code: protected void validateUrl(String field, String errorKey, String errorMessage) {
  		String value = controller.getPara(field);
  		if (StrKit.isBlank(value)) {
  			addError(errorKey, errorMessage);
  			return ;
  		}
  		try {
  			value = value.trim();
  			if (value.startsWith("https://")) {
  				value = "http://" + value.substring(8); // URL doesn't understand the https protocol, hack it
  			}
  			new URL(value);
  		} catch (MalformedURLException e) {
  			addError(errorKey, errorMessage);
  		}
  	}
docs: Validate URL.