// 1. 自定義冪等注解
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Idempotent {
    long timeout() default 10; // 過期時間，單位分鐘
}
 
// 2. AOP 實現(xiàn)
@Aspect
@Component
public class IdempotentAspect {
    @Autowired
    private StringRedisTemplate redisTemplate;
 
    @Around("@annotation(idempotent)")
    public Object around(ProceedingJoinPoint joinPoint, Idempotent idempotent) throws Throwable {
        HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.currentRequestAttributes()).getRequest();
        String token = request.getHeader("Idempotent-Token");
        // ... 校驗 Token 是否為空...
        String key = "idempotent:token:" + token;
        // 原子性驗證并刪除 Token
        Boolean isDeleted = redisTemplate.delete(key);
        if (Boolean.FALSE.equals(isDeleted)) {
            throw new BusinessException("請求已處理，請勿重復提交");
        }
        return joinPoint.proceed();
    }
}
 
// 3. 在控制器方法上使用注解
@PostMapping("/order")
@Idempotent(timeout = 10)
public Result createOrder(@RequestBody OrderRequest request) {
    // 業(yè)務邏輯
}

@Service
public class PaymentService {
    @Autowired
    private PaymentRepository paymentRepository;
 
    @Transactional
    public PaymentResponse processPayment(PaymentRequest request) {
        try {
            Payment payment = new Payment();
            payment.setOrderNo(request.getOrderNo());
            payment.setTransactionId(request.getTransactionId()); // 此字段有唯一索引
            payment.setAmount(request.getAmount());
            paymentRepository.save(payment);
            // ...其他支付邏輯...
            return new PaymentResponse(true, "支付成功");
        } catch (DataIntegrityViolationException e) {
            // 捕獲唯一約束違反異常
            Payment existingPayment = paymentRepository.findByTransactionId(request.getTransactionId());
            return new PaymentResponse(true, "支付已處理", existingPayment.getId());
        }
    }
}

// 實體類
@Data
public class InventoryItemDO {
    private Long id;
    private Integer sellableQuantity;
    @Version // 樂觀鎖版本號字段注解
    private Integer version;
}
 
// Mapper 接口中使用
public interface InventoryItemMapper extends BaseMapper<InventoryItemDO> {
    // MyBatis-Plus 會自動在更新時帶上版本條件
}
 
// Service 中調(diào)用 updateById 方法時，MyBatis-Plus 會自動處理版本號

@Service
public class SeckillService {
    @Autowired
    private RedissonClient redissonClient;
    @Autowired
    private OrderRepository orderRepository;
 
    public SeckillResponse seckill(SeckillRequest request) {
        String lockKey = "lock:seckill:" + request.getGoodsId();
        RLock lock = redissonClient.getLock(lockKey);
        try {
            if (lock.tryLock(3, 10, TimeUnit.SECONDS)) { // 嘗試獲取鎖，等待3秒，鎖持有10秒
                // 二次校驗：查詢是否已下單，防止重復處理
                if (orderRepository.existsByUserIdAndGoodsId(request.getUserId(), request.getGoodsId())) {
                    return SeckillResponse.alreadyOrdered();
                }
                // 執(zhí)行業(yè)務邏輯...
                return SeckillResponse.success();
            } else {
                throw new BusinessException("系統(tǒng)繁忙，請稍后再試");
            }
        } finally {
            if (lock.isHeldByCurrentThread()) {
                lock.unlock();
            }
        }
    }
}

@PostMapping("/transfer")
public Result transfer(@RequestBody TransferRequest request) {
    String idempotentKey = generateIdempotentKey(request); // 根據(jù)請求參數(shù)生成摘要
    String redisKey = "idempotent:digest:" + idempotentKey;
    // 原子性地設(shè)置鍵值，僅當鍵不存在時
    Boolean isFirstRequest = redisTemplate.opsForValue().setIfAbsent(redisKey, "processing", 24, TimeUnit.HOURS);
    if (Boolean.FALSE.equals(isFirstRequest)) {
        // 重復請求，可根據(jù)業(yè)務查詢之前的結(jié)果或直接返回錯誤
        return Result.fail("請勿重復提交");
    }
    try {
        // 執(zhí)行業(yè)務邏輯...
        return Result.success();
    } finally {
        // 可選：業(yè)務成功完成后，可以更新Redis中的狀態(tài)；若失敗，可刪除鍵允許重試
        // redisTemplate.delete(redisKey);
    }
}