下面开始讲一下主菜ActionProxy了.在这之前最好先去了解一下动态Proxy的基本知识.
ActionProxy是Action的一个代理类，也就是说Action的调用是通过ActionProxy实现的，其实就是调用了ActionProxy.execute()方法，而该方法又调用了ActionInvocation.invoke()方法。归根到底，最后调用的是DefaultActionInvocation.invokeAction()方法。
DefaultActionInvocation()->init()->createAction()。
最后通过调用ActionProxy.exute()-->ActionInvocation.invoke()-->Intercepter.intercept()-->ActionInvocation.invokeActionOnly()-->invokeAction()
这里的步骤是先由ActionProxyFactory创建ActionInvocation和ActionProxy.

 

 
  1. public ActionProxy createActionProxy(String namespace, String actionName, String methodName, Map extraContext, boolean executeResult, boolean cleanupContext) {     
  2.          
  3.     ActionInvocation inv = new DefaultActionInvocation(extraContext, true);     
  4.     container.inject(inv);     
  5.     return createActionProxy(inv, namespace, actionName, methodName, executeResult, cleanupContext);     
  6. }    

public ActionProxy createActionProxy(String namespace, String actionName, String methodName, Map extraContext, boolean executeResult, boolean cleanupContext) { ActionInvocation inv = new DefaultActionInvocation(extraContext, true); container.inject(inv); return createActionProxy(inv, namespace, actionName, methodName, executeResult, cleanupContext); }

 

 下面先看DefaultActionInvocation的init方法

 

 
  1. public void init(ActionProxy proxy) {     
  2.     this.proxy = proxy;     
  3.     Map contextMap = createContextMap();     
  4.     
  5.     // Setting this so that other classes, like object factories, can use the ActionProxy and other      
  6.     // contextual information to operate      
  7.     ActionContext actionContext = ActionContext.getContext();     
  8.     
  9.     if (actionContext != null) {     
  10.         actionContext.setActionInvocation(this);     
  11.     }     
  12.     //创建Action,struts2中每一个Request都会创建一个新的Action      
  13.     createAction(contextMap);     
  14.     
  15.     if (pushAction) {     
  16.         stack.push(action);     
  17.         contextMap.put("action", action);     
  18.     }     
  19.     
  20.     invocationContext = new ActionContext(contextMap);     
  21.     invocationContext.setName(proxy.getActionName());     
  22.     
  23.     // get a new List so we don't get problems with the iterator if someone changes the list      
  24.     List interceptorList = new ArrayList(proxy.getConfig().getInterceptors());     
  25.     interceptors = interceptorList.iterator();     
  26. }     
  27.          
  28. protected void createAction(Map contextMap) {     
  29.     // load action      
  30.     String timerKey = "actionCreate: " + proxy.getActionName();     
  31.     try {     
  32.         UtilTimerStack.push(timerKey);     
  33.         //默认为SpringObjectFactory:struts.objectFactory=spring.这里非常巧妙,在struts.properties中可以重写这个属性      
  34.         //在前面BeanSelectionProvider中通过配置文件为ObjectFactory设置实现类      
  35.         //这里以Spring为例,这里会调到SpringObjectFactory的buildBean方法,可以通过ApplicationContext的getBean()方法得到Spring的Bean      
  36.         action = objectFactory.buildAction(proxy.getActionName(), proxy.getNamespace(), proxy.getConfig(), contextMap);     
  37.     } catch (InstantiationException e) {     
  38.         throw new XWorkException("Unable to intantiate Action!", e, proxy.getConfig());     
  39.     } catch (IllegalAccessException e) {     
  40.         throw new XWorkException("Illegal access to constructor, is it public?", e, proxy.getConfig());     
  41.     } catch (Exception e) {     
  42.        ...     
  43.     } finally {     
  44.         UtilTimerStack.pop(timerKey);     
  45.     }     
  46.     
  47.     if (actionEventListener != null) {     
  48.         action = actionEventListener.prepare(action, stack);     
  49.     }     
  50. }     
  51. //SpringObjectFactory      
  52. public Object buildBean(String beanName, Map extraContext, boolean injectInternal) throws Exception {     
  53.     Object o = null;     
  54.     try {     
  55.         //SpringObjectFactory会通过web.xml中的context-param:contextConfigLocation自动注入ClassPathXmlApplicationContext      
  56.         o = appContext.getBean(beanName);     
  57.     } catch (NoSuchBeanDefinitionException e) {     
  58.         Class beanClazz = getClassInstance(beanName);     
  59.         o = buildBean(beanClazz, extraContext);     
  60.     }     
  61.     if (injectInternal) {     
  62.         injectInternalBeans(o);     
  63.     }     
  64.     return o;     
  65. }    

