GWT下载

        if( RootPanel.get("downloadiframe") != null ) {  
            Widget widgetFrame = (Widget)RootPanel.get("downloadiframe");  
            widgetFrame.removeFromParent();  
        }   
        Frame frame = new Frame( GWT.getModuleBaseURL() + "filedownload" + "?id=downloadiframe"+  
                "&filename=" + filename );  
        frame.setVisible( false );  
        frame.setSize( "0px", "0px" );  
        RootPanel.get().add( frame ); 

   下载的Action在web.xml里配置就ＯＫ