簡介
在了解支付網關概述後，本文將深入探討支付處理流程－從授權到結算。這是最複雜的部分，需要絕對的精確，因為它與金錢直接相關。
1. 授權流程
1.1 卡授權
┌──────────┐ ┌──────────┐ ┌──────────┐ ┌──────────┐ ┌──────────┐
│ Customer │ │ Merchant │ │ Acquirer │ │ Card │ │ Issuer │
│ │ │ │ │ Bank │ │ Network │ │ Bank │
└────┬─────┘ └────┬─────┘ └────┬─────┘ └────┬─────┘ └────┬─────┘
│ │ │ │ │
│ Card Info │ │ │ │
├─────────────►│ │ │ │
│ │ Auth Req │ │ │
│ ├─────────────►│ │ │
│ │ │ Auth Req │ │
│ │ ├─────────────►│ │
│ │ │ │ Auth Req │
│ │ │ ├─────────────►│
│ │ │ │ │
│ │ │ │ Check: │
│ │ │ │ - Balance │
│ │ │ │ - Fraud │
│ │ │ │ - Limits │
│ │ │ │ │
│ │ │ │ Auth Resp │
│ │ │ │◄─────────────┤
│ │ │ Auth Resp │ │
│ │ │◄─────────────┤ │
│ │ Auth Resp │ │ │
│ │◄─────────────┤ │ │
│ Result │ │ │ │
│◄─────────────┤ │ │ │
1.2 授權回應碼
| 代碼 | 意義 | 行動 |
|---|---|---|
00 | 已核准 | 繼續捕獲 |
05 | 不尊重 | 終端機 - 不要重試 |
14 | 卡號無效 | 終端機 |
51 | 資金不足 | 終端 |
54 | 過期卡 | 終端機 |
61 | 超過限制 | 可以用較低的金額重試 |
91 | 發行人不詳 | 稍後重試 |
1.3 授權保留管理
Authorization creates a "hold" on customer funds:
Timeline:
Day 0: Auth $100 ──► Hold $100 on card
Day 1-7: Hold active, merchant can capture
Day 7+: Hold expires (auto-release by issuer)
Rules:
├── Auth hold duration varies by card network
│ ├── Visa: 7-30 days
│ ├── Mastercard: 7-30 days
│ └── NAPAS: Varies by issuer
├── Partial capture: Can capture <= auth amount
├── Multi-capture: Some networks support partial captures
└── Void: Cancel auth before capture (release hold)
2. 捕捉過程
2.1 捕獲策略
1. Auto-capture (immediate):
Auth ──► Immediate Capture
Use case: Digital goods, instant delivery
2. Manual capture (delayed):
Auth ──► Wait ──► Capture when ready
Use case: Physical goods (capture on ship)
3. Partial capture:
Auth $100 ──► Capture $80 (partial shipment)
Remaining $20 ──► Void or capture later
4. Multi-capture:
Auth $100 ──► Capture $50 ──► Capture $30 ──► Capture $20
Use case: Marketplace with multiple sellers
2.2 捕獲實現
public class CaptureService {
@Transactional
public CaptureResult capture(String paymentId, Money amount) {
var payment = paymentRepository.findById(paymentId)
.orElseThrow(() -> new PaymentNotFoundException(paymentId));
// Validate
if (payment.getStatus() != PaymentStatus.AUTHORIZED) {
throw new InvalidStateException("Payment must be AUTHORIZED");
}
if (amount.isGreaterThan(payment.remainingCapturable())) {
throw new AmountExceedsAuthException();
}
// Capture with PSP
var pspResult = pspAdapter.capture(payment, amount);
// Update payment
payment.capture(amount, pspResult);
paymentRepository.save(payment);
// Publish event
eventBus.publish(new PaymentCapturedEvent(payment, amount));
return CaptureResult.success(payment);
}
}
3. 結算流程
3.1 結算流程
Settlement = Transfer of actual funds from issuer to acquirer to merchant
Daily Settlement Cycle:
┌─────────────────────────────────────────────────────────┐
│ │
│ 23:00 Cut-off time │
│ │ │
│ ▼ │
│ Batch all captured transactions for the day │
│ │ │
│ ▼ │
│ Submit settlement file to acquirer/network │
│ │ │
│ ▼ │
│ T+1: Clearing (acquirer receives funds from network) │
│ │ │
│ ▼ │
│ T+1~T+3: Payout to merchant account │
│ │ │
│ ▼ │
│ Settlement complete │
│ │
└─────────────────────────────────────────────────────────┘
3.2 結算架構
┌─────────────────────────────────────────────────────────┐
│ SETTLEMENT ENGINE │
│ │
│ ┌──────────┐ ┌──────────┐ ┌──────────────────┐ │
│ │ Batch │ │ Fee │ │ Payout │ │
│ │ Builder │───►│ Engine │───►│ Calculator │ │
│ └──────────┘ └──────────┘ └────────┬─────────┘ │
