Day4-微服务-Seata默认事务

以上篇文章为基础，本章讲解AT事务的使用。以火车抢票系统为例

1.GlobalTransactional注解的使用

GlobalTransactional要放在事务的发起方的Service层上的public方法上

在service的实现类上，加入注解，那么逻辑就是，用户在确认订单后，系统会在会员模块中给会员加入一条购票记录，如果中间确认订单出现问题，seata就是触发回滚将数据全部回滚。当前确认订单这个service就是事务的发起方，在business模块里。member模块里的只是参与方。

Seata 在发起方的 @GlobalTransactional 方法开始时创建全局事务 ID（XID），通过 Feign 请求头自动传给 member，member 的 Seata 数据源代理根据 XID 把自己加入全局事务。参与者不需要注解，Seata 自动识别。

@Service
public class AfterConfirmOrderServiceImpl implements AfterConfirmOrderService {

    private static final Logger LOG = LoggerFactory.getLogger(AfterConfirmOrderServiceImpl.class);

    @Resource
    private DailyTrainSeatMapper dailyTrainSeatMapper;

    @Resource
    private DailyTrainTicketMapperCust dailyTrainTicketMapperCust;

    @Resource
    private MemberFeign memberFeign;

    @Resource
    private ConfirmOrderMapper confirmOrderMapper;

    /**
     * 选中座位后事务处理：
     * 座位表修改售卖情况sell；
     * 余票详情表修改余票；
     * 为会员增加购票记录
     * 更新确认订单为成功
     */
    
    @GlobalTransactional
    @Override
    public void afterDoConfirm(DailyTrainTicket dailyTrainTicket, List<DailyTrainSeat> finalSeatList, List<ConfirmOrderTicketReq> tickets, ConfirmOrder confirmOrder) {

        LOG.info("seata全局事务ID: {}", RootContext.getXID());

        for (int j = 0; j < finalSeatList.size(); j++) {
            DailyTrainSeat dailyTrainSeat = finalSeatList.get(j);
            DailyTrainSeat seatForUpdate = new DailyTrainSeat();
            seatForUpdate.setId(dailyTrainSeat.getId());
            seatForUpdate.setSell(dailyTrainSeat.getSell());
            seatForUpdate.setUpdateTime(new Date());
            dailyTrainSeatMapper.updateByPrimaryKeySelective(seatForUpdate);
            Integer startIndex = dailyTrainTicket.getStartIndex();
            Integer endIndex = dailyTrainTicket.getEndIndex();
            char[] chars = seatForUpdate.getSell().toCharArray();
            Integer maxStartIndex = endIndex - 1;
            Integer minEndIndex = startIndex + 1;
            int minStartIndex = 0;
            for (int i = startIndex - 1; i >= 0; i--) {
                char aChar = chars[i];
                if (aChar == '1') {
                    minStartIndex = i + 1;
                    break;
                }
            }
            LOG.info("影响出发站区间：" + minStartIndex + "-" + maxStartIndex);

            Integer maxEndIndex = seatForUpdate.getSell().length() + 1;
            for (int i = endIndex; i < seatForUpdate.getSell().length(); i++) {
                char aChar = chars[i];
                if (aChar == '1') {
                    maxEndIndex = i + 1;
                    break;
                }
            }
            LOG.info("影响到达站区间：" + minEndIndex + "-" + maxEndIndex);

            dailyTrainTicketMapperCust.updateCountBySell(
                    dailyTrainSeat.getDate(),
                    dailyTrainSeat.getTrainCode(),
                    dailyTrainSeat.getSeatType(),
                    minStartIndex,
                    maxStartIndex,
                    minEndIndex,
                    maxEndIndex);

            // 调用会员服务接口，为会员增加一张车票
            MemberTicketReq memberTicketReq = new MemberTicketReq();
            memberTicketReq.setMemberId(confirmOrder.getMemberId());
            memberTicketReq.setPassengerId(tickets.get(j).getPassengerId());
            memberTicketReq.setPassengerName(tickets.get(j).getPassengerName());
            memberTicketReq.setTrainDate(dailyTrainTicket.getDate());
            memberTicketReq.setTrainCode(dailyTrainTicket.getTrainCode());
            memberTicketReq.setCarriageIndex(dailyTrainSeat.getCarriageIndex());
            memberTicketReq.setSeatRow(dailyTrainSeat.getRow());
            memberTicketReq.setSeatCol(dailyTrainSeat.getCol());
            memberTicketReq.setStartStation(dailyTrainTicket.getStart());
            memberTicketReq.setStartTime(dailyTrainTicket.getStartTime());
            memberTicketReq.setEndStation(dailyTrainTicket.getEnd());
            memberTicketReq.setEndTime(dailyTrainTicket.getEndTime());
            memberTicketReq.setSeatType(dailyTrainSeat.getSeatType());
            Result<Object> commonResp = memberFeign.save(memberTicketReq);
            LOG.info("调用member接口，返回：{}", commonResp);

            // 更新订单状态为成功
            ConfirmOrder confirmOrderForUpdate = new ConfirmOrder();
            confirmOrderForUpdate.setId(confirmOrder.getId());
            confirmOrderForUpdate.setUpdateTime(new Date());
            confirmOrderForUpdate.setStatus(ConfirmOrderStatusEnum.SUCCESS.getCode());
            confirmOrderMapper.updateByPrimaryKeySelective(confirmOrderForUpdate);
        }
    }
}

在需要参与事务的模块的数据库中加入undo_log表，这是AT事务开启的关键！