transactional-patterns

Transactional Patterns

Basic Rules

• @Transactional belongs on service methods, never controllers or repositories
• Default propagation is REQUIRED — joins existing transaction or creates one
• Always use on methods that write to the DB or coordinate multiple writes
• @Transactional(readOnly = true) on all read-only service methods — enables optimizations

@Service
@RequiredArgsConstructor
@Transactional(readOnly = true) // default for all methods in this service
public class OrderService {

    @Transactional // overrides readOnly for writes
    public Order createOrder(CreateOrderRequest request) {
        inventoryService.reserve(request.items()); // participates in same TX
        return orderRepository.save(Order.from(request));
    }

    public Optional<Order> findById(UUID id) {
        return orderRepository.findById(id); // readOnly = true inherited
    }
}

Propagation

// REQUIRES_NEW — for audit logging that must survive rollback
@Transactional(propagation = Propagation.REQUIRES_NEW)
public void logAuditEvent(AuditEvent event) {
    auditRepository.save(event); // commits independently of parent TX
}

// Order TX rolls back, audit log still saved
@Transactional
public void processOrder(Order order) {
    auditService.logAuditEvent(new AuditEvent("ORDER_START", order.getId()));
    try {
        // ... process, may throw
    } catch (Exception e) {
        auditService.logAuditEvent(new AuditEvent("ORDER_FAILED", order.getId()));
        throw e; // parent TX rolls back, audit TX already committed
    }
}

Self-Invocation Pitfall

// ❌ BROKEN — self-invocation bypasses Spring proxy, @Transactional ignored
@Service
public class OrderService {
    @Transactional
    public void processAll(List<UUID> ids) {
        ids.forEach(id -> this.processSingle(id)); // bypasses proxy!
    }

    @Transactional(propagation = Propagation.REQUIRES_NEW)
    public void processSingle(UUID id) { ... } // never creates new TX
}

// ✅ FIX — inject self or extract to separate bean
@Service
@RequiredArgsConstructor
public class OrderService {
    private final OrderProcessor orderProcessor; // separate bean

    @Transactional
    public void processAll(List<UUID> ids) {
        ids.forEach(id -> orderProcessor.processSingle(id)); // goes through proxy
    }
}