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,struts2中每一个Request都会创建一个新的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); //默认为SpringObjectFactory:struts.objectFactory=spring.这里非常巧妙,在struts.properties中可以重写这个属性 //在前面BeanSelectionProvider中通过配置文件为ObjectFactory设置实现类 //这里以Spring为例,这里会调到SpringObjectFactory的buildBean方法,可以通过ApplicationContext的getBean()方法得到Spring的Bean action = objectFactory.buildAction(proxy.getActionName(), proxy.getNamespace(), proxy.getConfig(), contextMap); } catch (InstantiationException e) { throw new XWorkException("Unable to intantiate Action!", e, proxy.getConfig()); } catch (IllegalAccessException e) { throw new XWorkException("Illegal access to constructor, is it public?", e, proxy.getConfig()); } catch (Exception e) { ... } finally { UtilTimerStack.pop(timerKey); } if (actionEventListener != null) { action = actionEventListener.prepare(action, stack); } } //SpringObjectFactory public Object buildBean(String beanName, Map extraContext, boolean injectInternal) throws Exception { Object o = null; try { //SpringObjectFactory会通过web.xml中的context-param:contextConfigLocation自动注入ClassPathXmlApplicationContext o = appContext.getBean(beanName); } catch (NoSuchBeanDefinitionException e) { Class beanClazz = getClassInstance(beanName); o = buildBean(beanClazz, extraContext); } if (injectInternal) { injectInternalBeans(o); } return o; }

 

 

