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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