Struts2源码阅读(六)_ActionProxy&ActionInvocation

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<String, Object> 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<String, Object> 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<String, Object> 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<InterceptorMapping> interceptorList = new ArrayList<InterceptorMapping>(proxy.getConfig().getInterceptors());     
25.     interceptors = interceptorList.iterator();     
26. }     
27.          
28. protected void createAction(Map<String, Object> 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<String, Object> 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<String, Object> 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<InterceptorMapping> interceptorList = new ArrayList<InterceptorMapping>(proxy.getConfig().getInterceptors()); interceptors = interceptorList.iterator(); } protected void createAction(Map<String, Object> 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<String, Object> 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<String, ResultConfig> 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<String, Object> 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<String, String> params = resultConfig.getParams();          
76.         if (params != null) {                                           
77.             for (Map.Entry<String, String> 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<param></param>      
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<String, ResultConfig> 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<String, Object> 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<String, String> params = resultConfig.getParams(); if (params != null) { for (Map.Entry<String, String> paramEntry : params.entrySet()) { try { //reflectionProvider参见OgnlReflectionProvider； //resultConfig.getParams()就是result配置文件里所配置的参数<param></param> //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