DDD 在银行核心系统的落地实践

public class Voucher {
    private final VoucherId id;
    private final AccountingDate accountingDate;
    private final List<Entry> entries = new ArrayList<>();

    public void addEntry(AccountNo account, Direction direction, Money amount) {
        if (amount.isNotPositive()) {
            throw new DomainException("分录金额必须为正数");
        }
        entries.add(new Entry(account, direction, amount));
    }

    /** 记账前的唯一硬约束：借贷平衡 */
    public void post() {
        Money debit = sumOf(Direction.DEBIT);
        Money credit = sumOf(Direction.CREDIT);
        if (!debit.equals(credit)) {
            throw new DomainException(
                "借贷不平衡: debit=" + debit + ", credit=" + credit);
        }
        registerEvent(new VoucherPosted(id, accountingDate, entries));
    }
}

public final class Money {
    private final BigDecimal amount;
    private final Currency currency;

    public Money add(Money other) {
        requireSameCurrency(other);
        return new Money(amount.add(other.amount), currency);
    }

    private void requireSameCurrency(Money other) {
        if (!currency.equals(other.currency)) {
            throw new DomainException("币种不一致，禁止直接运算");
        }
    }

    /** 计息场景统一按产品配置的舍入规则收敛 */
    public Money scaleBy(RoundingRule rule) {
        return new Money(rule.apply(amount), currency);
    }
}

@Component
public class LegacyAccountAdapter implements AccountQueryPort {

    private final LegacyCoreClient client;

    @Override
    public AccountSnapshot query(AccountNo accountNo) {
        LegacyAcctResp resp = client.queryAcct(accountNo.value());
        // 老系统 STATFLG: 0 正常 1 冻结 2 睡眠 9 销户
        AccountStatus status = switch (resp.getStatFlg()) {
            case "0" -> AccountStatus.ACTIVE;
            case "1" -> AccountStatus.FROZEN;
            case "2" -> AccountStatus.DORMANT;
            case "9" -> AccountStatus.CLOSED;
            default -> throw new IntegrationException(
                "未知账户状态: " + resp.getStatFlg());
        };
        return new AccountSnapshot(accountNo, status,
                Money.of(resp.getBalance(), resp.getCcy()));
    }
}

#!/usr/bin/env bash
# 日终核对新老账务余额，差异写入待处理表
ACCT_DATE=${1:-$(date -d "yesterday" +%Y%m%d)}

mysql -h "$NEW_CORE_HOST" -N -e "
  SELECT account_no, balance FROM acct_balance
   WHERE accounting_date = '${ACCT_DATE}' ORDER BY account_no" > /tmp/new.txt

legacy_export --date "${ACCT_DATE}" --field acct,bal > /tmp/old.txt

if ! diff -q /tmp/new.txt /tmp/old.txt > /dev/null; then
  diff /tmp/new.txt /tmp/old.txt | recon-loader --date "${ACCT_DATE}"
  echo "[WARN] ${ACCT_DATE} 存在余额差异，已入待处理表"
  exit 1
fi
echo "[OK] ${ACCT_DATE} 新老账务一致"