Struts2源码分析--请求处理续二

接下来看看DefaultActionInvocation 的invoke方法。
 

 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);
     }
 }

 //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");
         }
             //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);
     }
 }

    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);
        }
    }

    //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");
            }
                //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);
        }
    }

看程序中的if(interceptors.hasNext())语句，当然，interceptors里存储的是interceptorMapping列表（它包括一个Interceptor和一个name），所有的截拦器必须实现Interceptor的intercept方法，而该方法的参数恰恰又是ActionInvocation，在intercept方法中还是调用invocation.invoke()，从而实现了一个Interceptor链的调用。当所有的Interceptor执行完，最后调用invokeActionOnly方法来执行Action相应的方法。
 

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);
    }
}

    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);
        }
    }

    好了，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) {
             //这儿正式执行:)
             //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 {
     if (explicitResult != null) {
         Result ret = explicitResult;
         explicitResult = null;;
         return ret;
     }
     ActionConfig config = proxy.getConfig();
     Map results = config.getResults();
     ResultConfig resultConfig = null;
     synchronized (config) {
         try {
             //根据result名称获得ResultConfig，resultCode就是result的name
             resultConfig = (ResultConfig) results.get(resultCode);
         } catch (NullPointerException e) {
         }
         if (resultConfig == null) {
             //如果找不到对应name的ResultConfig，则使用name为*的Result
             resultConfig = (ResultConfig) results.get("*");
         }
     }
     if (resultConfig != null) {
         try {
             //参照StrutsObjectFactory的代码
             Result result = objectFactory.buildResult(resultConfig, invocationContext.getContextMap());
             return result;
         } 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) && unknownHandler != null) {
         return unknownHandler.handleUnknownResult(invocationContext, proxy.getActionName(), proxy.getConfig(), resultCode);
     }
     return null;
 }
 //StrutsObjectFactory
 public Result buildResult(ResultConfig resultConfig, Map extraContext) throws Exception {
     String resultClassName = resultConfig.getClassName();
     if (resultClassName == null)
         return null;
     //创建Result，因为Result是有状态的，所以每次请求都新建一个
     Object result = buildBean(resultClassName, extraContext);
     //这句很重要，后面将会谈到，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.setProperties(resultConfig.getParams(), result, extraContext);
     if (result instanceof Result)
         return (Result) result;
     throw new ConfigurationException(result.getClass().getName() + " does not implement Result.");
 }

   private void executeResult() throws Exception {
        //根据ResultConfig创建Result
        result = createResult();
        String timerKey = "executeResult: "+getResultCode();
        try {
            UtilTimerStack.push(timerKey);
            if (result != null) {
                //这儿正式执行:)
                //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 {
        if (explicitResult != null) {
            Result ret = explicitResult;
            explicitResult = null;;
            return ret;
        }
        ActionConfig config = proxy.getConfig();
        Map results = config.getResults();
        ResultConfig resultConfig = null;
        synchronized (config) {
            try {
                //根据result名称获得ResultConfig，resultCode就是result的name
                resultConfig = (ResultConfig) results.get(resultCode);
            } catch (NullPointerException e) {
            }
            if (resultConfig == null) {
                //如果找不到对应name的ResultConfig，则使用name为*的Result
                resultConfig = (ResultConfig) results.get("*");
            }
        }
        if (resultConfig != null) {
            try {
                //参照StrutsObjectFactory的代码
                Result result = objectFactory.buildResult(resultConfig, invocationContext.getContextMap());
                return result;
            } 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) && unknownHandler != null) {
            return unknownHandler.handleUnknownResult(invocationContext, proxy.getActionName(), proxy.getConfig(), resultCode);
        }
        return null;
    }
    //StrutsObjectFactory
    public Result buildResult(ResultConfig resultConfig, Map extraContext) throws Exception {
        String resultClassName = resultConfig.getClassName();
        if (resultClassName == null)
            return null;
        //创建Result，因为Result是有状态的，所以每次请求都新建一个
        Object result = buildBean(resultClassName, extraContext);
        //这句很重要，后面将会谈到，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.setProperties(resultConfig.getParams(), result, extraContext);
        if (result instanceof Result)
            return (Result) result;
        throw new ConfigurationException(result.getClass().getName() + " does not implement Result.");
    }

   这样，一个Struts2的请求流程基本上就结束了。