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| | | DAO relation with business object | DAO relation with business object 2004-06-21 - By Deblauwe, Wim
Back
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
Ing. Wim Deblauwe
Software Development Engineer
BarcoView - Medical Imaging Systems
Theodoor Sevenslaan 106
B-8500 Kortrijk, Belgium
Tel. +32 56 233 985 Fax +32 56 233 457
www.barco.com <http://www.barco.com/>
wim.deblauwe@(protected) <mailto:wim.deblauwe@(protected)>
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<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2>Hi,</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>I've looking at
the DAO pattern lately and have some problems with it. Especially what is ment
by Business Object and ValueObject?</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>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".</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>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.</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>Is this already
correct? Or is the business class something else and is my User class already a
ValueObject?</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>2nd
problem:</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>When I then create
my DAO, e.g. UserDAO. This would typically reside in the data package. There are
2 options then:</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>public User
getUser(int id);</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2>or</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>public ValueUser
getUser(id);</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>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.</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>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:</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>ValueUser
valueUser = new ValueUser();</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>valueUser.setName(
"testName" );</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>... some more
here</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>User user = new
User();</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2>user.setValueObject( valueUser );</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>assertEquals(
user.getName(), "testName" );</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>And I really don't
like this. You have to create 2 objects, where 1 should be
enough.</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana size=2>I hope the people
on this list can help me find some answers,</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2>bye,</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2>Wim</FONT></SPAN></DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=296160015-21062004><FONT face=Verdana
size=2></FONT></SPAN> </DIV>
<DIV class=Section1><FONT face=Arial size=2></FONT>
<P><BR><SPAN style="FONT-FAMILY: Arial"> </SPAN> <BR><B><SPAN
style="FONT-SIZE: 8pt; FONT-FAMILY: Verdana; mso-bidi-font-size: 7.5pt">Ing. Wim
Deblauwe</SPAN></B><SPAN style="FONT-SIZE: 8pt; mso-bidi-font-size: 12.0pt">
<BR></SPAN><SPAN
style="FONT-SIZE: 8pt; COLOR: gray; FONT-FAMILY: Verdana; mso-bidi-font-size: 7
.5pt">Software
Development Engineer</SPAN><SPAN
style="FONT-SIZE: 8pt; mso-bidi-font-size: 12.0pt"> <BR></SPAN><SPAN
style="FONT-SIZE: 8pt; FONT-FAMILY: Arial; mso-bidi-font-size: 12.0pt"> <
/SPAN><SPAN
style="FONT-SIZE: 8pt; mso-bidi-font-size: 12.0pt"> <BR></SPAN><SPAN
style="FONT-SIZE: 8pt; FONT-FAMILY: Verdana; mso-bidi-font-size: 7.5pt"
>BarcoView
- Medical Imaging Systems</SPAN><SPAN
style="FONT-SIZE: 8pt; mso-bidi-font-size: 12.0pt"> <BR></SPAN><SPAN
style="FONT-SIZE: 8pt; COLOR: gray; FONT-FAMILY: Verdana; mso-bidi-font-size: 7
.5pt">Theodoor
Sevenslaan 106</SPAN><SPAN style="FONT-SIZE: 8pt; mso-bidi-font-size: 12.0pt">
<BR></SPAN><SPAN
style="FONT-SIZE: 8pt; COLOR: gray; FONT-FAMILY: Verdana; mso-bidi-font-size: 7
.5pt">B-8500
Kortrijk, Belgium</SPAN><SPAN
style="FONT-SIZE: 8pt; mso-bidi-font-size: 12.0pt"> <BR></SPAN><SPAN
style="FONT-SIZE: 8pt; COLOR: gray; FONT-FAMILY: Verdana; mso-bidi-font-size: 7
.5pt">Tel.
+32 56 233 985 Fax +32 56 233 457</SPAN><SPAN
style="FONT-SIZE: 8pt; mso-bidi-font-size: 12.0pt"> <BR></SPAN><U><SPAN
style="FONT-SIZE: 8pt; COLOR: blue; FONT-FAMILY: Verdana; mso-bidi-font-size: 7
.5pt"><A
href="http://www.barco.com/">www.barco.com</A></SPAN></U><SPAN
style="FONT-SIZE: 8pt; mso-bidi-font-size: 12.0pt"> <BR></SPAN><U><SPAN
style="FONT-SIZE: 8pt; COLOR: blue; FONT-FAMILY: Verdana; mso-bidi-font-size: 7
.5pt"><A
href="mailto:wim.deblauwe@(protected)">wim.deblauwe@(protected)</A></SPAN></U></P><
/DIV>
<DIV> </DIV></BODY></HTML>
<P><I><FONT SIZE=2 FACE="Arial">- - - - - - - - DISCLAIMER - - - - - - - - <
/FONT></I></P>
<P><I><FONT SIZE=2 FACE="Arial">Unless indicated otherwise, the information
contained in this message is privileged and confidential, and is intended only
for the use of the addressee(s) named above and others who have been
specifically authorized to receive it. If you are not the intended recipient,
you are hereby notified that any dissemination, distribution or copying of this
message and/or attachments is strictly prohibited. The company accepts no
liability for any damage caused by any virus transmitted by this email.
Furthermore, the company does not warrant a proper and complete transmission of
this information, nor does it accept liability for any delays. If you have
received this message in error, please contact the sender and delete the
message. Thank you.</FONT></I></P>
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