Sorry, I meant 3.0M4.
When getting a new DataContext on every request, you bypass one level
of caching, but in your situation this may actually be what you want.
Andrus
On Aug 27, 2008, at 3:43 PM, Krzysztof Janowicz wrote:
Hi Andrus,
thanks for the reply. Isn't creating a new context per request very
ineffective (see
http://cayenne.apache.org/doc/obtaining-datacontext.html)? Cayenne
3.0M5
is the version from SVN (or a nightly build), right? I will try this
one, thanks again.
Krzysztof
Andrus Adamchik schrieb:
Hi Krzysztof,
You can switch to Cayenne 3.0M5. It uses weak references and will
prevent objects in the ObjectStore from accumulating. Or throw away
the context at the end of the request or after N requests.
Andrus
On Aug 27, 2008, at 2:23 PM, Krzysztof Janowicz wrote:
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
