Using the Domain Model pattern - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 80

3.3 Implementing a domain model: an example

In this section you will see an example of how the techniques described in the pre-
vious section can be used to develop a domain model. I show how to do this by
developing the methods that are called to handle the enter delivery information
request. I first implement the PlaceOrderService 's updateDeliveryInfo()
method we identified earlier. After that, I show how to implement a PendingOrder
method, which is called by updateDeliveryInfo() . The end result is working and
tested PlaceOrderService and PendingOrder methods that verify the delivery
information and update PendingOrder . The required repository methods are also
identified. By studying this small example, you will learn an effective way to
develop and test a domain model. Since the repository methods call the persis-
tence framework, we won't implement those until chapters 4-6.

3.3.1 Implementing a domain service method

PlaceOrderService , which is a domain model service, has an updateDelivery-
Info() method that is invoked when the user enters the delivery information.
This method has the following signature:

public interface PlaceOrderService {
PlaceOrderServiceResult updateDeliveryInfo(String pendingOrderId,
bbb Address deliveryAddress,
bbb Date deliveryTime);
}
Its parameters consist of pendingOrderId , which is the primary key of Pending-
Order in the database, and the deliveryAddress and deliveryTime parameters,
which specify the delivery information. It returns a PlaceOrderServiceResult ,
which consists of a status code and PendingOrder .
When updateDeliveryInfo() is invoked, PlaceOrderService retrieves Pending-
Order or creates one if it does not exist. It then does one of the following:

If the delivery time is in the future and the delivery information is served by
at least one restaurant, PlaceOrderService updates PendingOrder with the
new delivery information. It returns a PlaceOrderServiceResult containing
a successful status code and PendingOrder .

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If the delivery address and time are not served by any restaurant or the
delivery time is not in the future, PlaceOrderService leaves PendingOrder
unchanged. It returns a PlaceOrderServiceResult containing a status code
indicating failure and PendingOrder .

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