仿12306项目选座购票业务逻辑

12306项目选座购票业务逻辑

项目分享

近期在跟视频做SpringBoot微服务项目12306，可点击查看项目。可私信分享项目资料。

此篇记录12306中的重点业务逻辑流程，选座购票业务逻辑。

选座逻辑

分成选座和不选座

• 不选座，以购买一等座为例：遍历一等座车厢，每个车厢从1号座位开始找，未被购买的，就选中它
• 选座，以购买两张一等座AB为例：遍历一等座车厢，每个车厢从1号座位开始找A列座位，未被购买的，就预选中它；再挑它旁边的B，如果也未被购买，则最终选中这两个座位，如果B已被购买，则回到第一步，继续找未被购买的A座。

从第二个座位开始，需要计算和第一个座位的偏移值，可以减少循环，提高选座效率

选择C1，D2，偏移值为[0, 5]

选择B1，D2，偏移值为[0, 7]
选择A1，B1，C1，则偏移值为[0，1，2]
由此可见，偏移值都是针对第一个选座位置的偏移量，并且第一个永远是0

购票逻辑

计算某座位在区间内是否可卖
例：

有站点ABCDEF，则设置sell=10001，1表示座位在区间已卖出，0表示未卖出
本次购买区间站1~4，则区间已售000，全部是0，表示这个区间可买；只要有1，就表示区间内已售过票

选中座位后，应完成：

选中后，要计算购票后的sell，比如原来是10001，本次购买区间站1~4
方案：构造本次购票造成的售卖信息01110，和原sell10001按位或，最终得到11111

以上转化为字符串的截取和位运算

更新余票逻辑

重点逻辑

购买一张票将会影响的库存：本次选座之前没卖过票的，和本次购买的区间有交集的区间

假设10个站，本次买4~7站
原售:001000001
购买:000011100
新售:001011101
影响:XXX11111X
Integer startIndex = 4;
Integer endIndex = 7;
Integer minStartIndex = startIndex - (往前碰到的最后一个0);
Integer maxStartIndex = endIndex - 1;
Integer minEndIndex = startIndex + 1;
Integer maxEndIndex = endIndex + (往后碰到的最后一个0);
因此要更新的余票为：
minStartIndex <= start_index <= maxStartIndex &&
minEndIndex <= end_index <= maxEndIndex

用户选座功能

前端传递数据：

    {passengerId: 123,passengerType: "1",passengerName: "张三",passengerIdCard: "12323132132",seatTypeCode: "2",seat: "C1"}

用户分为选座和不选座，不选座则seat字段为空，由后端自动分配座位；选座则seat字段为所选座位信息，一等座，则seatTypeCode为1，二等座为2，自动提供两排备选座位。

C1表示选择第1排的C号座位。

服务器售票功能

0. 业务数据校验

主要目的是防止恶意请求，直接绕过前端访问后端接口

车次是否存在，余票是否存在，车次是否在有效期内，tickets条数>0，同乘客同车次是否已买过

1. 保存确认订单表，状态初始化

2. 查出余票记录，需要得到真是的库存

DailyTrainTicket dailyTrainTicket = dailyTrainTicketService.selectByUnique(date, trainCode, start, end);

3. 扣减余票数量，并判断余票是否足够

    private static void reduceTickets(ConfirmOrderDoReq req, DailyTrainTicket dailyTrainTicket) {for (ConfirmOrderTicketReq ticketReq : req.getTickets()) {String seatTypeCode = ticketReq.getSeatTypeCode();SeatTypeEnum seatTypeEnum = EnumUtil.getBy(SeatTypeEnum::getCode, seatTypeCode);switch (seatTypeEnum) {case YDZ -> {int countLeft = dailyTrainTicket.getYdz() - 1;if (countLeft < 0) {throw new BusinessException(BusinessExceptionEnum.CONFIRM_ORDER_TICKET_COUNT_ERROR);}dailyTrainTicket.setYdz(countLeft);}case EDZ -> {int countLeft = dailyTrainTicket.getEdz() - 1;if (countLeft < 0) {throw new BusinessException(BusinessExceptionEnum.CONFIRM_ORDER_TICKET_COUNT_ERROR);}dailyTrainTicket.setEdz(countLeft);}case RW -> {int countLeft = dailyTrainTicket.getRw() - 1;if (countLeft < 0) {throw new BusinessException(BusinessExceptionEnum.CONFIRM_ORDER_TICKET_COUNT_ERROR);}dailyTrainTicket.setRw(countLeft);}case YW -> {int countLeft = dailyTrainTicket.getYw() - 1;if (countLeft < 0) {throw new BusinessException(BusinessExceptionEnum.CONFIRM_ORDER_TICKET_COUNT_ERROR);}dailyTrainTicket.setYw(countLeft);}}}}

