// todo: format validation for e-mail, zip, credit card, date
public ActionErrors validate(ActionMapping mapping, HttpServletRequest request) {
Order order = getOrder();
ActionErrors errors = new ActionErrors();
Account account = order.getAccount();
addErrorIfStringEmpty(errors, "creditCart", "order.error.creditCard.required", order.getCreditCard());
addErrorIfStringEmpty(errors, "expirationDate", "order.error.expirationDate.required", order.getExprDate());
addErrorIfStringEmpty(errors, "cardType", "order.error.cardType.required", order.getCardType());