arcgis api for flex 加载WMS带时间戳的气象服务

package dmPlug
{
?import com.esri.ags.Map;
?import com.esri.ags.SpatialReference;
?import com.esri.ags.geometry.Extent;
?import com.esri.ags.layers.ArcGISDynamicMapServiceLayer;
?import com.esri.ags.layers.DynamicMapServiceLayer;
?
?import flash.display.Loader;
?import flash.net.URLRequest;
?import flash.net.URLVariables;
?
?import mx.controls.Alert;
?
?public class WMSMapServiceLayer extends DynamicMapServiceLayer
?{
??internal const service:String="WMS";
??internal const request:String="GetMap"
??internal const scalar:Number=1;
??public var url:String;
??public var format:String="image/png";
??public var serviceName:String;
??public var urlWms:String;
??public var wmstVersion:String;
??public var styles:String;
??public var srs:String="EPSG:4326";
??public var transparentBG:String;
??private var _timeStamp:String;
??private var _layers:String;
??public function WMSMapServiceLayer()
??{
???super();
???this.setLoaded(true);
???this.url=url;
??}
??public function set timeStamp(value:String):void
??{
???_timeStamp=value;
??}
??public function set layers(value:String):void
??{
??? _layers=value;
??}
??override protected function loadMapImage(loader:Loader) : void
??{
???var mapExtent:Extent = map.extent;

???if (map.spatialReference)
???
???{
????mapExtent.spatialReference = map.spatialReference;
???}
???
???var spatialReference:SpatialReference = mapExtent.spatialReference;
???var pxHeight:Number =map.height;
???var pxWidth:Number =map.width;
???var _url:String=this.url;
???_url +"SERVICE="+service;
???_url += "&VERSION=1.1.1";
???_url += "&REQUEST="+request;
???_url += "&STYLES=";
???_url += "&layers="+_layers;?
???_url +="&timeStamp="+_timeStamp;
???_url += "&SRS="+srs;
???_url += "&FORMAT=image/png";
???_url += "&WIDTH="+pxWidth;
???_url += "&HEIGHT="+pxHeight;
???_url += "&BBOX="+this.map.extent.xmin+","+this.map.extent.ymin+","+this.map.extent.xmax+","+this.map.extent.ymax;?
???_url += "&transparent=true"
???_url += "&token=";
???_url += "&st=12434"
???var wmsReq:URLRequest = new URLRequest(_url);
???loader.load(wmsReq);
???return;
???
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??}
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?? ?} }