 
  1. //接下来看看DefaultActionInvocation 的invoke方法      
  2. public String invoke() throws Exception {     
  3.     String profileKey = "invoke: ";     
  4.     try {     
  5.         UtilTimerStack.push(profileKey);     
  6.         
  7.         if (executed) {     
  8.             throw new IllegalStateException("Action has already executed");     
  9.         }     
  10.         //递归执行interceptor      
  11.         if (interceptors.hasNext()) {     
  12.             //interceptors是InterceptorMapping实际上是像一个像FilterChain一样的Interceptor链      
  13.             //通过调用Invocation.invoke()实现递归牡循环      
  14.             final InterceptorMapping interceptor = (InterceptorMapping) interceptors.next();     
  15.             String interceptorMsg = "interceptor: " + interceptor.getName();     
  16.             UtilTimerStack.push(interceptorMsg);     
  17.             try {       
  18.                  //在每个Interceptor的方法中都会return invocation.invoke()             
  19.                  resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.this);     
  20.                 }     
  21.             finally {     
  22.                 UtilTimerStack.pop(interceptorMsg);     
  23.             }     
  24.         } else {       
  25.             //当所有interceptor都执行完,最后执行Action,invokeActionOnly会调用invokeAction()方法      
  26.             resultCode = invokeActionOnly();     
  27.         }     
  28.     
  29.         // this is needed because the result will be executed, then control will return to the Interceptor, which will      
  30.         // return above and flow through again        
  31.         //在Result返回之前调用preResultListeners       
  32.         //通过executed控制,只执行一次       
  33.         if (!executed) {     
  34.             if (preResultListeners != null) {      
  35.                 for (Object preResultListener : preResultListeners) {      
  36.                     PreResultListener listener = (PreResultListener) preResultListener;     
  37.                                                                      
  38.                     String _profileKey = "preResultListener: ";      
  39.                     try {                                            
  40.                         UtilTimerStack.push(_profileKey);                                  
  41.                         listener.beforeResult(this, resultCode);     
  42.                     }                                                
  43.                     finally {                                        
  44.                         UtilTimerStack.pop(_profileKey);             
  45.                     }                                                
  46.                 }                                                    
  47.             }                                                        
  48.                                                                      
  49.             // now execute the result, if we're supposed to           
  50.             //执行Result                                              
  51.             if (proxy.getExecuteResult()) {                          
  52.                 executeResult();                                     
  53.             }                                                        
  54.                                                                      
  55.             executed = true;                                         
  56.         }                                                            
  57.                                                                      
  58.         return resultCode;                                           
  59.     }                                                                
  60.     finally {                                                        
  61.         UtilTimerStack.pop(profileKey);                              
  62.     }                                                                
  63. }      
  64.     
  65. //invokeAction      
  66. protected String invokeAction(Object action,ActionConfig actionConfig)throws Exception{     
  67.     String methodName = proxy.getMethod();     
  68.     
  69.     String timerKey = "invokeAction: " + proxy.getActionName();     
  70.     try {     
  71.         UtilTimerStack.push(timerKey);     
  72.     
  73.         boolean methodCalled = false;     
  74.         Object methodResult = null;     
  75.         Method method = null;     
  76.         try {     
  77.             //java反射机制得到要执行的方法      
  78.             method = getAction().getClass().getMethod(methodName, new Class[0]);     
  79.         } catch (NoSuchMethodException e) {     
  80.             // hmm -- OK, try doXxx instead      
  81.             //如果没有对应的方法，则使用do+Xxxx来再次获得方法         
  82.             try {     
  83.                 String altMethodName = "do" + methodName.substring(0, 1).toUpperCase() + methodName.substring(1);     
  84.                 method = getAction().getClass().getMethod(altMethodName, new Class[0]);     
  85.             } catch (NoSuchMethodException e1) {     
  86.                 // well, give the unknown handler a shot      
  87.                 if (unknownHandlerManager.hasUnknownHandlers()) {     
  88.                     try {     
  89.                         methodResult = unknownHandlerManager.handleUnknownMethod(action, methodName);     
  90.                         methodCalled = true;     
  91.                     } catch (NoSuchMethodException e2) {     
  92.                         // throw the original one      
  93.                         throw e;     
  94.                     }     
  95.                 } else {     
  96.                     throw e;     
  97.                 }     
  98.             }     
  99.         }     
  100.         //执行Method      
  101.         if (!methodCalled) {     
  102.             methodResult = method.invoke(action, new Object[0]);     
  103.         }     
  104.         //从这里可以看出可以Action的方法可以返回String去匹配Result,也可以直接返回Result类      
  105.         if (methodResult instanceof Result) {     
  106.             this.explicitResult = (Result) methodResult;     
  107.     
  108.             // Wire the result automatically      
  109.             container.inject(explicitResult);     
  110.             return null;     
  111.         } else {     
  112.             return (String) methodResult;     
  113.         }     
  114.     } catch (NoSuchMethodException e) {     
  115.         throw new IllegalArgumentException("The " + methodName + "() is not defined in action " + getAction().getClass() + "");     
  116.     } catch (InvocationTargetException e) {     
  117.         // We try to return the source exception.      
  118.         Throwable t = e.getTargetException();     
  119.     
  120.         if (actionEventListener != null) {     
  121.             String result = actionEventListener.handleException(t, getStack());     
  122.             if (result != null) {     
  123.                 return result;     
  124.             }     
  125.         }     
  126.         if (t instanceof Exception) {     
  127.             throw (Exception) t;     
  128.         } else {     
  129.             throw e;     
  130.         }     
  131.     } finally {     
  132.         UtilTimerStack.pop(timerKey);     
  133.     }     
  134. }    

//接下来看看DefaultActionInvocation 的invoke方法 public String invoke() throws Exception { String profileKey = "invoke: "; try { UtilTimerStack.push(profileKey); if (executed) { throw new IllegalStateException("Action has already executed"); } //递归执行interceptor if (interceptors.hasNext()) { //interceptors是InterceptorMapping实际上是像一个像FilterChain一样的Interceptor链 //通过调用Invocation.invoke()实现递归牡循环 final InterceptorMapping interceptor = (InterceptorMapping) interceptors.next(); String interceptorMsg = "interceptor: " + interceptor.getName(); UtilTimerStack.push(interceptorMsg); try { //在每个Interceptor的方法中都会return invocation.invoke() resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.this); } finally { UtilTimerStack.pop(interceptorMsg); } } else { //当所有interceptor都执行完,最后执行Action,invokeActionOnly会调用invokeAction()方法 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 //在Result返回之前调用preResultListeners //通过executed控制,只执行一次 if (!executed) { if (preResultListeners != null) { for (Object preResultListener : preResultListeners) { PreResultListener listener = (PreResultListener) preResultListener; String _profileKey = "preResultListener: "; try { UtilTimerStack.push(_profileKey); listener.beforeResult(this, resultCode); } finally { UtilTimerStack.pop(_profileKey); } } } // now execute the result, if we're supposed to //执行Result if (proxy.getExecuteResult()) { executeResult(); } executed = true; } return resultCode; } finally { UtilTimerStack.pop(profileKey); } } //invokeAction 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 { //java反射机制得到要执行的方法 method = getAction().getClass().getMethod(methodName, new Class[0]); } catch (NoSuchMethodException e) { // hmm -- OK, try doXxx instead //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 (unknownHandlerManager.hasUnknownHandlers()) { try { methodResult = unknownHandlerManager.handleUnknownMethod(action, methodName); methodCalled = true; } catch (NoSuchMethodException e2) { // throw the original one throw e; } } else { throw e; } } } //执行Method if (!methodCalled) { methodResult = method.invoke(action, new Object[0]); } //从这里可以看出可以Action的方法可以返回String去匹配Result,也可以直接返回Result类 if (methodResult instanceof Result) { this.explicitResult = (Result) methodResult; // Wire the result automatically container.inject(explicitResult); 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); } }

