I did more or less the same thing for the same reasons, and with the same happy result.The only difference for me was instead of annotations, I generate my model from an RDBMS. This way I know I can port my app to an RDBMS world should GAE ever go the same way as Google Notebook.
On Thu, Oct 22, 2009 at 11:43 AM, Richard <richard.wat...@gmail.com> wrote: > > Sounds good. I also think I'll focus much of my attention on the low- > level API, so this could be very useful! > > Regards, > Richard > > On Oct 22, 11:37 am, Nacho Coloma <icol...@gmail.com> wrote: > > Hi all, > > > > We have been developing a persistence framework for the AppEngine > > Datastore based on the raw DatastoreService API. For our (simple) > > persistence case, both JDO and JPA were a bit overkill as we were > > spending a significant amount of time jumping through hoops to make > > our application roll, but at the same time the Datastore API was a too > > low-level solution to be usable. > > > > So we reinvented our wheel. In two days. > > > > SimpleDS is a light wrapper around the DatastoreService APIs that > > provide a simple interface for java persistent classes. It does not > > include fancy stuff or any super features, it's just the > > DatastoreService ported to a world where Java entities can be > > persisted directly (using a subset of JPA annotations). This is _not_ > > a JPA/JDO replacement, and will never be. But we have been using it > > for some weeks and are quite happy with it. > > > > Any kind of feedback from the AppEngine community would be welcome. > > Before calling the typical "but we already have JPA/JDO!" argument, > > please notice the following: > > > > * There are lots of considerations in a relational database that do > > not apply to AppEngine. This allows a specific solution to be > > simplified big time. Just see the depth of your typical stack trace to > > understand what I am talking about. > > * Solutions can be designed for specific cases that are common > > practice in AppEngine but do not apply to a relational database. See, > > for example, saving entities with a parent instance. > > * Transactions also behave a bit differently, where a "one size fits > > all" approach would probably not be the best solution. > > > > To better ilustrate with an example, these are some typical tasks > > performed with SimpleDS: > > > > Retrieve instance: > > FooBar bar = entityManager.get(key); > > > > Transform from Google Datastore Entity to java and viceversa: > > Entity entity = entityManager.datastoreToJava(bar); > > > > Save generating a primary key, with a parent instance: > > FooBar bar = new FooBar(); > > entityManager.put(parentKey, bar); > > > > More can be seen here:http://code.google.com/p/simpleds/wiki/SimpleTasks > > > > Any discussion about the current API state is welcome. This entire > > thing was rolled in two days and tested in a couple of weeks so there > > should be some bugs in between. > > > > It is important to keep in mind the current list of limitations: > > > > * Only the Key class is a supported primary key. > > * IN and != are not supported (yet). I have big concerns about > > supporting this, performance-wise. > > * Relationships are not supported. You can use Keys and collections of > > Keys for that purpose. > > * Transactions are not yet included. We are not yet sure about how to > > proceed here. > > > > As I said, this is not conceived to become a feature-complete JPA > > replacement, so please don't treat it like that. > > > > Best regards, > > > > Nacho. > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To post to this group, send email to google-appengine-java@googlegroups.com To unsubscribe from this group, send email to google-appengine-java+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en -~----------~----~----~----~------~----~------~--~---