4. 选座开始

计算相对第一个座位的偏移值

eg:
一等座选择C1，D2，则偏移值为[0，5]
二等座选择A1，B1，C1，则偏移值为[0，1，2]

根据订单中订票座位类型，构造出和前端两排选座一样的列表，用于作参考的座位列表，例如：

referSeatList = {A1, C1, D1, F1, A2, C2, D2, F2}
referSeatList = {A1, B1, C1, D1, F1, A2, B2, C2, D2, F2}

接着再根据订单中的座位，计算全部座位的绝对偏移值，即在referSeatList 数组中的下标位置，最后每一个座位减去首个座位的下标位置，可以得到偏移值数组。

// 计算相对第一个座位的偏移值// 比如选择的是C1,D2，则偏移值是：[0,5]// 比如选择的是A1,B1,C1，则偏移值是：[0,1,2]ConfirmOrderTicketReq ticketReq0 = tickets.get(0);if (StrUtil.isNotBlank(ticketReq0.getSeat())) {LOG.info("本次购票有选座");// 查出本次选座的座位类型都有哪些列，用于计算所选座位与第一个座位的偏离值List<SeatColEnum> colEnumList = SeatColEnum.getColsByType(ticketReq0.getSeatTypeCode());LOG.info("本次选座的座位类型包含的列：{}", colEnumList);// 组成和前端两排选座一样的列表，用于作参照的座位列表，例：referSeatList = {A1, C1, D1, F1, A2, C2, D2, F2}List<String> referSeatList = new ArrayList<>();for (int i = 1; i <= 2; i++) {for (SeatColEnum seatColEnum : colEnumList) {referSeatList.add(seatColEnum.getCode() + i);}}LOG.info("用于作参照的两排座位：{}", referSeatList);List<Integer> offsetList = new ArrayList<>();// 绝对偏移值，即：在参照座位列表中的位置List<Integer> aboluteOffsetList = new ArrayList<>();for (ConfirmOrderTicketReq ticketReq : tickets) {int index = referSeatList.indexOf(ticketReq.getSeat());aboluteOffsetList.add(index);}LOG.info("计算得到所有座位的绝对偏移值：{}", aboluteOffsetList);for (Integer index : aboluteOffsetList) {int offset = index - aboluteOffsetList.get(0);offsetList.add(offset);}LOG.info("计算得到所有座位的相对第一个座位的偏移值：{}", offsetList);getSeat(finalSeatList,date,trainCode,ticketReq0.getSeatTypeCode(),ticketReq0.getSeat().split("")[0], // 从A1得到AoffsetList,dailyTrainTicket.getStartIndex(),dailyTrainTicket.getEndIndex());}

