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.

david jencks


what do you think about that?


Anybody already migrated large CMP/CMR apps to Geronimo?





virtually hanzz...


http://hanzz.zapto.org (personal)
http://www.cse.dmu.ac.uk/~hansp (research)