flex文件下载

1flex端
<mx:Button label="下 载" click="download()"/>
//下载
  public function download():void{
   var str:String=this.uploadfiles.selectedIndex.toString();
   if(str=="-1"){
    Alert.show("请选中要下载的文件");
   }else{
    downloadfiles();
   }
  }
  public function downloadfiles():void{
   var loadid:String=this.uploadfiles.selectedItem.loadid;
   if(loadid==null || loadid==""){
      Alert.show("对不起，该文件还未上传");
      }    
      var urlAddress:String=model.root+"/uploadFiles.do?method=download&loadid="+loadid;   
      //URLRequest可以捕获单个HTTP的所有信息
      var url:URLRequest=new URLRequest(urlAddress);
         var loadname:String=this.uploadfiles.selectedItem.loadname;
         //download()方法提示用户提供文件的保存位置并开始从远程 URL 进行下载。
         filedown.download(url,loadname);
  }
  protected override  function createChildren():void{
   super.createChildren();
   filedown.addEventListener(Event.COMPLETE,onDownCompleted);
  }
  public  function  onDownCompleted(evt:Event):void{
     this.resultlabel.visible=true;
        var fileref:FileReference = evt.currentTarget as FileReference;
        resultlabel.text = "文件名:" + uploadfiles.selectedItem.loadname+ "下载完毕！";     
  }
java后台(action)
 /**
  * 文件下载
  *
  * @param mapping
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