wow, that is quite extended material, thanks for the link. I will study and come back.
sebastian 2009/11/20 Kevin Sutter <[email protected]> > Hi Sebastian, > I'm sorry to day that we don't have a cookbook on this Hibernate migration > exercise. I would highly suggest (beg?) that you take good notes during > this migration so that we can all learn from the experience. > > I'm assuming you are moving from Hibernate "classic", meaning pre-JPA > programming model. Otherwise known as the Hibernate Session programming > model. If you are actually on moving from Hibernate JPA to OpenJPA, then > the migration should be relatively straight forward. But, from the content > of your notes below, I believe you are migrating from "classic" to OpenJPA. > > To that end, a colleague of mine and myself have written a white paper [1] > outlining the common Hibernate "classic" programming model paradigms and > how > to best map them to OpenJPA. So, I would start with that white paper and > see it gets you started. > > Also, OpenJPA supports both Annotations and XML, so if you feel more > comfortable with the XML configuration approach, you could stick with that. > > I hope this helps. > Good luck and let us know how it goes! > Kevin > > [1] > > http://www.ibm.com/developerworks/websphere/techjournal/0708_vines/0708_vines.html > > On Fri, Nov 20, 2009 at 3:47 AM, Sebastian Wagner <[email protected] > >wrote: > > > hi, > > > > > > in follow up from a discussion on the Apache General List: > > > > > http://mail-archives.apache.org/mod_mbox/incubator-general/200911.mbox/%[email protected]%3e > > > > I have some quite basic questions about migrating a existing Project > using > > Hibernate to openJPA. > > > > We are using a Hibernate 3.4 + XDoclet2 to generate the HBM files. > > We don't use a Spring Managed Transaction Manager yet for handling the > > Session (but we should). > > We have a lot of HQL Statements in the Code. > > The project is: http://openmeetings.googlecode.com > > (For anybody interested the Sources are located into > > > > > http://openmeetings.googlecode.com/svn/trunk/singlewebapp/src/app/org/openmeetings/app/ > > ) > > And we are applying for Apache Incubation, so we have to get rid of > > Hibernate. > > > > What is your general advice on an easy way to migrate to openJPA? > > > > Writing the intermediate database description per object, you use > > annotations I guess? > > In what kind of Java-Structure do you Map Many-To-One relations? > > How do you handle Multi-Threaded Applications and Database Caches? In > > hibernate a very common problem is that you have problems with Objects > that > > are several times in the Cache but in different Threads. In that case a > > Session.flush does not really work as it only flushs one Thread. This can > > be > > solved in Hibernate by using a Spring managed Transaction Manager. What > is > > JPAs approach in that area? > > And finally => HQL Statements, I guess I have to rewrite them all, but is > > the openJPA *JPQL* very different from that? From what I have seen its > not > > that big Issue to refactor those statements to JPQL. > > > > And I have a lot more questions before I can finally decide on what is > the > > best and feasable way to migrate. > > But I am eager to learn ^^ so maybe somebody is eager to give us some > tipps > > > > I will try to study the docs, > > but i have not seen any kick-start example yet that covers the most of > > basic > > topics. Is there any sample that can be re-used? > > > > > > thanks a lot > > Sebastian Wagner > > > > -- > > Sebastian Wagner > > http://www.webbase-design.de > > http://openmeetings.googlecode.com > > http://www.laszlo-forum.de > > [email protected] > > > -- Sebastian Wagner http://www.webbase-design.de http://openmeetings.googlecode.com http://www.laszlo-forum.de [email protected]
