必须取名为这三个名称了

         // 如果不想使用默认的名称，直接在web.xml中配置config初始参数即可

        String configPaths  =  initParams.get( " config " );

         if  (configPaths  ==   null ) {

            configPaths  =  DEFAULT_CONFIGURATION_PATHS;

        }

        String[] files  =  configPaths.split( " //s*[,]//s* " );

         // 依次解析配置文件，xwork.xml单独解析

         for  (String file : files) {

             if  (file.endsWith( " .xml " )) {

                 if  ( " xwork.xml " .equals(file)) {

                    configurationManager.addConfigurationProvider( new  XmlConfigurationProvider(file,  false ));

                }  else  {

                    configurationManager.addConfigurationProvider( new  StrutsXmlConfigurationProvider(file,  false , servletContext));

                }

            }  else  {

                 throw   new  IllegalArgumentException( " Invalid configuration file name " );

            }

        }

    }

     protected  PackageConfig addPackage(Element packageElement)  throws  ConfigurationException {

        PackageConfig.Builder newPackage  =  buildPackageContext(packageElement);

         if  (newPackage.isNeedsRefresh()) {

             return  newPackage.build();

        }

        .

        addResultTypes(newPackage, packageElement);

        loadInterceptors(newPackage, packageElement);

        loadDefaultInterceptorRef(newPackage, packageElement);

        loadDefaultClassRef(newPackage, packageElement);

        loadGlobalResults(newPackage, packageElement);

        loadGobalExceptionMappings(newPackage, packageElement);

        NodeList actionList  =  packageElement.getElementsByTagName( " action " );

         for  ( int  i  =   0 ; i  <  actionList.getLength(); i ++ ) {

            Element actionElement  =  (Element) actionList.item(i);

            addAction(actionElement, newPackage);

        }

        loadDefaultActionRef(newPackage, packageElement);

        PackageConfig cfg  =  newPackage.build();

        configuration.addPackageConfig(cfg.getName(), cfg);

         return  cfg;

    }

     private  List loadConfigurationFiles(String fileName, Element includeElement) {

        List < Document >  docs  =   new  ArrayList < Document > ();

         if  ( ! includedFileNames.contains(fileName)) {

                

                Element rootElement  =  doc.getDocumentElement();

                NodeList children  =  rootElement.getChildNodes();

                 int  childSize  =  children.getLength();

                 for  ( int  i  =   0 ; i  <  childSize; i ++ ) {

                    Node childNode  =  children.item(i);

                     if  (childNode  instanceof  Element) {

                        Element child  =  (Element) childNode;

                         final  String nodeName  =  child.getNodeName();

                         // 解析每个action配置是，对于include文件可以使用通配符*来进行配置

                         // 如Struts.xml中可配置成<include file="actions_*.xml"/>

                         if  (nodeName.equals( " include " )) {

                            String includeFileName  =  child.getAttribute( " file " );

                             if (includeFileName.indexOf( ' * ' )  !=   - 1  ) {

                                ClassPathFinder wildcardFinder  =   new  ClassPathFinder();

                                wildcardFinder.setPattern(includeFileName);

                                Vector < String >  wildcardMatches  =  wildcardFinder.findMatches();

                                 for  (String match : wildcardMatches) {

                                    docs.addAll(loadConfigurationFiles(match, child));

                                }

                            }

                             else  {

                                

                                docs.addAll(loadConfigurationFiles(includeFileName, child));    

                            }    

                    }

                }

                }

                docs.add(doc);

                loadedFileUrls.add(url.toString());

            }

        }

         return  docs;

    }

     private   void  init_CustomConfigurationProviders() {

        String configProvs  =  initParams.get( " configProviders " );

         if  (configProvs  !=   null ) {

            String[] classes  =  configProvs.split( " //s*[,]//s* " );

             for  (String cname : classes) {

                 try  {

                    Class cls  =  ClassLoaderUtils.loadClass(cname,  this .getClass());

                    ConfigurationProvider prov  =  (ConfigurationProvider)cls.newInstance();

                    configurationManager.addConfigurationProvider(prov);

                }

                

            }

        }

    }

     public   void  doFilter(ServletRequest req, ServletResponse res, FilterChain chain)  throws  IOException, ServletException {

        HttpServletRequest request  =  (HttpServletRequest) req;

        HttpServletResponse response  =  (HttpServletResponse) res;

        ServletContext servletContext  =  getServletContext();

        String timerKey  =   " FilterDispatcher_doFilter:  " ;

         try  {

            ValueStack stack  =  dispatcher.getContainer().getInstance(ValueStackFactory. class ).createValueStack();

            ActionContext ctx  =   new  ActionContext(stack.getContext());

            ActionContext.setContext(ctx);

            

            UtilTimerStack.push(timerKey);

             // 根据content type来使用不同的Request封装，可以参见Dispatcher的wrapRequest

            request  =  prepareDispatcherAndWrapRequest(request, response);

