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:[EMAIL PROTECTED]
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
===========================
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http://hanzz.zapto.org (personal)
http://www.cse.dmu.ac.uk/~hansp (research)
