code: public static void streamFileExcelTo (@Nonnull final UnifiedResponse aUR)
    {
      // Do it in a read lock!
      s_aRWLock.readLock ().lock ();
      try
      {
        final File f = _getFileExcel ();
        // setContent(IReadableResource) is lazy
        aUR.setContent (new FileSystemResource (f));
      }
      finally
      {
        s_aRWLock.readLock ().unlock ();
      }
    }
docs: Stream the stored Excel file to the provided HTTP response
  
  @param aUR
  The response to stream to. May not be <code>null</code>.