20. 스프링 트랜잭션

// 1. A 계좌에서 출금
updateBalance(accountA, -10000);
// 2. B 계좌에 입금
updateBalance(accountB, +10000);

<!-- 트랜잭션 매니저 등록 -->
<bean id="transactionManager"
  class="org.springframework.jdbc
         .datasource
         .DataSourceTransactionManager">
    <property name="dataSource"
        ref="dataSource" />
</bean>

<!-- 애너테이션 기반 트랜잭션 활성화 -->
<tx:annotation-driven
    transaction-manager="transactionManager" />

@Service("orderService")
@Transactional
public class OrderServiceImpl
        implements OrderService {

    @Autowired
    private OrderDAO orderDAO;

    @Autowired
    private StockDAO stockDAO;

    @Override
    public void placeOrder(OrderVO order) {
        // 두 작업이 하나의 트랜잭션으로 묶임
        orderDAO.insertOrder(order);
        stockDAO.decreaseStock(
            order.getProductId(),
            order.getQuantity());
    }
}

// 로그는 별도 트랜잭션으로 저장
@Transactional(
    propagation = Propagation.REQUIRES_NEW)
public void saveLog(LogVO log) {
    logDAO.insertLog(log);
}

@Transactional(
    rollbackFor = Exception.class)
public void transferMoney(
        String from, String to, int amount)
        throws Exception {
    accountDAO.withdraw(from, amount);
    accountDAO.deposit(to, amount);
}

@Transactional(readOnly = true)
public List<MemberVO> getAllMembers() {
    return memberDAO.selectAllMembers();
}

@Service
public class MemberServiceImpl
        implements MemberService {

    // 트랜잭션 적용됨
    @Transactional
    public void methodA() {
        // 내부 호출 → 트랜잭션 미적용!
        methodB();
    }

    @Transactional(
        propagation = Propagation.REQUIRES_NEW)
    public void methodB() {
        // 새 트랜잭션이 시작되지 않는다
    }
}