private Spreadsheet convertDownloadItemToSpreadsheet(DownloadItem di) {
   Spreadsheet sp = new Spreadsheet();
   sp.setTitle(di.getTitle());
   sp.setId(di.getAddress());
   sp.setUpdateDate(new Date());
   return sp;
 }
 private DownloadItem convertSpreadsheetToDownloadItem(Spreadsheet spreadsheet) {
   DownloadItem di = new DownloadItem();
   di.setTitle(spreadsheet.getTitle());
   di.setType(DownloadItem.ItemType.Spreadsheet);
   di.setAddress(spreadsheet.getId());
   return di;
 }