Using offline locking patterns - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 524

which consists of the ModifyOrderService , ModifyOrderServiceImpl (which imple-
ments the ModifyOrderService interface), and the classes that it calls.In addition
to the ModifyOrderService and ModifyOrderServiceImpl , the design consists of
these other classes:
■ OrderRepository loads the Order .
■ PendingOrderRepository creates, loads, and deletes the PendingOrder .
■ LockManager maintains the locks in the database.
■ PendingOrder stores the changes made to the Order .
■ Order is the order being edited.

ModifyOrderResult is returned by the ModifyOrderService .

■

There are lots of details of the business logic that you do not need to know about
to understand how the Pessimistic Offline Lock pattern works, so we'll focus just
on the ModifyOrderService class and how it interacts with the lock manager. Check
out the online source code if you want to see the details of the other classes.
ModifyOrderService is an interface that specifies the methods that can be invoked
by the POJO façade or the presentation tier:

public interface ModifyOrderService {
public ModifyOrderServiceResult getOrderToModify(String caller,
String orderId);

public ModifyOrderServiceResult updateDeliveryInfo(
String caller, String orderId, String pendingOrderId,
Address deliveryAddress, Date deliveryTime);

public ModifyOrderServiceResult updateQuantities(String caller,
String orderId, String pendingOrderId, int[] quantities)
throws InvalidPendingOrderStateException;

public ModifyOrderServiceResult saveChangesToOrder(
String caller, String orderId, String pendingOrderId);

public ModifyOrderServiceResult cancelModifyOrder(
String caller, String orderId, String pendingOrderId);
}
Each method has a caller parameter, which is used as the lock owner. It could be
the HttpSession ID or the user ID . The other method parameters include the ID s
of orders and pending orders as well as values entered by the user, such as the
delivery time and the line item quantities.
The ModifyOrderService interface is implemented by the ModifyOrderServi-
ceImpl class, which is shown in listing 13.4. ModifyOrderServiceImpl fulfills