Hi, I am playing around with GWT, trying to implement a stateful client with a stateless server (IMO this is the paradigm shift proposed by the google guys). While this is a very promising solution for massive Web 2.0 ajax applications, I am running into some trouble handling this with cayenne (2.0.4).
Most of the application logic is handled by the GWT client. The servlet (GWT RPCService) is only used if the users change their settings or have to interact with each other. As there will be many users I don't want to have a session and associated datacontext per user. This would be very ineffective, since communication between client and server is reduced to a minimum. In addition, the datacontext stores objects in the objectstore to manage their states, this is not necessary in a stateless server scenario. Moreover, there are several isolated RPC services the users are interacting with. Hence, I decided to bind the context to a thread (see http://cayenne.apache.org/doc20/obtaining-datacontext.html). Each servlet handles a couple of threads automatically (in my case tomcat) and each thread has an own datacontext. This seems to be a nice solution as I don't face and tread-safety problems and don't need to care about sessions. The first thing when executing a method within a RPCService is to call a getcontext() method which gets the datacontext bounded to the thread (DataContext.getThreadDataContext()) or creates one (DataContext.bindThreadDataContext(DataContext.createDataContext(false))) if this is the first time this thread is executed by the servlet container. My only concern so far is the objectstore of the datacontext which keeps collecting objects. I set cayenne.DataRowStore.snapshot.size to 1 but this only affects the DataRowStore. I tried to use context.getObjectStore().startTrackingNewObjects() and then context.getObjectStore().unregisterNewObjects() every time i get the context from the thread but this does not solve my problem. IMO i don't need to track any objects in the objectStore. If a client calls a RPCService to create/change/delete something, this is either directly commited to the DB (context.commitChanges()) or rolled back in case of an error (context.rollbackChanges()). As the datacontext is kept per thread its objectstore will run full of data which will probably be never used again. Is there a way to clear the objectstore (expect calling unregisterNode() for each created object by hand)? Should I create a new datacontext for a thread after a while? Any ideas? Thanks in advance. Krzysztof