│ │ │
│ ┌──────────┐ ┌──────────┐ ┌────────▼─────────┐ │
│ │ Report │◄───│Reconcile │◄───│ Transfer │ │
│ │ Generator│ │ Engine │ │ Executor │ │
│ └──────────┘ └──────────┘ └──────────────────┘ │
└─────────────────────────────────────────────────────────┘
3.3 費用計算
Transaction Amount: 1,000,000 VND
Fee Breakdown:
├── Interchange fee (issuer): 1.5% = 15,000 VND
├── Network fee (Visa/MC): 0.2% = 2,000 VND
├── Acquirer fee: 0.3% = 3,000 VND
├── Gateway fee (our platform): 0.5% = 5,000 VND
└── Total fees: 2.5% = 25,000 VND
Merchant receives: 975,000 VND
public record SettlementCalculation(
Money grossAmount,
Money interchangeFee,
Money networkFee,
Money acquirerFee,
Money platformFee,
Money netAmount
) {
public static SettlementCalculation calculate(
Payment payment, MerchantFeeConfig config) {
Money gross = payment.getCapturedAmount();
Money interchange = gross.multiply(config.interchangeRate());
Money network = gross.multiply(config.networkRate());
Money acquirer = gross.multiply(config.acquirerRate());
Money platform = gross.multiply(config.platformRate());
Money net = gross.subtract(interchange)
.subtract(network)
.subtract(acquirer)
.subtract(platform);
return new SettlementCalculation(
gross, interchange, network, acquirer, platform, net);
}
}
4. 批次處理
4.1 日終批次
@Scheduled(cron = "0 0 23 * * *") // 23:00 daily
public void runDailySettlement() {
var cutoffTime = LocalDateTime.now();
var transactions = paymentRepository
.findCapturedNotSettled(cutoffTime);
// Group by merchant
var byMerchant = transactions.stream()
.collect(Collectors.groupingBy(Payment::getMerchantId));
for (var entry : byMerchant.entrySet()) {
var merchantId = entry.getKey();
var payments = entry.getValue();
// Calculate settlement
var settlement = settlementService
.createSettlement(merchantId, payments);
// Generate settlement file
settlementFileGenerator.generate(settlement);
// Queue payout
payoutService.queuePayout(settlement);
}
}
4.2 即時結算
即時支付的新趨勢（VietQR、UPI）：
Traditional: Capture → T+1~T+3 Settlement
Real-time: Capture → Instant Settlement (< 30 seconds)
Real-time settlement requires:
├── Real-time clearing network (NAPAS for Vietnam)
├── Pre-funded settlement accounts
├── Real-time balance management
└── Instant notification to merchant
5. 退款處理
5.1 退款類型
Full Refund: Payment $100 → Refund $100
Partial Refund: Payment $100 → Refund $30 (keep $70)
Multiple Refund: Payment $100 → Refund $30 → Refund $20 → ... (total ≤ $100)
5.2 退款流程
@Transactional
public RefundResult processRefund(String paymentId, Money amount, String reason) {
var payment = paymentRepository.findById(paymentId)
.orElseThrow(() -> new PaymentNotFoundException(paymentId));
// Validate
if (!payment.isRefundable()) {
throw new PaymentNotRefundableException();
}
if (amount.isGreaterThan(payment.refundableAmount())) {
throw new RefundAmountExceedsException();
}
// Process refund with PSP
var pspResult = pspAdapter.refund(payment, amount);
// Create refund record
var refund = Refund.create(payment, amount, reason, pspResult);
refundRepository.save(refund);
// Update payment
payment.addRefund(refund);
paymentRepository.save(payment);
// Reverse ledger entries
eventBus.publish(new RefundProcessedEvent(refund));
return RefundResult.success(refund);
}
總結
付款處理是一個複雜的過程，包含許多步驟：
- 授權：儲備資金，驗證卡
- 捕獲：收集授權資金（立即或延遲）
- 結算：透過清算網絡實際轉移資金
- 退款：逆轉付款流程
關鍵原則：每一步的冪等性、狀態機的清晰度、每次更改的審計追蹤。
下一篇文章：多 PSP 整合 — 設計抽象層，將多個 PSP（VNPay、MoMo、Stripe）與智慧路由整合。