What is a "Data Object "? 2003-12-30 - By Chad Woolley
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On page 387 of the 2nd edition, in Example 7.21 for the "Business
Object" pattern, there is the following code:
public class CustomerBO {
// CustomerData is a Data Object
private CustomerData customerData;
. . .
public CustomerBO(CustomerData customerData) {
. . .
this.customerData = customerData;
}
. . .
}
What is a "Data Object"?? It's not a Transfer Object, because the
design note at the end of the chapter on page 390 specifically states
that a Business Object should NOT wrap a Transfer Object. It's also
obviously not a Data ACCESS Object.
It CAN be a composite object (contain other Data Objects), because that
is how it is used in the example.
It looks like it is just a plain Value Object, except that Value Objects
no longer exist in the second edition (except for the typo references in
the index that weren't changed to Transfer Object).
Is this just an object that holds data? If so, where does it fit with
the other patterns? Is it encapsulated within the Business Tier, or can
it be exposed to the Presentation Tier? If so, is it meant to be
transferred within a TransferObject? Can the Presentation Tier directly
instantiate and use "Data Objects"?
Thanks,
Chad
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