Got it. I thought you were heading in a different direction.
How is that different from making the current Dispatch object protected
or adding a protected method that wraps the Dispatch.addResource() method?
Extensibility-wise they would be equal. Your version only adds a bit
more syntactic sugar. It would also need a bit more memory because we
would have to add about 100 additional classes (AtomPub + Browser) and
runtime objects.
- Florian
Is it next week already? :-)
Jokes apart, I had one hour to spare for this topic now that it's still
hot, and produced the patch you can see attached to
CMIS-656<https://issues.apache.org/jira/browse/CMIS-656>.
That's a translation of the current Chemistry dispatch logic to abandon
reflection, static methods, private constructors, and final classes.
The flow is quite the same as before, with the servlet initialization logic
registering the default bindings by adding concrete instances of a
ServiceCall interface into a local registry. At request serving time the
registered ServiceCall is retrieved and its service() method invoked. The
invocation logic is now a mere INVOKEINTERFACE JVM instruction instead of
the previous reflection trick (tiny performance improvement here).
Please note that the ServiceCall interface was already a hidden contract
that all service calls had to implement to be addressable by the Method
created by the Dispatcher.
As a last note, CmisAtomPubServlet also exposes a protected
registerDispatch(resource, method, ServiceCall) to allow implementors to
override the default logic.
That's it for now. Please note that as the Dispatcher is shared across the
AtomPub and Browser bindings, and as only the AtomPub was properly
refactored, that patch will break your build.
Looking forward to hear your comments,
c.
2013/5/10 Carlo Sciolla<[email protected]>
Hi Florian,
will do, I'll hopefully have a patch for you to review next week.
c.
2013/5/10 Florian Müller<[email protected]>
Hi Carlo,
Please go ahead and make a proposal. Submit a patch that sketches your
ideas. It doesn't have to be complete and running.
It's easier to talk about something concrete rather than discussing about
generic topics.
- Florian
Hi Florian,
it's not my intent to start a flame war, and we can continue offline if
you
want. To the interest of the list, I'll just write here some of the
reasons
behind my previous comment, and wait until I have some patch ready to
prove
my points before bothering you guys again with my ramblings.
I understand your remark on the spec compliance, and that interop is at
stake when you allow the protocol details to be modified. BUT...
- There's much more to HTTP than what CMIS specifies, and Chemistry is
currently in charge of handling the transport protocol on top of which
CMIS
expresses itself.
- No extensibility means that backporting of fixes might be a no-go. For
example, if I now upgrade Chemistry to the latest trunk my code doesn't
compile anymore. Subclassing would be the best way to integrate your
changes in the version I use, but that's not available to me.
- The CMIS spec is (hopefully!) not fixed and will evolve with time. OO
could help greatly e.g. to support different versions of the protocol
with
a single serve instance, which is painful to implement cleanly following
the current code approach.
- Spec extensions are not evil per se. While they might indeed break
interoperability, they're also a way to open the protocol itself to
experiments and eventually drive a community based evolution of it.
- Interop is not always the top priority. CMIS and Chemistry provide a
lot
of value OOTB, and I don't see why proprietary extensions should be
denied
by principle. Why shouldn't I have the possibility to write a custom
extension to improve e.g. content delivery capabilities
(getContentStreamByPath, anyone?), while still retaining full protocol
compliance for B2B data exchange?
If you made it to here, a big thank you for your patience.
Hope this helps,
c.
2013/5/8 Florian Müller<[email protected]>
Hi Carlo,
This code is not meant to be extensible. The CMIS standard is fixed.
There
will be no additional services or operations. Also, the semantics of the
parameters will not change or have to be changed. Any extensions would
bypass the specification, which would be a pain for clients and doesn't
help interoperability.
All methods that handle requests are stateless, isolated pieces of code.
OO doesn't help here. And the alternative to reflections would be a 120
lines if-statement. I can't see the advantage of that.
Also, this part is considered internal code and may change at any time.
OpenCMIS provides a lot of extensibility on the client side and keeping
the
interfaces compatible does hurt sometimes. I don't see a real use case
to
have that pain also on the server side. If there is something missing or
wrong, we usually fix it pretty quick - as you have seen.
Having said that, if you have a great idea how to refactor that code,
feel
free to provide a patch.
- Florian
Am Mittwoch, den 08.05.2013, 16:05 +0200 schrieb Carlo Sciolla<
[email protected]>:
Hi Florian,
thanks for your quick commit, I will experiment a bit with it and let
you
know what comes out of it. I do already have some initial comments
anyway:
- I see you only addressed the browser bindings implementation. While I
can
see the reason behind it, I think it won't hurt to also apply a similar
logic to the AtomPub binding
- as I'm stuck with v0.6.0, I'm looking into ways to backport or
integrate
your code in my app. The current logic for method dispatch in AtomPub
goes
against extensibility (and some object oriented design principles, IMO)
and
while for the time being I can work around it, would you guys consider
refactoring the dispatch logic to make use of non-final classes / no
reflection / public constructors?
Thanks,
c.
2013/5/8 Florian Müller<[email protected]>
Hi Carlo,
I've added some new code. There are now three interfaces that let you
control the server headers.
The ContentStream object that is returned by getContentStream() must
implement the interface(s) to trigger the behavior:
ContentLengthContentStream - Sets the Content-Length header and turns
chunking off.
LastModifiedContentStream - Sets the Last-Modified header and respects
the
If-Modified-Since header.
CacheHeaderContentStream - Sets the Cache-Control header, the Expires
header, and the ETag header and respects the If-None-Match header.
Please let me know if that works for you.
- Florian
Hi there, sorry for the late reply.
2013/5/7 Florian Müller<[email protected]>
That is surprising. Chunked encoding isn't really exotic.
Definitely, but browsers are always there to remind us that world
class
standards are nothing different from regional social conventions,
are
they?
Could you please open an Improvement issue and add a few details.
I'll
look into it.
Thanks, here it
is<https://issues.apache.org/******<https://issues.apache.org/****>
jira/browse/CMIS-655<https://**issues.apache.org/**jira/**
browse/CMIS-655<https://issues.apache.org/**jira/browse/CMIS-655>>
<https://**issues.apache.org/**jira/browse/**CMIS-655<http://issues.apache.org/jira/browse/**CMIS-655>
<https:/**/issues.apache.org/jira/**browse/CMIS-655<https://issues.apache.org/jira/browse/CMIS-655>
>.
--
Carlo Sciolla
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