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)
