SpringBoot项目中实现接口幂等的代码详解

// 1. 自定义幂等注解
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Idempotent {
    long timeout() default 10; // 过期时间，单位分钟
}

// 2. AOP 实现
@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");
        // ... 校验 Token 是否为空...
        String key = "idempotent:token:" + token;
        // 原子性验证并删除 Token
        Boolean isDeleted = redisTemplate.delete(key);
        if (Boolean.FALSE.equals(isDeleted)) {
            throw new BusinessException("请求已处理，请勿重复提交");
        }
        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) {
    // 业务逻辑
}

@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);
            // ...其他支付逻辑...
            return new PaymentResponse(true, "支付成功");
        } catch (DataIntegrityViolationException e) {
            // 捕获唯一约束违反异常
            Payment existingPayment = paymentRepository.findByTransactionId(request.getTransactionId());
            return new PaymentResponse(true, "支付已处理", existingPayment.getId());
        }
    }
}

// 实体类
@Data
public class InventoryItemDO {
    private Long id;
    private Integer sellableQuantity;
    @Version // 乐观锁版本号字段注解
    private Integer version;
}

// Mapper 接口中使用
public interface InventoryItemMapper extends BaseMapper<InventoryItemDO> {
    // MyBatis-Plus 会自动在更新时带上版本条件
}

// Service 中调用 updateById 方法时，MyBatis-Plus 会自动处理版本号

@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)) { // 尝试获取锁，等待3秒，锁持有10秒
                // 二次校验：查询是否已下单，防止重复处理
                if (orderRepository.existsByUserIdAndGoodsId(request.getUserId(), request.getGoodsId())) {
                    return SeckillResponse.alreadyOrdered();
                }
                // 执行业务逻辑...
                return SeckillResponse.success();
            } else {
                throw new BusinessException("系统繁忙，请稍后再试");
            }
        } finally {
            if (lock.isHeldByCurrentThread()) {
                lock.unlock();
            }
        }
    }
}

@PostMapping("/transfer")
public Result transfer(@RequestBody TransferRequest request) {
    String idempotentKey = generateIdempotentKey(request); // 根据请求参数生成摘要
    String redisKey = "idempotent:digest:" + idempotentKey;
    // 原子性地设置键值，仅当键不存在时
    Boolean isFirstRequest = redisTemplate.opsForValue().setIfAbsent(redisKey, "processing", 24, TimeUnit.HOURS);
    if (Boolean.FALSE.equals(isFirstRequest)) {
        // 重复请求，可根据业务查询之前的结果或直接返回错误
        return Result.fail("请勿重复提交");
    }
    try {
        // 执行业务逻辑...
        return Result.success();
    } finally {
        // 可选：业务成功完成后，可以更新Redis中的状态；若失败，可删除键允许重试
        // redisTemplate.delete(redisKey);
    }
}