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DAO relation with business object

Deblauwe, Wim

2004-06-21


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 
wim.deblauwe@barco.com

 

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