Business Objects vs Data Objects [was Re: JXTemplates - what's in a name?]

[Derek Hohls <DH...@csir.co.za>]

Bertand

Is there not a difference between a Java "business
object" (which I assume in a Cocoon app will be a 
POJO - even though I do not now know where and
how to create this...) and "data access object" - at
least that what the Core J2EE patterns imply
http://java.sun.com/blueprints/corej2eepatterns/Patterns/DataAccessObject.html 

Is this distinction worth making?

Thanks
Derek

>>> bdelacretaz@apache.org 2004/05/05 02:43:31 PM >>>
Le 5 mai 04, à 14:35, Derek Hohls a écrit :

> Right - but I assuming its still handwritten code
> and not an existing module in Cocoon - is there
> a guide to how to integrate these into Cocoon?
> (I wont say "best practice"! ;-)

You should really get the supersonic block and look at the "bean 
editor" example application.
Although it doesn't access a database, it shows how Java objects (which 
could be DAOs) can be interfaced with a Cocoon application.

-Bertrand


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Re: Business Objects vs Data Objects [was Re: JXTemplates - what's in a name?]

[Bertrand Delacretaz <bd...@apache.org>]

Le 6 mai 04, à 09:44, Derek Hohls a écrit :

> Bertand
>
> Is there not a difference between a Java "business
> object" (which I assume in a Cocoon app will be a
> POJO - even though I do not now know where and
> how to create this...) and "data access object" - at
> least that what the Core J2EE patterns imply
> http://java.sun.com/blueprints/corej2eepatterns/Patterns/ 
> DataAccessObject.html

To be strict, yes: a DAO's role would be to interface with a database,  
save and retrieve data, that's it.

Whereas a "business object" usually means an object that sits on top of  
DAOs (or other data access methods) and implements business rules,  
aggregations, etc.

But I think this is not terribly important when talking about how to  
interface Cocoon with Java objects.

Basically, if you're using Flow as a front-end to business logic and/or  
data access stuff written in java, the Flow needs to:

1) Access the java objects
2) tell them to load the required data
3) manipulate the data (maybe with CForms) - the java objects are most  
often not used for this step
4) tell the java objects to save the modified data

That's it, and this is demonstrated (although in a very simple and  
limited way) by the bean editor app in the supersonic block.

The objects shown there do not use a database, the data is just being  
held in memory. But adding database load/save would happen only in the  
java world, without requiring further interaction with Flow (other than  
Flow calling the load/save methods at the right times).

Also, this example app uses a simple instantiation for 1), but if you  
really make your java objects play with the Cocoon framework, you'd  
want to use the Avalon object lookup mechanisms for this. It's a bit  
more complicated but not that much.

Hope this helps!

-Bertrand


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