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From David Jencks <david_jen...@yahoo.com>
Subject Re: other appserver/ejb2.1 to geronimo 2.0 migration strategy?
Date Thu, 25 Jan 2007 08:23:45 GMT

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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