Redis实现限量优惠券的秒杀

核心：避免超卖问题，保证一人一单 

业务逻辑

 

代码步骤分析

全部代码

@Service
public class VoucherOrderServiceImpl extends ServiceImpl<VoucherOrderMapper, VoucherOrder> implements IVoucherOrderService {@Resourceprivate ISeckillVoucherService seckillVoucherService;@Resourceprivate RedisIdWorker redisIdWorker;@Resourceprivate StringRedisTemplate stringRedisTemplate;@Resourceprivate RedissonClient redissonClient;@Overridepublic Result seckillVoucher(Long voucherId) {//1 查询优惠券信息SeckillVoucher seckillVoucher = seckillVoucherService.getById(voucherId);//2 判断秒杀是否开始LocalDateTime now = LocalDateTime.now(); //现在时间LocalDateTime beginTime = seckillVoucher.getBeginTime(); //开始时间LocalDateTime endTime = seckillVoucher.getEndTime(); //结束时间if (now.isBefore(beginTime)) {return Result.fail("秒杀还未开始");}//3 判断秒杀是否结束if (now.isAfter(endTime)) {return Result.fail("秒杀已结束");}//4 判断库存是否充足int stock = (int) seckillVoucher.getStock();if (stock == 0 && stock <= 0) {return Result.fail("库存不足");}//确保一人一单 用户ID和代金券ID联合查询Long userId = UserHolder.getUser().getId();//先获取锁 再提交事务//synchronized (userId.toString().intern()) {//创建锁对象//SimpleRedisLock simpleRedisLock = new SimpleRedisLock("order:" + userId, stringRedisTemplate);RLock lock = redissonClient.getLock("lock:order:" + userId);//获取锁boolean isLock = lock.tryLock();//判断是否获取锁成功if (!isLock){//获取锁失败 返回错误或失败return Result.fail("不允许重复下单");}try {//获取事务的代理对象IVoucherOrderService proxy = (IVoucherOrderService) AopContext.currentProxy();return proxy.creatVoucherOrder(voucherId);} finally {//释放锁lock.unlock();}//}//事务提交之后在释放锁}/*** 这里对于加锁做出一些解释：如果锁加在整个方法上，那么就会导*  致锁的粒度过大，导致每个进程进来都会锁住，所以要控制锁的粒度*/@Transactionalpublic Result creatVoucherOrder(Long voucherId) {Long userId = UserHolder.getUser().getId();Integer count = query().eq("user_id", userId).eq("voucher_id", voucherId).count();if (count > 0) {return Result.fail("用户已经购买过了");}//5 扣减库存-boolean success = seckillVoucherService.update().setSql("stock = stock -1 ")  //乐观锁.eq("voucher_id", voucherId).gt("stock", 0) //判断库存是否大于0: where id = ? and stock > 0.update();if (!success) {return Result.fail("库存不足");}//6 创建订单//6.1 订单IDVoucherOrder voucherOrder = new VoucherOrder();long orderid = RedisIdWorker.nextId("order");voucherOrder.setVoucherId(orderid);//6.2 用户IDvoucherOrder.setUserId(userId);//6.3 代金券IDvoucherOrder.setVoucherId(voucherId);save(voucherOrder);//7 返回订单idreturn Result.ok(orderid);}}