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From David Jencks <david_jen...@yahoo.com>
Subject Re: AW: other appserver/ejb2.1 to geronimo 2.0 migration strategy?
Date Thu, 25 Jan 2007 16:46:18 GMT

On Jan 25, 2007, at 1:47 AM, Hans J. Prueller wrote:

> David,
>
>
>
> thank you for your thoughts. You provided good entry points for me.  
> I mentioned hibernate specifically because
>
> we already are using hibernate and CMP in parallel within our  
> project (as CMP2.x sometimes does not fulfill all needs).
>
>
>
> targeting JPA instead of hibernate specifically is essential –thank  
> you for that.
>
>
>
> I also would like to do a one-by-one migration because I am afraid  
> if we would migrate the whole project at once,
>
> everything could collapse. Doing smaller steps provides more  
> control I think.

That's easy to understand :-).  However if you have entity beans with  
cmr can you still migrate them one by one or do you have to migrate  
the entire tree of objects?
>
>
> >> However this would mean that you would need to start by  
> generating the cmp2 mapping info.
>
>
>
> so this is what should to be contained in the Geronimo deployment  
> plan right? are deployment plans required also
>
> in Geronimo2 ? (I think there shouldn’t be any more “vendor”  
> specific DDs in Java EE 5). But for compatibility reasons
>
> with my EJB2.1 CMP beans I think I won’t come around to provide a  
> mapping file at all ;-)
I suspect that some plans will still be needed to specify things like  
datasource configuration.

I was wondering if it would be practical to run your app on geronimo  
while it was being converted: I suspect not because you would need to  
have the cmp2 mapping info in a form geronimo could understand, and  
producing that would probably be harder than migrating to jpa directly.

> I asked about XDoclet support for Geronimo some months ago, at that  
> point in time there was no usable version around.
>
> As Java 2 EE 1.4 requires Java 1.4 I cannot work with annotations  
> unless the whole app is migrated, so XDoclet would
>
> be of great help…?
I'm not understanding what you are saying here.  Geronimo 1.2 (not  
quite released yet) includes jpa support and runs on jdk 1.5 only but  
is (or will be) a j2ee 1.4 app server.  In particular the jpa  
annotations all work fine (with openjpa).

thanks
david jencks

>
>
> regards,
>
> Hans
>
>
>
> Von: David Jencks [mailto:david_jencks@yahoo.com]
> Gesendet: Donnerstag, 25. Jänner 2007 09:24
> An: user@geronimo.apache.org
> Betreff: Re: other appserver/ejb2.1 to geronimo 2.0 migration  
> strategy?
>
>
>
>
>
> On Jan 24, 2007, at 10:15 PM, Hans J. Prueller wrote:
>
>
>
>
> hi together,
>
>
>
> I have been working with the JOnAS Java 2 EE application server for  
> about 5 years now, meanwhile
>
> I have several projects, one of them is rather big already, it  
> contains about 60-70 EJB’s, two thirds
>
> of them are CMP/CMR’ed entity beans, the rest stateless session beans.
>
>
>
> I am thinking about migrating these projects to Geronimo for some  
> months now, and I decided to
>
> wait for the first Java EE 5 release of Geronimo (Geronimo 2) – as  
> it will be released within the
>
> near future I would be interested in which migration strategies you  
> could suggest?
>
>
>
> I think the most problematic part will be to migrate the ca. 50 CMP  
> entity beans, there are a lot
>
> of EJB-QL finders and all of those beans are inter-related with CMR.
>
>
>
> Currently I’m thinking of doing a “soft” migration, i.e. migrating  
> 1 by 1 of those EB’s within the
>
> currenty architecture from CMP to hibernate, and after that  
> performing the move to Geronimo (which will
>
> mean that then only the session beans will have to be migrated  
> which should be less problematic).
>
>
>
> First of all I would target JPA rather than Hibernate specifically.
>
>
>
> Second, IIUC Dain has reimplemented CMP2 in openejb3 so it is  
> backed by openjpa.  This should mean that you could migrate the  
> entity beans one at a time and have coherent caching between the  
> jpa pojos and cmp entity beans.  However this would mean that you  
> would need to start by generating the cmp2 mapping info.
>
>
>
> I converted daytrader from entity beans to jpa very quickly.  It  
> was fairly easy because there were already data objects that hold  
> (most of) the same data that the entity beans hold.  I just added  
> annotations to the data beans and added the relationships (that had  
> been left out of the data beans for some reason).  If your  
> application already has something like a pojo data model layer it  
> would probably be easiest to simply start annotating the data  
> classes and drop the entity beans.
>
>
>
> Daytrader is not quite a toy app but it's much smaller than your  
> application so my results may not map directly to your situation.
>
>
>
> thanks
>
> david jencks
>
>
>
>
>
>
> what do you think about that?
>
>
>
> Anybody already migrated large CMP/CMR apps to Geronimo?
>
>
>
> regards,
>
> Hans
>
>
>
> ===========================
> virtually hanzz...
>
>
>
> http://hanzz.zapto.org (personal)
> http://www.cse.dmu.ac.uk/~hansp (research)
>
>
>
>
>
>
>
>
>
>
>
>
>


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