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wucaifang819787:
你好!麻烦问下不知道哪个图片行不行的:http://dl.it ...
struts2源码浅析(四) -
ChenXzh:
高手,佩服得五体投地
关于struts2报There is no Action mapped for namespace / and action name xxx_xxx
接上一篇讲了filter后,现在request到了action内了。
//Load Action class for mapping and invoke the appropriate Action method, or go directly to the Result. public void serviceAction(HttpServletRequest request, HttpServletResponse response, ServletContext context, ActionMapping mapping) throws ServletException { //createContextMap方法主要把Application、Session、Request的key value值拷贝到Map中 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); boolean nullStack = stack == null; if (nullStack) { ActionContext ctx = ActionContext.getContext(); if (ctx != null) { stack = ctx.getValueStack(); } } 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(); //创建一个Action的代理对象,ActionProxyFactory是创建ActionProxy的工厂 //参考实现类:DefaultActionProxy和DefaultActionProxyFactory 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! //如果是Result,则直接转向,关于Result,ActionProxy,ActionInvocation下一讲中再分析 if (mapping.getResult() != null) { Result result = mapping.getResult(); result.execute(proxy.getInvocation()); } else { //执行Action proxy.execute(); } // If there was a previous value stack then set it back onto the request if (!nullStack) { request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, stack); } } catch (ConfigurationException e) { // WW-2874 Only log error if in devMode if(devMode) { LOG.error("Could not find action or result", e); } else { LOG.warn("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); } }
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.
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
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; }
执行action时,要通过一系列拦截器的拦截,这也是struts2的一大特色。
拦截器中的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。
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; }
这样,经过拦截器拦截,action调用业务code,返回result,再处理result交予前端,一个request的处理也告一段落。
附图一张,是关于action开始执行到处理返回result的整个过程。
结语:
发文数量不多,不怎么会写这样子的文章,造成了文字很少,代码很多,图也画的不甚专业,大家多多包涵。
入行时间不久,看源码难免有遗漏,错误的地方,还请大家多多指教。
评论
不知道哪个图片行不行的:http://dl.iteye.com/upload/picture/pic/129620/7557b68c-460b-393f-b427-d0f04e5f1b50.png这个地址可以看的到的,有时间麻烦看下。
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