+1
Florian
On 08/06/2011 20:11, Peter Monks wrote:
Yeah, though it sounds like it would be rare that anyone would actually
serialize / deserialize NuxeoSession's anyway (even if they were serializable),
so that might allow some simplifying assumptions?
Opening the discussion up to the wider audience - would anyone object if I were
to raise an enhancement request for
org.apache.chemistry.opencmis.client.api.Session to extend java.io.Serializable?
Cheers,
Peter
On Jun 8, 2011, at 9:14 am, Florent Guillaume wrote:
Hi Peter,
Yes that would probably work.
The responsibility for who will be closing the connection when it's
been restablished during deserialization is a bit muddy, but that's
another concern.
So if there's really a need to have Session be Serializable again, I
won't vote against it.
Florent
On Wed, Jun 8, 2011 at 5:42 PM, Peter Monks<[email protected]> wrote:
Thanks for the clarification Florent.
Question for you - if Session was Serializable, couldn't
org.nuxeo.ecm.core.opencmis.impl.client.NuxeoSession hold a transient reference to the
non-serializable objects, with the "connection" re-estalished automatically
post-deserialization? Presumably this would require some serialization of the session
parameters, but generally speaking those are fairly small / lightweight.
Cheers,
Peter
On Jun 8, 2011, at 8:11 am, Florent Guillaume wrote:
Hi Peter,
FYI, here's an example of non-Serializable Session implementation:
Nuxeo plugins can use OpenCMIS APIs directly in same-JVM mode (without
a networking layer being invoked), using
org.nuxeo.ecm.core.opencmis.impl.client.NuxeoSession. This
implementation of Session holds (indirectly) a reference to a
non-Serializable low-level connection-like object (think
java.sql.Connection), that by definition is not Serializable.
Florent
On Thu, Jun 2, 2011 at 9:21 PM, Peter Monks<[email protected]> wrote:
Thanks Florian. I'm still a little confused though - if Session is not
Serializable, how can I rely on an arbitrary Session implementation class being
Serializable? What if someone configures my client to use one of these
non-Chemistry Session implementations?
Possible workarounds include:
Checking whether the implementation class is an instanceof Serializable, and
not caching it if it isn't (which implies poor performance for Session
implementations that aren't serializable)
Wrapping Session in a Serializable wrapper that has a transient reference to
the Session (Session will be cached as long as it's kept in memory by the JVM -
as soon as the cache serializes a Session for whatever reason, that Session
will effectively become decached and incur the creation cost next time that
user does something that requires CMIS)
In the specific client I'm working on right now I can live with either workaround, but in
general (and imho) they are both quite undesirable given that this is likely to be a
common use case. I notice for example that the Liferay guys identified a need for
Session caching in their "CMIS Document Library" implementation (see [1], in
particular the comments). We can probably assume that either the Liferay cache doesn't
require items to be Serializable, or they worked around it in something like one of the
two ways described above.
Thinking along different lines for a moment - why does creating a Session have to hit the
CMIS server at all - is it to validate the username and password? If so, is it worth
delaying that check until the first "real" CMIS call, thereby significantly
reducing the cost of establishing a Session (i.e. by eliminating any RPCs to the CMIS
server at Session creation time)? This could even be configured via a flag to the
SessionFactory to preserve backwards compatibility.
Cheers,
Peter
[1] http://www.liferay.com/web/alexander.chow/blog/-/blogs/7670631
On Jun 2, 2011, at 2:26 am, Florian Müller wrote:
Hi Peter,
We had some discussions about that in the past. There are actually other
implementations of the OpenCMIS interfaces (not part of Apache Chemistry) that
can not and need not be serializable. We don't want to force them to do
something crazy just to implement the OpenCMIS interfaces.
The OpenCMIS classes have been designed to be serializable from the start to
support HTTP sessions. Casting to Serializable is safe now and will be safe in
the future -- even though it might feel weird.
What surprises me is that creating a session takes several seconds. Connecting
to a Alfresco server on a local network takes about 100ms. If it takes
significantly longer then there is something wrong...
Florian
On 01/06/2011 23:35, Peter Monks wrote:
G'day everyone,
Creating an org.apache.chemistry.opencmis.client.api.Session is quite an
expensive operation (it typically takes several seconds), so I'm looking to
cache Session objects in a per-user cache in my client app so that I don't have
to recreate Sessions for every single interaction with the CMIS server.
Unfortunately the cache library I'm using requires that cached objects
implement java.io.Serializable, which Session does not. However the default
implementation class (org.apache.chemistry.opencmis.client.runtime.SessionImpl)
does in fact implement Serializable, allowing me the workaround of casting the
Session object to Serializable prior to adding to the cache. I'm not
particularly comfortable with this approach however, given that this seems to
be an implementation detail and not officially part of the contract for
Sessions.
Is there a compelling reason that Session doesn't implement Serializable? Is
this something that could be added (noting that this change is backwards
compatible)?
Thanks in advance,
Peter
--
Florent Guillaume, Director of R&D, Nuxeo
Open Source, Java EE based, Enterprise Content Management (ECM)
http://www.nuxeo.com http://www.nuxeo.org +33 1 40 33 79 87
--
Florent Guillaume, Director of R&D, Nuxeo
Open Source, Java EE based, Enterprise Content Management (ECM)
http://www.nuxeo.com http://www.nuxeo.org +33 1 40 33 79 87
