支付请求幂等性设计

CREATE TABLE payment_records (
    id BIGINT PRIMARY KEY AUTO_INCREMENT,
    request_id VARCHAR(64) UNIQUE NOT NULL,
    order_no VARCHAR(32) NOT NULL,
    merchant_id VARCHAR(32) NOT NULL,
    amount DECIMAL(15,2) NOT NULL,
    currency VARCHAR(3) DEFAULT 'CNY',
    payment_status VARCHAR(16) NOT NULL,
    create_time DATETIME NOT NULL,
    update_time DATETIME NOT NULL,
    version INT DEFAULT 0,
    INDEX idx_request_id(request_id),
    INDEX idx_order_merchant(order_no, merchant_id)
);

public class PaymentIdempotentService {
    private static final String LOCK_PREFIX = "payment_lock:";
    private static final int LOCK_EXPIRE = 30;
    
    public boolean tryLock(String requestId) {
        String lockKey = LOCK_PREFIX + requestId;
        return redisTemplate.opsForValue()
            .setIfAbsent(lockKey, "1", Duration.ofSeconds(LOCK_EXPIRE));
    }
    
    public void releaseLock(String requestId) {
        String lockKey = LOCK_PREFIX + requestId;
        redisTemplate.delete(lockKey);
    }
}

@Service
public class PaymentProcessService {
    
    @Transactional(rollbackFor = Exception.class)
    public PaymentResult processPayment(PaymentRequest request) {
        // 1. 幂等性检查
        PaymentRecord existingRecord = checkIdempotent(request.getRequestId());
        if (existingRecord != null) {
            return buildResultFromRecord(existingRecord);
        }
        
        // 2. 获取分布式锁
        if (!idempotentService.tryLock(request.getRequestId())) {
            throw new BusinessException("支付请求正在处理中");
        }
        
        try {
            // 3. 创建支付记录
            PaymentRecord record = createPaymentRecord(request);
            
            // 4. 执行风控检查
            riskControlService.checkPaymentRisk(request);
            
            // 5. 调用支付通道
            PaymentChannelResponse channelResponse = 
                paymentChannelService.executePayment(request);
            
            // 6. 更新支付状态
            updatePaymentStatus(record, channelResponse);
            
            return buildSuccessResult(record, channelResponse);
            
        } finally {
            // 7. 释放分布式锁
            idempotentService.releaseLock(request.getRequestId());
        }
    }
}