WebWork2源码分析续一

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;

        }

    }

}