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From "Jukka Zitting" <jukka.zitt...@gmail.com>
Subject Re: Where does JCR fit in JEE?
Date Thu, 26 Oct 2006 15:07:30 GMT

On 10/24/06, Srepfler Srgjan <srgjan.srepfler@lnksystem.com> wrote:
> I have implemented the DAO pattern so I can switch between
> persistence layers but to me it seems the two approaches are mutually
> exclusive. Can someone give me advice what's the best way to combine
> these two technologies and how to get the most of both worlds?

I generally prefer to expose the JCR Node/Property model all the way
up to the business and presentation logic. The way I see it, the DAO
pattern solves two different problems: it allows you to swap
persistence mechanisms and it hides the underlying data access API
behind a more natural OO API. The latter issue mostly affects cases
maps poorly to implementing common business or presentation logic
(JDBC). I find the JCR API quite natural to work with (compare
Node.getProperty(...) with the JDBC equivalent of executing a SELECT,
possibly caching the results over multiple calls, etc.) so from my
perspective the main reason for using the DAO pattern over JCR is when
you either need to use a persistence mechanism that doesn't support
JCR or to transparently support different JCR content models.

If you do need to apply the DAO pattern with JCR, I suggest you take a
look at the JCR Mapping tool in the Graffito project
(http://incubator.apache.org/graffito/). It's an object-to-content
mapping tool for JCR just like the various object-to-relational
mapping tools for JDBC.

> Second question, can I "butcher" jackrabbit in order to take out the core
> that handles the persistence stuff because I want to do all presentation
> stuff on my own (that is, is there a clean core module that I can
> integrate with my app)?

The Jackrabbit core (jackrabbit-core-1.1.jar) contains no presentation
logic. It should fit your needs pretty well.


Jukka Zitting

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