DAO relation with business object

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DAO relation with business object

DAO relation with business object

2004-06-28 - By Deblauwe, Wim

Back

Reply: 1 2 3 4 5

Hmm... I wasn't aware of that second version of the book:
http://www.corej2eepatterns.com/Patterns2ndEd/DataAccessObject.htm

There seems to be no Business Object anymore like in
http://java.sun.com/blueprints/corej2eepatterns/Patterns/DataAccessObject.ht
ml

I hope the authors of these books are on this list, maybe they can answer
these questions for us ;)

regards,

Wim

-- --Original Message-- --
From: An interest list for Sun Java Center J2EE Pattern Catalog
[mailto:J2EEPATTERNS-INTEREST@(protected)]On Behalf Of Chad Woolley
Sent: zaterdag 26 juni 2004 21:56
To: J2EEPATTERNS-INTEREST@(protected)
Subject: Re: DAO relation with business object

Wim,

Check out my thread in the archives of this list called "What is a Data
Object?":

http://archives.java.sun.com/cgi-bin/wa?A1=ind0401&L=j2eepatterns-interest&D
=0#14

In my opinion, when they upgraded the book for the second edition, they left
some subtle but big holes in explaining just what is a "Data Object",
"Transfer
Object", "Value Object" (which is apparently replaced by Transfer Object but
still referenced in the second edition index), and "Business Object".

In addition to the thread (for which I never got a satisfactory answer),
emails
to the authors got no response...

Also, it will be interesting to see how the "Core J2EE Patterns" evolve with
the
apparent direction of the EJB spec towards supporting "Dependency
Injection". I
would think that it would result in some major changes to these patterns :)

Good Luck,
Chad

"Deblauwe, Wim" <wim.deblauwe@(protected)> wrote:
> Hi,
>
> I've looking at the DAO pattern lately and have some problems with it.
> Especially what is ment by Business Object and ValueObject?
>
> In my words I would call a class User that is a POJO a Business Object,
and
> I would place it in a package "business".
>
> I would then have a class ValueUser in my data package that has all the
same
> methods as business.User. In fact, business.User is just a delegate to
> data.ValueUser.
>
> Is this already correct? Or is the business class something else and is my
> User class already a ValueObject?
>
> 2nd problem:
> When I then create my DAO, e.g. UserDAO. This would typically reside in
the
> data package. There are 2 options then:
>
> public User getUser(int id);
>
> or
>
> public ValueUser getUser(id);
>
> If my business.User class is already a ValueObject, then a class from my
> data-layer is dependant on a class from my business-layer. This would be
> undesirable I think.
> Otherwise we refer to the ValueUser which is in the same layer, so this
> seems ok. But when you try to unit-test User when it is just a delegate
for
> ValueUser, you will do this:
>
> ValueUser valueUser = new ValueUser();
> valueUser.setName( "testName" );
> ... some more here
>
> User user = new User();
> user.setValueObject( valueUser );
>
> assertEquals( user.getName(), "testName" );
>
> And I really don't like this. You have to create 2 objects, where 1 should
> be enough.
>
>
> I hope the people on this list can help me find some answers,
>
> bye,
>
> Wim

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Hmm... I wasn't aware of that second version of the book:
 <A HREF="http://www.corej2eepatterns.com/Patterns2ndEd
/DataAccessObject.htm" TARGET="_blank">http://www.corej2eepatterns.com
/Patterns2ndEd/DataAccessObject.htm</A>


There seems to be no Business Object anymore like in <A HREF=
"http://java.sun.com/blueprints/corej2eepatterns/Patterns/DataAccessObject.html"
TARGET="_blank">http://java.sun.com/blueprints/corej2eepatterns/Patterns
/DataAccessObject.html</A>

I hope the authors of these books are on this list, maybe they
can answer these questions for us ;)


regards,


Wim


-- --Original Message-- --
 From: An interest list for Sun Java Center J2EE Pattern
Catalog
 [<A HREF="mailto:J2EEPATTERNS-INTEREST@(protected)">mailto
:J2EEPATTERNS-INTEREST@(protected)</A>]On Behalf Of Chad Woolley
 Sent: zaterdag 26 juni 2004 21:56
 To: J2EEPATTERNS-INTEREST@(protected)
 Subject: Re: DAO relation with business object

 

Wim,


Check out my thread in the archives of this list called &quot
;What is a Data Object?":


<A HREF="http://archives.java.sun.com/cgi-bin/wa?A1=ind0401&L
=j2eepatterns-interest&D=0#14" TARGET="_blank">http://archives.java.sun.com/cgi
-bin/wa?A1=ind0401&L=j2eepatterns-interest&D=0#14</A>


In my opinion, when they upgraded the book for the second
edition, they left
 some subtle but big holes in explaining just what is a &quot
;Data Object", "Transfer
 Object", "Value Object" (which is apparently
replaced by Transfer Object but
 still referenced in the second edition index), and &quot
;Business Object".


In addition to the thread (for which I never got a satisfactory
answer), emails
 to the authors got no response...


Also, it will be interesting to see how the "Core J2EE
Patterns" evolve with the
 apparent direction of the EJB spec towards supporting &quot
;Dependency Injection".  I
 would think that it would result in some major changes to
these patterns :)


Good Luck,
 Chad

 

"Deblauwe, Wim" <wim.deblauwe@(protected)> wrote:

 > Hi,
 >
 > I've looking at the DAO pattern lately and have some
problems with it.
 > Especially what is ment by Business Object and
ValueObject?
 >
 > In my words I would call a class User that is a POJO a
Business Object, and
 > I would place it in a package "business".
 >
 > I would then have a class ValueUser in my data package
that has all the same
 > methods as business.User. In fact, business.User is just
a delegate to
 > data.ValueUser.
 >
 > Is this already correct? Or is the business class
something else and is my
 > User class already a ValueObject?
 >
 > 2nd problem:
 > When I then create my DAO, e.g. UserDAO. This would
typically reside in the
 > data package. There are 2 options then:
 >
 > public User getUser(int id);
 >
 > or
 >
 > public ValueUser getUser(id);
 >
 > If my business.User class is already a ValueObject, then
a class from my
 > data-layer is dependant on a class from my business-layer
. This would be
 > undesirable I think.
 > Otherwise we refer to the ValueUser which is in the same
layer, so this
 > seems ok. But when you try to unit-test User when it is
just a delegate for
 > ValueUser, you will do this:
 >
 > ValueUser valueUser = new ValueUser();
 > valueUser.setName( "testName" );
 > ... some more here
 >
 > User user = new User();
 > user.setValueObject( valueUser );
 >
 > assertEquals( user.getName(), "testName" );
 >
 > And I really don't like this. You have to create 2
objects, where 1 should
 > be enough.
 >
 >
 > I hope the people on this list can help me find some
answers,
 >
 > bye,
 >
 > Wim


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