 

action执行完了，还要根据ResultConfig返回到view，也就是在invoke方法中调用executeResult方法。

 

 
  1. private void executeResult() throws Exception {     
  2.     //根据ResultConfig创建Result       
  3.     result = createResult();     
  4.     
  5.     String timerKey = "executeResult: " + getResultCode();     
  6.     try {     
  7.         UtilTimerStack.push(timerKey);     
  8.         if (result != null) {     
  9.         //开始执行Result,      
  10.         //可以参考Result的实现，如用了比较多的ServletDispatcherResult,ServletActionRedirectResult,ServletRedirectResult       
  11.             result.execute(this);     
  12.         } else if (resultCode != null && !Action.NONE.equals(resultCode)) {     
  13.             throw new ConfigurationException("No result defined for action " + getAction().getClass().getName()     
  14.                     + " and result " + getResultCode(), proxy.getConfig());     
  15.         } else {     
  16.             if (LOG.isDebugEnabled()) {     
  17.                 LOG.debug("No result returned for action " + getAction().getClass().getName() + " at " + proxy.getConfig().getLocation());     
  18.             }     
  19.         }     
  20.     } finally {     
  21.         UtilTimerStack.pop(timerKey);     
  22.     }     
  23. }               
  24.     
  25. public Result createResult() throws Exception {     
  26.     //如果Action中直接返回的Result类型,在invokeAction()保存在explicitResult      
  27.     if (explicitResult != null) {                                
  28.         Result ret = explicitResult;                             
  29.         explicitResult = null;                                   
  30.                                                                  
  31.         return ret;                                              
  32.     }     
  33.     //返回的是String则从config中得到当前Action的Results列表      
  34.     ActionConfig config = proxy.getConfig();                     
  35.     Map results = config.getResults();     
  36.                                                                  
  37.     ResultConfig resultConfig = null;                            
  38.                                                                  
  39.     synchronized (config) {                                      
  40.         try {      
  41.             //通过返回的String来匹配resultConfig        
  42.             resultConfig = results.get(resultCode);              
  43.         } catch (NullPointerException e) {                       
  44.             // swallow                                            
  45.         }                                                        
  46.         if (resultConfig == null) {                              
  47.             // If no result is found for the given resultCode, try to get a wildcard '*' match.      
  48.             //如果找不到对应name的ResultConfig，则使用name为*的Result        
  49.             //说明可以用*通配所有的Result                                    
  50.             resultConfig = results.get("*");     
  51.         }                                        
  52.     }                                            
  53.                                                  
  54.     if (resultConfig != null) {                  
  55.         try {     
  56.             //创建Result       
  57.             return objectFactory.buildResult(resultConfig, invocationContext.getContextMap());     
  58.         } catch (Exception e) {     
  59.             LOG.error("There was an exception while instantiating the result of type " + resultConfig.getClassName(), e);     
  60.             throw new XWorkException(e, resultConfig);     
  61.         }      
  62.     } else if (resultCode != null && !Action.NONE.equals(resultCode) && unknownHandlerManager.hasUnknownHandlers()) {     
  63.         return unknownHandlerManager.handleUnknownResult(invocationContext, proxy.getActionName(), proxy.getConfig(), resultCode);     
  64.     }                
  65.     return null;     
  66. }        
  67.     
  68. public Result buildResult(ResultConfig resultConfig, Map extraContext) throws Exception {     
  69.     String resultClassName = resultConfig.getClassName();     
  70.     Result result = null;                                     
  71.                                                               
  72.     if (resultClassName != null) {     
  73.         //buildBean中会用反射机制Class.newInstance来创建bean       
  74.         result = (Result) buildBean(resultClassName, extraContext);     
  75.         Map params = resultConfig.getParams();          
  76.         if (params != null) {                                           
  77.             for (Map.Entry paramEntry : params.entrySet()) {     
  78.                 try {     
  79.                      //reflectionProvider参见OgnlReflectionProvider；      
  80.               //resultConfig.getParams()就是result配置文件里所配置的参数       
  81.                      //setProperties方法最终调用的是Ognl类的setValue方法         
  82.               //这句其实就是把param名值设置到根对象result上      
  83.                     reflectionProvider.setProperty(paramEntry.getKey(), paramEntry.getValue(), result, extraContext, true);     
  84.                 } catch (ReflectionException ex) {      
  85.                     if (LOG.isErrorEnabled())           
  86.                         LOG.error("Unable to set parameter [#0] in result of type [#1]", ex,     
  87.                                 paramEntry.getKey(), resultConfig.getClassName());     
  88.                     if (result instanceof ReflectionExceptionHandler) {                
  89.                         ((ReflectionExceptionHandler) result).handle(ex);              
  90.                     }     
  91.                 }         
  92.             }             
  93.         }                 
  94.     }                     
  95.                           
  96.     return result;        
  97. }   

