When I create action extension, the command class can not response

Hi Vmware member or other:

I do not understand why my command class can not response my action behavior.

The following is my configuration and implementation.

plugin.xml

--------------------------------------------------------------------------------------------------------------------------->

      <extension id="com.todo.DatacenterAction">

        <extendedPoint>vise.actions.sets</extendedPoint>

        <object>

            <actions>

                <com.vmware.actionsfw.ActionSpec>

                    <uid>com.todo.actions.DatacenterAction1</uid>

                    <label>TEST</label>

                    <command className="com.todo.actions.DatacenterActionCommand"/>

                </com.vmware.actionsfw.ActionSpec>

            </actions>

        </object>

        <metadata>

            <objectType>Datacenter</objectType>

        </metadata>

    </extension>

------------------------------------------------------------------------------------------------------------------------>

package com.todo.actions {

import com.vmware.actionsfw.ActionContext;

import com.vmware.actionsfw.events.ActionInvocationEvent;

import com.vmware.core.model.IResourceReference;

import com.vmware.flexutil.events.MethodReturnEvent;

import flash.events.EventDispatcher;

import mx.controls.Alert;

import mx.logging.ILogger;

import mx.logging.Log;

/**

* Command class to handle the actions defined in plugin.xml.

* It uses a <code>RequestHandler</code> for each <code>ActionSpec</code>'s uid

*/

  public class DatacenterActionCommand extends EventDispatcher {

     //private var _proxy:ActionCommandProxy = new ActionCommandProxy();

     private static var _logger:ILogger = Log.getLogger('com.fujitsu.vsm.vx700.actions.DatacenterActionCommand');

     [RequestHandler("com.fujitsu.vsm.vx700.actions.DatacenterAction1")]

     public function onDatacenterAction1(event:ActionInvocationEvent):void {

         Alert.show("Hello world");

     }

  }

}

----------------------------------------------------------------------------->

So, when I click "TEST" action, the screen doesn't popup "Hello world" dialog. Why?

I will be very appreciated if someone could help me.

Thanks