code: private void required(String attributeName, String atttributValue) throws ApplicationException {
  	if (atttributValue == null)
  	    throw new ApplicationException("invalid attribute constelation for the tag ftp", "attribute [" + attributeName + "] is required, if action is [" + action + "]");
      }
docs: throw a error if the value is empty (null)
  
  @param attributeName
  @param atttributValue
  @throws ApplicationException