code: protected void validateInteger(int index, String errorKey, String errorMessage) {
  		String value = controller.getPara(index);
  		if (value != null && (value.startsWith("N") || value.startsWith("n"))) {
  			value = "-" + value.substring(1);
  		}
  		validateIntegerValue(value, errorKey, errorMessage);
  	}
docs: Validate integer for urlPara.