            ActionMapping mapping;

             try  {

                 // 根据url取得对应的Action的配置信息--ActionMapping，actionMapper是通过Container的inject注入的

                mapping  =  actionMapper.getMapping(request, dispatcher.getConfigurationManager());

            }  catch  (Exception ex) {

                log.error( " error getting ActionMapping " , ex);

                dispatcher.sendError(request, response, servletContext, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex);

                 return ;

            }

             // 如果找不到对应的action配置，则直接返回。比如你输入***.jsp等等

             // 这儿有个例外，就是如果path是以“/struts”开头，则到初始参数packages配置的包路径去查找对应的静态资源并输出到页面流中，当然.class文件除外。如果再没有则跳转到404

             if  (mapping  ==   null ) {

                 //  there is no action in this request, should we look for a static resource?

                String resourcePath  =  RequestUtils.getServletPath(request);

                 if  ( "" .equals(resourcePath)  &&   null   !=  request.getPathInfo()) {

                    resourcePath  =  request.getPathInfo();

                }

                 if  (serveStatic  &&  resourcePath.startsWith( " /struts " )) {

                    String name  =  resourcePath.substring( " /struts " .length());

                    findStaticResource(name, request, response);

                }  else  {

                    chain.doFilter(request, response);

                }

                 return ;

            }

             // 正式开始Action的方法了

            dispatcher.serviceAction(request, response, servletContext, mapping);

        }  finally  {

             try  {

                ActionContextCleanUp.cleanUp(req);

            }  finally  {

                UtilTimerStack.pop(timerKey);

            }

        }

    }

     public   void  serviceAction(HttpServletRequest request, HttpServletResponse response, ServletContext context,ActionMapping mapping)  throws  ServletException {

        Map < String, Object >  extraContext  =  createContextMap(request, response, mapping, context);

         //  If there was a previous value stack, then create a new copy and pass it in to be used by the new Action

        ValueStack stack  =  (ValueStack) request.getAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY);

         if  (stack  !=   null ) {

            extraContext.put(ActionContext.VALUE_STACK, valueStackFactory.createValueStack(stack));

        }

        String timerKey  =   " Handling request from Dispatcher " ;

         try  {

            UtilTimerStack.push(timerKey);

            String namespace  =  mapping.getNamespace();

            String name  =  mapping.getName();

            String method  =  mapping.getMethod();

            Configuration config  =  configurationManager.getConfiguration();

            ActionProxy proxy  =  config.getContainer().getInstance(ActionProxyFactory. class ).createActionProxy(

                    namespace, name, method, extraContext,  true ,  false );

            request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, proxy.getInvocation().getStack());

             //  if the ActionMapping says to go straight to a result, do it!

             if  (mapping.getResult()  !=   null ) {

                Result result  =  mapping.getResult();

                result.execute(proxy.getInvocation());

            }  else  {

                proxy.execute();

            }

             //  If there was a previous value stack then set it back onto the request

             if  (stack  !=   null ) {

                request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, stack);

            }

        }  catch  (ConfigurationException e) {

            LOG.error( " Could not find action or result " , e);

            sendError(request, response, context, HttpServletResponse.SC_NOT_FOUND, e);

        }  catch  (Exception e) {

            sendError(request, response, context, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e);

        }  finally  {

            UtilTimerStack.pop(timerKey);

        }

    }

     public  Map < String,Object >  createContextMap(HttpServletRequest request, HttpServletResponse response,

            ActionMapping mapping, ServletContext context) {

         //  request map wrapping the http request objects

        Map requestMap  =   new  RequestMap(request);

         //  parameters map wrapping the http parameters.  ActionMapping parameters are now handled and applied separately

        Map params  =   new  HashMap(request.getParameterMap());

         //  session map wrapping the http session

        Map session  =   new  SessionMap(request);

         //  application map wrapping the ServletContext

        Map application  =   new  ApplicationMap(context);

        Map < String,Object >  extraContext  =  createContextMap(requestMap, params, session, application, request, response, context);

        extraContext.put(ServletActionContext.ACTION_MAPPING, mapping);

         return  extraContext;

    }

     public   void  init(ActionProxy proxy) {

         this .proxy  =  proxy;

        Map contextMap  =  createContextMap();

         //  Setting this so that other classes, like object factories, can use the ActionProxy and other

         //  contextual information to operate

        ActionContext actionContext  =  ActionContext.getContext();

         if (actionContext  !=   null ) {

            actionContext.setActionInvocation( this );

        }

         // 创建Action，可Struts2里是每次请求都新建一个Action

        createAction(contextMap);

         if  (pushAction) {

            stack.push(action);

            contextMap.put( " action " , action);

        }

        invocationContext  =   new  ActionContext(contextMap);

        invocationContext.setName(proxy.getActionName());

         //  get a new List so we don't get problems with the iterator if someone changes the list

        List interceptorList  =   new  ArrayList(proxy.getConfig().getInterceptors());

        interceptors  =  interceptorList.iterator();

    }

     protected   void  createAction(Map contextMap) {

         //  load action

        String timerKey  =   " actionCreate:  " + proxy.getActionName();

         try  {

            UtilTimerStack.push(timerKey);

             // 这儿默认建立Action是StrutsObjectFactory，实际中我使用的时候都是使用Spring创建的Action，这个时候使用的是SpringObjectFactory

            action  =  objectFactory.buildAction(proxy.getActionName(), proxy.getNamespace(), proxy.getConfig(), contextMap);

        } 

        ..