打印结果：

4.1 一个车厢一个车厢获取座位数据

根据对应的车座类型，循环查找车次的对应车厢，如一等组车厢

再在每个车厢中，寻找符合偏移值条件的车座

4.2 挑选符合条件的座位，如果这个车厢不满足，则进入下一个车厢（多个选座应在一个车厢）

对于每一个未售卖且列号等于初始座位的座位，选中其。

接着判断各偏移量座位，只有全部偏移量座位都可选中，才能选中这些座位，否则要退出重选。

同时注意偏移量座位的座位号不能大于车厢座位数量，因为要保证在同一车厢。

    /*** 挑座位，如果有选座，则一次性挑完，如果无选座，则一个一个挑* @param date* @param trainCode* @param seatType* @param column* @param offsetList*/private void getSeat(List<DailyTrainSeat> finalSeatList, Date date, String trainCode, String seatType, String column, List<Integer> offsetList, Integer startIndex, Integer endIndex) {List<DailyTrainSeat> getSeatList = new ArrayList<>();List<DailyTrainCarriage> carriageList = dailyTrainCarriageService.selectBySeatType(date, trainCode, seatType);LOG.info("共查出{}个符合条件的车厢", carriageList.size());// 一个车箱一个车箱的获取座位数据for (DailyTrainCarriage dailyTrainCarriage : carriageList) {LOG.info("开始从车厢{}选座", dailyTrainCarriage.getIndex());getSeatList = new ArrayList<>();List<DailyTrainSeat> seatList = dailyTrainSeatService.selectByCarriage(date, trainCode, dailyTrainCarriage.getIndex());LOG.info("车厢{}的座位数：{}", dailyTrainCarriage.getIndex(), seatList.size());for (int i = 0; i < seatList.size(); i++) {DailyTrainSeat dailyTrainSeat = seatList.get(i);Integer seatIndex = dailyTrainSeat.getCarriageSeatIndex();String col = dailyTrainSeat.getCol();// 判断当前座位不能被选中过boolean alreadyChooseFlag = false;for (DailyTrainSeat finalSeat : finalSeatList){if (finalSeat.getId().equals(dailyTrainSeat.getId())) {alreadyChooseFlag = true;break;}}if (alreadyChooseFlag) {LOG.info("座位{}被选中过，不能重复选中，继续判断下一个座位", seatIndex);continue;}// 判断column，有值的话要比对列号if (StrUtil.isBlank(column)) {LOG.info("无选座");} else {if (!column.equals(col)) {LOG.info("座位{}列值不对，继续判断下一个座位，当前列值：{}，目标列值：{}", seatIndex, col, column);continue;}}boolean isChoose = calSell(dailyTrainSeat, startIndex, endIndex);if (isChoose) {LOG.info("选中座位");getSeatList.add(dailyTrainSeat);} else {continue;}// 根据offset选剩下的座位boolean isGetAllOffsetSeat = true;if (CollUtil.isNotEmpty(offsetList)) {LOG.info("有偏移值：{}，校验偏移的座位是否可选", offsetList);// 从索引1开始，索引0就是当前已选中的票for (int j = 1; j < offsetList.size(); j++) {Integer offset = offsetList.get(j);// 座位在库的索引是从1开始// int nextIndex = seatIndex + offset - 1;int nextIndex = i + offset;// 有选座时，一定是在同一个车箱if (nextIndex >= seatList.size()) {LOG.info("座位{}不可选，偏移后的索引超出了这个车箱的座位数", nextIndex);isGetAllOffsetSeat = false;break;}DailyTrainSeat nextDailyTrainSeat = seatList.get(nextIndex);boolean isChooseNext = calSell(nextDailyTrainSeat, startIndex, endIndex);if (isChooseNext) {LOG.info("座位{}被选中", nextDailyTrainSeat.getCarriageSeatIndex());getSeatList.add(nextDailyTrainSeat);} else {LOG.info("座位{}不可选", nextDailyTrainSeat.getCarriageSeatIndex());isGetAllOffsetSeat = false;break;}}}if (!isGetAllOffsetSeat) {getSeatList = new ArrayList<>();continue;}// 保存选好的座位finalSeatList.addAll(getSeatList);return;}}}

