添加数据库事务

//数据库事务 @Transactional(rollbackFor = Exception.class)
具体实例
`@Transactional(rollbackFor = Exception.class)
@Override
public String create(CreateOrderReq createOrderReq){
//拿到用户ID
Integer userId = UserFilter.currentUser.getId();
//从购物车查找已勾选的商品
List cartVOList = cartService.list(userId);
ArrayList cartVOListTemp = new ArrayList<>();
for (int i = 0; i < cartVOList.size(); i++) {
CartVO cartVO = cartVOList.get(i);
if (cartVO.getSelected().equals(Constant.Cart.CHECKED)){
cartVOListTemp.add(cartVO);
}
}
cartVOList = cartVOListTemp;
//如果购物车已勾选的为空，就报错
if(CollectionUtils.isEmpty(cartVOList)){
throw new ImoocMallException(ImoocMallExceptionEnum.CART_EMPTY);
}
//判断商品是否存在，上下架状态，库存
validSaleStatusAndStock(cartVOList);

//把购物车对象转化为订单item对象
List orderItemsList = cartVOListToOrderItemList(cartVOList);
//扣库存
for (int i = 0; i < orderItemsList.size(); i++) {
OrderItem orderItem = orderItemsList.get(i);
Product product = productMapper.selectByPrimaryKey(orderItem.getProductId());
int stock = product.getStock() - orderItem.getQuantity();
if (stock<0){
throw new ImoocMallException(ImoocMallExceptionEnum.NOT_ENOUGH);
}
product.setStock(stock);
productMapper.updateByPrimaryKeySelective(product);
}

//把购物车中的已勾选的商品删除
cleanCart(cartVOList);
//生成订单
Order order = new Order();
//生成订单号，有独立的规则
String orderNo = OrderCodeFactory.getOrderCode(Long.valueOf(userId));
order.setOrderNo(orderNo);
order.setUserId(userId);
order.setTotalPrice(totalPrice(orderItemsList));
order.setReceiverName(createOrderReq.getReceiverName());
order.setReceiverMobile(createOrderReq.getReceiverMobile());
order.setReceiverAddress(createOrderReq.getReceiverAddress());
order.setOrderStatus(Constant.OrderStatusEnum.NOT_PAID.getCode());
order.setPostage(0);
order.setPaymentType(1);
//插入到order表
orderMapper.insertSelective(order);

//循环保存每个商品的order_item表
for (int i = 0; i < orderItemsList.size(); i++) {
OrderItem orderItem = orderItemsList.get(i);
orderItem.setOrderNo(order.getOrderNo());
orderItemMapper.insertSelective(orderItem);

}

//把结果返回

return orderNo;
}`