        }  finally  {

            UtilTimerStack.pop(timerKey);

        }

         if  (actionEventListener  !=   null ) {

            action  =  actionEventListener.prepare(action, stack);

        }

    }

    public  String invoke()  throws  Exception {

        String profileKey  =   " invoke:  " ;

         try  {

            UtilTimerStack.push(profileKey);

            

             if  (executed) {

                 throw   new  IllegalStateException( " Action has already executed " );

            }

                 // 先执行interceptors

             if  (interceptors.hasNext()) {

                 final  InterceptorMapping interceptor  =  (InterceptorMapping) interceptors.next();

                UtilTimerStack.profile( " interceptor:  " + interceptor.getName(), 

                         new  UtilTimerStack.ProfilingBlock < String > () {

                             public  String doProfiling()  throws  Exception {

                                resultCode  =  interceptor.getInterceptor().intercept(DefaultActionInvocation. this );

                                 return   null ;

                            }

                });

            }  else  {

                         // interceptor执行完了之后执行action

                resultCode  =  invokeActionOnly();

            }

             //  this is needed because the result will be executed, then control will return to the Interceptor, which will

             //  return above and flow through again

             if  ( ! executed) {

                         // 在Result返回之前调用preResultListeners

                 if  (preResultListeners  !=   null ) {

                     for  (Iterator iterator  =  preResultListeners.iterator();

                        iterator.hasNext();) {

                        PreResultListener listener  =  (PreResultListener) iterator.next();

                        

                        String _profileKey = " preResultListener:  " ;

                         try  {

                            UtilTimerStack.push(_profileKey);

                            listener.beforeResult( this , resultCode);

                        }

                         finally  {

                            UtilTimerStack.pop(_profileKey);

                        }

                    }

                }

                 //  now execute the result, if we're supposed to

                 if  (proxy.getExecuteResult()) {

                    executeResult();

                }

                executed  =   true ;

            }

             return  resultCode;

        }

         finally  {

            UtilTimerStack.pop(profileKey);

        }

    }

     protected  String invokeAction(Object action, ActionConfig actionConfig)  throws  Exception {

        String methodName  =  proxy.getMethod();

        String timerKey  =   " invokeAction:  " + proxy.getActionName();

         try  {

            UtilTimerStack.push(timerKey);

            

             boolean  methodCalled  =   false ;

            Object methodResult  =   null ;

            Method method  =   null ;

             try  {

                 // 获得需要执行的方法

                method  =  getAction().getClass().getMethod(methodName,  new  Class[ 0 ]);

            }  catch  (NoSuchMethodException e) {

                 // 如果没有对应的方法，则使用do+Xxxx来再次获得方法

                 try  {

                    String altMethodName  =   " do "   +  methodName.substring( 0 ,  1 ).toUpperCase()  +  methodName.substring( 1 );

                    method  =  getAction().getClass().getMethod(altMethodName,  new  Class[ 0 ]);

                }  catch  (NoSuchMethodException e1) {

                     //  well, give the unknown handler a shot

                     if  (unknownHandler  !=   null ) {

                         try  {

                            methodResult  =  unknownHandler.handleUnknownActionMethod(action, methodName);

                            methodCalled  =   true ;

                        }  catch  (NoSuchMethodException e2) {

                             //  throw the original one

                             throw  e;

                        }

                    }  else  {

                         throw  e;

                    }

                }

            }

            

             if  ( ! methodCalled) {

                methodResult  =  method.invoke(action,  new  Object[ 0 ]);

            }

             // 根据不同的Result类型返回不同值

             // 如输出流Result

             if  (methodResult  instanceof  Result) {

                 this .explicitResult  =  (Result) methodResult;

                 return   null ;

            }  else  {

                 return  (String) methodResult;

            }

        }  catch  (NoSuchMethodException e) {

             throw   new  IllegalArgumentException( " The  "   +  methodName  +   " () is not defined in action  "   +  getAction().getClass()  +   "" );

        }  catch  (InvocationTargetException e) {

             //  We try to return the source exception.

            Throwable t  =  e.getTargetException();

             if  (actionEventListener  !=   null ) {

                String result  =  actionEventListener.handleException(t, getStack());

                 if  (result  !=   null ) {

                     return  result;

                }

            }

             if  (t  instanceof  Exception) {

                 throw (Exception) t;

            }  else  {

                 throw  e;

            }

        }  finally  {

            UtilTimerStack.pop(timerKey);

        }

    }