Well - that's a really interesting question. Certainly JPA could be scala-fied somehow, but that's not the reason I don't use it any more (I have nothing against annotations even if they sometimes look a bit awkward in Scala). The reason I look for other alternatives now is that JPA pretty much totally relies on mutable state (vars rather than vals) - the fields are all filled in after initial instance creation. Squeryl and other options in Scala opt for a more idiomatic immutable model (although you can make them mutable if you want), so everything ends up as vals or (often more usefully) lazy vals, even the results of relationships.
This does take a little getting used to, the "new" way often involves making a database update through a DSL expression (like a SQL update statement, which leaves the original object intact and just changes the data in the database), and then re-querying the object to get it in its new state, rather than just updating fields and saving the new object. It's a trade-off I willingly make though for the extra safety and consistency of handling only immutable instances in my programs. It ends up being a bit like a database enforced STM. Another advantage is you can easily disconnect these objects from the database and hold them as simple in-memory representations, getting a ton of performance improvement by dropping all of the semaphors for updates, dirty caches, etc. If you need the most recent version of the object, requery it and get on with life. All of this suits databases with lower write and higher read ratios, but fortunately that's what I tend to work on. On Jun 15, 7:07 am, Jan Goyvaerts <java.arti...@gmail.com> wrote: > No problem. We're not getting any younger, are we ? ;-) > > If I'm not mistaken it was one of the things about Scala being appreciated > by Java developers. Because it felt more natural to do this in Scala. > Something like that anyway. But I'll have to listening again to make sure. > > Traits ? Is it enough to add a trait to a class to make it JPA compliant ? > > > > > > > > On Wed, Jun 15, 2011 at 15:47, Dick Wall <dickw...@gmail.com> wrote: > > Gosh - Sorry Jan, I have absolutely no recollection of saying that, > > can someone give me a hint what my train of thought might have been. > > > I don't use JPA in Scala, as much as I liked it in Java. I use > > Squeryl, sometimes Querulous, and MongoDB whenever I can. I think > > traits can be a more natural way of mixing in persistence to a class > > than annotations (perhaps that's what I was thinking), but beyond that > > I can't imagine what I would have been thinking at the time :-). > > > Dick > > > On Jun 15, 2:37 am, Jan Goyvaerts <java.arti...@gmail.com> wrote: > > > In the aforementioned episode Dick talks about Scala being > > natural/intuitive > > > for object persistence. I assumed he meant using JPA with case classes. > > But > > > did he meant it that way ? In the last week I had various trials with > > mixed > > > success. I'd rather have case classes for their advantages but then > > there's > > > the tricky formatting of the annotations. > > > > Does anybody in here have a working example/doc of these Scala-natural > > > entities ? (case classes ? all in one file ? etc ...) > > > > My biggest frustration : I can't get the 2nd level caching working. I've > > > done this many times in Java. But Scala code resisted all my attempts so > > > far. Does anybody in here managed to enable the 2nd level cache ? Please > > ... > > > :-P > > > > Thanks ! > > > > Jan > > > -- > > You received this message because you are subscribed to the Google Groups > > "The Java Posse" group. > > To post to this group, send email to javaposse@googlegroups.com. > > To unsubscribe from this group, send email to > > javaposse+unsubscr...@googlegroups.com. > > For more options, visit this group at > >http://groups.google.com/group/javaposse?hl=en. -- You received this message because you are subscribed to the Google Groups "The Java Posse" group. To post to this group, send email to javaposse@googlegroups.com. To unsubscribe from this group, send email to javaposse+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/javaposse?hl=en.
