code: public void required(final String tagName, final String actionName, final String attributeName, final Object attribute) throws PageException {
  	if (attribute == null) {
  	    final Excepton util = CFMLEngineFactory.getInstance().getExceptionUtil();
  	    throw util.createApplicationException("Attribute [" + attributeName + "] for tag [" + tagName + "] is required if attribute action has the value [" + actionName + "]");
  	}
      }
docs: check if value is not empty
  
  @param tagName
  @param actionName
  @param attributeName
  @param attribute
  @throws PageException