对Java接口进行幂等性控制的三种方法

ALTER TABLE t_order ADD UNIQUE KEY uk_client_order_no (client_order_no);

public void createOrder(String clientOrderNo, OrderDTO dto) {
    try {
        Order order = new Order();
        order.setClientOrderNo(clientOrderNo);
        order.setAmount(dto.getAmount());
        order.setUserId(dto.getUserId());
        orderRepository.insert(order); // 会触发唯一索引约束
    } catch (DuplicateKeyException e) {
        log.warn("订单已存在，幂等处理: {}", clientOrderNo);
        // 查询已有订单并返回，保持幂等
        Order existing = orderRepository.findByClientOrderNo(clientOrderNo);
        return existing;
    }
}

public boolean tryAcquireRequest(String key, long expireSeconds) {
    // 原子设置键 + 过期时间，表示该请求已处理
    return Boolean.TRUE.equals(
        redisTemplate.opsForValue().setIfAbsent(key, "1", Duration.ofSeconds(expireSeconds))
    );
}

@PostMapping("/api/pay")
public ResponseEntity<?> doPay(@RequestBody PayRequest request) {
    String redisKey = "pay:" + request.getUserId() + ":" + request.getOrderId();

    if (!idempotentService.tryAcquireRequest(redisKey, 30)) {
        return ResponseEntity.status(HttpStatus.CONFLICT).body("重复请求，请稍后再试");
    }

    // 执行支付逻辑
    paymentService.pay(request.getOrderId());

    return ResponseEntity.ok("支付成功");
}

@GetMapping("/token")
public String generateToken() {
    String token = UUID.randomUUID().toString();
    redisTemplate.opsForValue().set("token:" + token, "1", Duration.ofMinutes(5));
    return token;
}

@PostMapping("/submit")
public ResponseEntity<?> submitForm(@RequestParam String token, @RequestBody FormDTO form) {
    String redisKey = "token:" + token;

    // Redis 的 delete 操作返回 1 表示成功删除（即 token 存在）
    Boolean success = redisTemplate.delete(redisKey);

    if (Boolean.FALSE.equals(success)) {
        return ResponseEntity.status(HttpStatus.CONFLICT).body("请勿重复提交");
    }

    // 执行业务逻辑
    formService.process(form);

    return ResponseEntity.ok("提交成功");
}