private void executeResult() throws Exception { //根据ResultConfig创建Result result = createResult(); String timerKey = "executeResult: " + getResultCode(); try { UtilTimerStack.push(timerKey); if (result != null) { //开始执行Result, //可以参考Result的实现，如用了比较多的ServletDispatcherResult,ServletActionRedirectResult,ServletRedirectResult result.execute(this); } else if (resultCode != null && !Action.NONE.equals(resultCode)) { throw new ConfigurationException("No result defined for action " + getAction().getClass().getName() + " and result " + getResultCode(), proxy.getConfig()); } else { if (LOG.isDebugEnabled()) { LOG.debug("No result returned for action " + getAction().getClass().getName() + " at " + proxy.getConfig().getLocation()); } } } finally { UtilTimerStack.pop(timerKey); } } public Result createResult() throws Exception { //如果Action中直接返回的Result类型,在invokeAction()保存在explicitResult if (explicitResult != null) { Result ret = explicitResult; explicitResult = null; return ret; } //返回的是String则从config中得到当前Action的Results列表 ActionConfig config = proxy.getConfig(); Map results = config.getResults(); ResultConfig resultConfig = null; synchronized (config) { try { //通过返回的String来匹配resultConfig resultConfig = results.get(resultCode); } catch (NullPointerException e) { // swallow } if (resultConfig == null) { // If no result is found for the given resultCode, try to get a wildcard '*' match. //如果找不到对应name的ResultConfig，则使用name为*的Result //说明可以用*通配所有的Result resultConfig = results.get("*"); } } if (resultConfig != null) { try { //创建Result return objectFactory.buildResult(resultConfig, invocationContext.getContextMap()); } catch (Exception e) { LOG.error("There was an exception while instantiating the result of type " + resultConfig.getClassName(), e); throw new XWorkException(e, resultConfig); } } else if (resultCode != null && !Action.NONE.equals(resultCode) && unknownHandlerManager.hasUnknownHandlers()) { return unknownHandlerManager.handleUnknownResult(invocationContext, proxy.getActionName(), proxy.getConfig(), resultCode); } return null; } public Result buildResult(ResultConfig resultConfig, Map extraContext) throws Exception { String resultClassName = resultConfig.getClassName(); Result result = null; if (resultClassName != null) { //buildBean中会用反射机制Class.newInstance来创建bean result = (Result) buildBean(resultClassName, extraContext); Map params = resultConfig.getParams(); if (params != null) { for (Map.Entry paramEntry : params.entrySet()) { try { //reflectionProvider参见OgnlReflectionProvider； //resultConfig.getParams()就是result配置文件里所配置的参数 //setProperties方法最终调用的是Ognl类的setValue方法 //这句其实就是把param名值设置到根对象result上 reflectionProvider.setProperty(paramEntry.getKey(), paramEntry.getValue(), result, extraContext, true); } catch (ReflectionException ex) { if (LOG.isErrorEnabled()) LOG.error("Unable to set parameter [#0] in result of type [#1]", ex, paramEntry.getKey(), resultConfig.getClassName()); if (result instanceof ReflectionExceptionHandler) { ((ReflectionExceptionHandler) result).handle(ex); } } } } } return result; }

 

最后看一张在网上看到的一个调用流程图作为参考：

Come From:http://qidaoxp.javaeye.com/blog/503015