@Override
    public boolean isValid(Object fieldValue) {
        if (fieldValue == null) {
            return true;
        }
        return fieldValue.toString().matches("^[a-z]([a-z0-9]*[-_]?[a-z0-9]+)*@([a-z0-9]*[-_]?[a-z0-9]+)+[\\.][a-z]{2,3}([\\.][a-z]{2})?$");
    }