the solution is this:
String percorso = "/28.txt
try {
Filedownload.save(percorso,null);
} catch (Exception e) {
Messagebox.show("Errore recupero risorsa "+percorso);
}
but the problem is probably in the upload you shuld use this path for the upload : String path = Executions.getCurrent().getDesktop().getWebApp().getRealPath("/")+"folder/";