民宿预订系统优惠券营销模块设计要点

@Service
public class CouponReceiveService {
    @Autowired
    private StringRedisTemplate redisTemplate;
    @Autowired
    private CouponBatchMapper batchMapper;
    @Autowired
    private UserCouponMapper userCouponMapper;
    // 分布式锁前缀
    private static final String LOCK_PREFIX = "coupon:lock:";
    // 库存缓存key
    private static final String STOCK_PREFIX = "coupon:stock:";

    @Transactional(rollbackFor = Exception.class)
    public ResultDTO receiveCoupon(Long userId, Long batchId) {
        String lockKey = LOCK_PREFIX + userId + ":" + batchId;
        // 1. 获取Redis分布式锁
        Boolean lock = redisTemplate.opsForValue().setIfAbsent(lockKey, "1", 30, TimeUnit.SECONDS);
        if (!lock) {
            return ResultDTO.fail("请勿重复领取优惠券");
        }
        try {
            // 2. 校验缓存库存
            String stockStr = redisTemplate.opsForValue().get(STOCK_PREFIX + batchId);
            if (StringUtils.isEmpty(stockStr) || Integer.parseInt(stockStr) <= 0) {
                return ResultDTO.fail("优惠券已领完");
            }
            // 3. 扣减缓存库存
            Long decrement = redisTemplate.opsForValue().decrement(STOCK_PREFIX + batchId);
            if (decrement < 0) {
                redisTemplate.opsForValue().increment(STOCK_PREFIX + batchId);
                return ResultDTO.fail("优惠券已领完");
            }
            // 4. 写入用户优惠券记录，唯一索引防止重复入库
            UserCoupon userCoupon = new UserCoupon();
            userCoupon.setUserId(userId);
            userCoupon.setBatchId(batchId);
            userCoupon.setStatus(0);
            userCouponMapper.insert(userCoupon);
            return ResultDTO.success("领券成功");
        } finally {
            // 释放分布式锁
            redisTemplate.delete(lockKey);
        }
    }
}

public interface CouponRuleStrategy {
    /**
     * 校验优惠券是否可用
     * @param userCoupon 用户券
     * @param orderDTO 预订订单信息
     * @return 校验结果
     */
    CheckResult check(UserCoupon userCoupon, HomestayOrderDTO orderDTO);
}

// 连住优惠券实现类
@Component
public class NightCouponStrategy implements CouponRuleStrategy {
    @Override
    public CheckResult check(UserCoupon userCoupon, HomestayOrderDTO orderDTO) {
        CouponBatch batch = batchMapper.selectById(userCoupon.getBatchId());
        // 校验入住晚数
        if (orderDTO.getNightCount() < batch.getMinNights()) {
            return CheckResult.fail("未达到最低入住晚数要求");
        }
        // 校验民宿匹配
        if (!batch.getHomestayIdList().contains(orderDTO.getHomestayId())) {
            return CheckResult.fail("该优惠券不适用于当前民宿");
        }
        return CheckResult.success();
    }
}