计算某座位在区间内是否可卖：

/*** 计算某座位在区间内是否可卖* 例：sell=10001，本次购买区间站1~4，则区间已售000* 全部是0，表示这个区间可买；只要有1，就表示区间内已售过票** 选中后，要计算购票后的sell，比如原来是10001，本次购买区间站1~4* 方案：构造本次购票造成的售卖信息01110，和原sell 10001按位与，最终得到11111*/private boolean calSell(DailyTrainSeat dailyTrainSeat, Integer startIndex, Integer endIndex) {// 00001, 00000String sell = dailyTrainSeat.getSell();//  000, 000String sellPart = sell.substring(startIndex, endIndex);if (Integer.parseInt(sellPart) > 0) {LOG.info("座位{}在本次车站区间{}~{}已售过票，不可选中该座位", dailyTrainSeat.getCarriageSeatIndex(), startIndex, endIndex);return false;} else {LOG.info("座位{}在本次车站区间{}~{}未售过票，可选中该座位", dailyTrainSeat.getCarriageSeatIndex(), startIndex, endIndex);//  111,   111String curSell = sellPart.replace('0', '1');// 0111,  0111curSell = StrUtil.fillBefore(curSell, '0', endIndex);// 01110, 01110curSell = StrUtil.fillAfter(curSell, '0', sell.length());// 当前区间售票信息curSell 01110与库里的已售信息sell 00001按位与，即可得到该座位卖出此票后的售票详情// 15(01111), 14(01110 = 01110|00000)int newSellInt = NumberUtil.binaryToInt(curSell) | NumberUtil.binaryToInt(sell);//  1111,  1110String newSell = NumberUtil.getBinaryStr(newSellInt);// 01111, 01110newSell = StrUtil.fillBefore(newSell, '0', sell.length());LOG.info("座位{}被选中，原售票信息：{}，车站区间：{}~{}，即：{}，最终售票信息：{}", dailyTrainSeat.getCarriageSeatIndex(), sell, startIndex, endIndex, curSell, newSell);dailyTrainSeat.setSell(newSell);return true;}}

5. 选中座位后事务处理

5.1 座位表修改售卖情况为sell

5.2 余票详情表修改余票

5.3 为会员增加购票记录

5.4 更新确认订单为成功

/*** 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*/// @Transactional// @GlobalTransactionalpublic void afterDoConfirm(DailyTrainTicket dailyTrainTicket, List<DailyTrainSeat> finalSeatList, List<ConfirmOrderTicketReq> tickets, ConfirmOrder confirmOrder) throws Exception {// LOG.info("se ata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());.setUpdateTime(new Date());dailyTrainSeatMapper.updateByPrimaryKeySelective(seatForUpdate);// 计算这个站卖出去后，影响了哪些站的余票库存// 参照2-3节 如何保证不超卖、不少卖，还要能承受极高的并发 10:30左右// 影响的库存：本次选座之前没卖过票的，和本次购买的区间有交集的区间// 假设10个站，本次买4~7站// 原售：001000001// 购买：000011100// 新售：001011101// 影响：XXX11111X// Integer startIndex = 4;// Integer endIndex = 7;// Integer minStartIndex = startIndex - 往前碰到的最后一个0;// Integer maxStartIndex = endIndex - 1;// Integer minEndIndex = startIndex + 1;// Integer maxEndIndex = endIndex + 往后碰到的最后一个0;Integer startIndex = dailyTrainTicket.getStartIndex();Integer endIndex = dailyTrainTicket.getEndIndex();char[] chars = seatForUpdate.getSell().toCharArray();Integer maxStartIndex = endIndex - 1;Integer minEndIndex = startIndex + 1;Integer 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();for (int i = endIndex; i < seatForUpdate.getSell().length(); i++) {char aChar = chars[i];if (aChar == '1') {maxEndIndex = i;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());CommonResp<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);}}

同时利用feign调用member模块的save接口，保存购票信息

@FeignClient(name = "member", url = "http://127.0.0.1:8001")
public interface MemberFeign {@GetMapping("/member/feign/ticket/save")CommonResp<Object> save(@RequestBody MemberTicketReq req);}

member模块中：

@RestController
@RequestMapping("/feign/ticket")
public class FeignTicketController {@Autowiredprivate TicketService ticketService;@PostMapping("/save")public CommonResp<Object> save(@Valid @RequestBody MemberTicketReq req) throws Exception {ticketService.save(req);return new CommonResp<>();}}