问来自VO的HTTPService出现问题

EN

package ValueObjects
{
    import mx.rpc.events.ResultEvent;
    import mx.rpc.http.HTTPService;

    [Bindable]
    public class Indicator
    {
        protected var service:HTTPService;

        public function Indicator( id:int , name:String , group_id:int, alias:String)
        {
        }   

        public function getfields():void
        {
            this.service = new HTTPService();
            service.url = "Here is my url - i've tested it and its working"
            trace(service.url);
            service.addEventListener(ResultEvent.RESULT, createFields);
            service.send();
        }

        public function createFields(event:ResultEvent):void
        {
            trace("got here");
            service.removeEventListener(ResultEvent.RESULT, createFields);
        }

    }
}