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WebWork2源码分析续一

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至于Action是的创建则是由ActionProxy来完成的,来看一段简要的程序调用



ActionProxy proxy = ActionProxyFactory.getFactory().createActionProxy(namespace, actionName, extraContext);



request.setAttribute(ServletActionContext.WEBWORK_VALUESTACK_KEY, proxy.getInvocation().getStack());  //调用ActionInvocation



proxy.execute();



其实 ActionProxy是一个接口,而ActionProxyFactory则是一个抽象类,他们都是通过一个DefaultActionProxy和DefaultActionProxyFactory来完成操作的,且ActionProxy将调用ActionInvocation接口,由DefaultActionInvocation初始化的时候读取配置,然后由Invoke()方法来完成Action的调用及一些在Action被调用之前的Interceptor的操作.下面是关于DefaultActionInvocation的初始化和调用代码.



public class DefaultActionInvocation implements ActionInvocation {



private void init() throws Exception {



        Map contextMap = createContextMap();



        createAction();  //加载Action



        if (pushAction) {



            stack.push(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()); //获取配置



        interceptors = interceptorList.iterator();



    }




 


public String invoke() throws Exception {



        if (executed) {



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



        }



//这里是执行拦截器的操作, 注: 拦截器本身就是AOP的一个特殊实现,Servlet2.3 中Filter就是一个特例啊



        if (interceptors.hasNext()) {



            Interceptor interceptor = (Interceptor) interceptors.next();



            resultCode = interceptor.intercept(this);



        } else {



            resultCode = invokeAction(getAction(), proxy.getConfig());



        }



        // 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) {



            if (preResultListeners != null) {



                for (Iterator iterator = preResultListeners.iterator();



                     iterator.hasNext();) {



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



                    listener.beforeResult(this, resultCode);



                }



            }



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



            if (proxy.getExecuteResult()) {



                executeResult();



            }



            executed = true;



        }







}



下面再来说说Interceptor 的实现结构,刚开始我以为XWork1.x中Interceptor 应该是从Filter中继承下来的,后来看了源码,原来我的想法不对,想想也的确是不需要,也不应该从Filter下继承,因为Filter就是Servlet2.3的一个API,而XWork1.x设计目的就是要脱离Servlet API,且Interceptor的实现并非是少了Filter就不行,只是我们有了Filter将会来的更加方便!




 


对于WebWork2.x中的所有的拦截器,他们都有一个公共的接口Interceptor,在它当中定义了拦截器的一些基本操作方法,然后有一个AroundInterceptor抽象类,实现了该接口, AroundInterceptor的作用是组合拦截器的调用顺序,代码如下:



public String intercept(ActionInvocation invocation) throws Exception {



        String result = null;



        before(invocation);  //这里是用于组合调用顺序



        result = invocation.invoke();



        after(invocation, result);



        return result;



  }




 


至于将Map 中的数据转换到我们的VO中,是通过ParametersInterceptor拦截器来完成操作的,这个拦截器是一个真正的实现类,他从AroundInterceptor抽象类下面继承



public class ParametersInterceptor extends AroundInterceptor {



    //~ Methods ////////////////////////////////////////////////////////////////



    protected void after(ActionInvocation dispatcher, String result) throws Exception {



    }



    protected void before(ActionInvocation invocation) throws Exception {



        if (!(invocation.getAction() instanceof NoParameters)) {



            final Map parameters = ActionContext.getContext().getParameters();



//用于获取Map 结构中的Parameters



            if (log.isDebugEnabled()) {



                log.debug("Setting params " + parameters);



            }



            ActionContext invocationContext = invocation.getInvocationContext();



            try {



                invocationContext.put(InstantiatingNullHandler.CREATE_NULL_OBJECTS, Boolean.TRUE);



                invocationContext.put(XWorkMethodAccessor.DENY_METHOD_EXECUTION, Boolean.TRUE);



                invocationContext.put(XWorkConverter.REPORT_CONVERSION_ERRORS, Boolean.TRUE);



                if (parameters != null) {



                    final OgnlValueStack stack = ActionContext.getContext().getValueStack();



//用于获取OgnlValueStack操作,这个package没看过,具体听夏昕说是一套可读写对象属性的的类库,功能有些类似与Jakarta Commons BeanUtils ,及Spring Bean Wrapper



                    for (Iterator iterator = parameters.entrySet().iterator();



//遍历Parameters中的信息



                        iterator.hasNext();) {



                        Map.Entry entry = (Map.Entry) iterator.next();



                        String name = entry.getKey().toString();



//填充VO信息



                        if (acceptableName(name)) {



                            Object value = entry.getValue();



                            stack.setValue(name, value);



                        }



                    }



                }



            } finally {



                invocationContext.put(InstantiatingNullHandler.CREATE_NULL_OBJECTS, Boolean.FALSE);



                invocationContext.put(XWorkMethodAccessor.DENY_METHOD_EXECUTION, Boolean.FALSE);



                invocationContext.put(XWorkConverter.REPORT_CONVERSION_ERRORS, Boolean.FALSE);



            }



        }



    }



    protected boolean acceptableName(String name) {



        if (name.indexOf(\'=\') != -1 || name.indexOf(\',\') != -1 || name.indexOf(\'#\') != -1) {



            return false;



        } else {



            return true;



        }



    }



}





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