Using offline locking patterns - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 525

its responsibilities by calling various classes such as Order , OrderRepository , Pend-
ingOrder , and PendingOrderRepository . Each of its methods also calls the Lock-
Manager to acquire locks, to verify that locks are still held, and to release locks.
They pass the name of the Order class, order ID , and the caller as arguments to
the LockManager .

Listing 13.4 ModifyOrderServiceImpl

public class ModifyOrderServiceLockManagerImpl implements
ModifyOrderService {

private PendingOrderRepository pendingOrderRepository;

private OrderRepository orderRepository;

private LockManager lockManager;

private RestaurantRepository restaurantRepository;

B Creates
ModifyOrderServiceLock
ManagerImpl

public ModifyOrderServiceLockManagerImpl(
OrderRepository orderRepository,
PendingOrderRepository pendingOrderRepository,
RestaurantRepository restaurantRepository,
LockManager lockManager) {
this.pendingOrderRepository = pendingOrderRepository;
this.orderRepository = orderRepository;
this.restaurantRepository = restaurantRepository;
this.lockManager = lockManager;
}

public ModifyOrderServiceResult getOrderToModify(String caller,
String orderId) {
if (lockManager
.acquireLock(Order.class.getName(),
orderId,
caller)) {
Order order = orderRepository.findOrder(orderId);
PendingOrder pendingOrder =
createPendingOrder(order);
return new ModifyOrderServiceResult(
ModifyOrderServiceResult.OK,
pendingOrder);
} else {
return new ModifyOrderServiceResult(
ModifyOrderServiceResult.ALREADY_LOCKED);

C Locks
Order

D Creates
PendingOrder

E Returns
ModifyOrderServiceResult

}
}