What is a "Data Object "? 2004-01-02 - By Chad Woolley
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Ashraf,
First, please ignore my previous message where I said you only posted the UML
diagram. Your text came across as an attachment and I couldn't read it in my
digest (which is in some unreadable mime format) or on sun's site. Plus, there
may be duplicates, because when I tried to post from the web form, the page hung
but the post still went through. That must have been what happened to you too.
This isn't a very impressive site for sun, they should just do it like Apache
's.
Anyway, thanks for your response. I've got some comments and questions, which I
included inline below.
ashraf galal wrote:
> Chad;
>
> It is the implementation of the business object pattern.
>
> Term: Business Object:
>
> An object that implements business logic and/or business data.
>
> Business data and business logic are implemented in coarse-grained objects
called business objects.
>
> In J2EE, business objects are implemented as session or entity beans.
>
> In some cases, a business object could be an arbitrary java object that
provides some services.
> See attached document for class and sequence diagrams
>
> I do think that these diagrams must answer most of your questions.
>
> We might implement the business object using the composite entity pattern
(you are right) or DAO or other different implementation.
This code example is in the "Business Object" chapter, and the UML diagram you
attached is from the chapter. I would think they would call it "Business
Object" in the code sample if it is an occurence of that pattern. In other
places in the book, if a pattern uses itself "recursively", it uses the same
name.
Maybe that is the case, though. Maybe it is just a "simple" business object
that doesn't have much logic in it. It still doesn't make sense to call it
something different, though.
> Regarding your question �Can the Presentation Tier directly
> instantiate and use "Data Objects"? �
>
> We always use the business delegate pattern to decouple the tier and hide the
implementation details. It is better not to use it directly from client tier
(my opinion).
Now you lost me. How is this related to the Business Delegate pattern? if it
was used on the client, it would probably be passed through a Business Delegate,
but that doesn't tell me anything more about what a "Data Object" is or how it
is used.
Thanks for your response!
Chad
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