code: public static void sendCurrentWarning(Object source, String msg)
    {
      WarningSystem warning = getCurrent();
      
      if (warning != null)
        warning.sendWarning(source, msg);
      else {
        Thread.dumpStack();
        System.err.println(msg);
        log.warning(msg);
      }
    }
docs: Sends a warning to the current service.