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From Florian Müller <f...@apache.org>
Subject Re: Chunked transfer encoding
Date Fri, 10 May 2013 16:32:44 GMT
Hi Carlo,

I understand what you are saying. But there are no objects here. My 
first version of this servlet had all methods (that were implemented at 
that time) in the servlet class. The original idea of the Dispatcher was 
only to move the code out of the servlet class.

But let me play with a few things here. I'll get back to you.


- Florian


> Hi Florian,
>
> the core of my change isn't in the Dispatcher itself. Discarding final
> classes, private constructors and static methods is the main objective
> of that change, as it basically enable class inheritance. Pluggability
> of different behavior can indeed be achieved by exposing the Dispatcher,
> but it would still be using the reflection over static methods combo as
> before, which alone breaks four out of five features of OO
> <http://en.wikipedia.org/wiki/Object-oriented_programming>[1].
>
> On the runtime efficiency, I'd be happy to store some 100 more class
> definition if that will spare some CPU cycles due to reflection. We're
> talking of one-off tiny memory allocation VS tiny performance
> degradation per every single call here.
>
> c.
>
> [1] please don't take me for an OO fanatic, I'm much more of a FP guy
> these days. I just think that OO is better than procedural, especially
> on an OO platforms such as Java
>
>
> 2013/5/10 Florian Müller <fmui@apache.org <mailto:fmui@apache.org>>
>
>     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
>         <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<carlo.sciolla@gmail.__com
>         <mailto:carlo.sciolla@gmail.com>>
>
>             Hi Florian,
>
>             will do, I'll hopefully have a patch for you to review next
>             week.
>
>             c.
>
>
>             2013/5/10 Florian Müller<fmui@apache.org
>             <mailto:fmui@apache.org>>
>
>                 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<fmui@apache.org
>                     <mailto:fmui@apache.org>>
>
>                        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<
>                         carlo.sciolla@gmail.com
>                         <mailto:carlo.sciolla@gmail.com>>:
>
>                            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<fmui@apache.org
>                             <mailto:fmui@apache.org>>
>
>                                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<fmui@apache.org
>                                     <mailto:fmui@apache.org>>
>
>                                        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/******><https://issues.apache.__org/****
>                                         <https://issues.apache.org/****>>
>
>                                         jira/browse/CMIS-655<https://*__*issues.apache.org/**jira/**
>                                         <http://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><http:/__/issues.apache.org/jira/__browse/**CMIS-655
>                                         <http://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
>
>             --==(A)==--
>             Linux User #372086
>             My personal blog: http://www.skuro.tk
>             Follow me on twitter: http://twitter.com/skuro
>             <http://twitter.com/skuro>Fork me on Github:
>             http://github.com/skuro
>             <http://github.com/skuro>My LinkedIn profile:
>             http://nl.linkedin.com/in/__carlosciolla
>             <http://nl.linkedin.com/in/carlosciolla>
>             --==(A)==--
>
>             Product Lead at Backbase - Next Generation Portal Software
>             for Financials
>             &  Large Enterprises (http://www.backbase.com)
>
>
>
>
>
>
>
>
> --
> Carlo Sciolla
>
> --==(A)==--
> Linux User #372086
> My personal blog: http://www.skuro.tk
> Follow me on twitter: http://twitter.com/skuro
> <http://twitter.com/skuro>Fork me on Github: http://github.com/skuro
> <http://github.com/skuro>My LinkedIn profile:
> http://nl.linkedin.com/in/carlosciolla
> --==(A)==--
>
> Product Lead at Backbase - Next Generation Portal Software for
> Financials & Large Enterprises (http://www.backbase.com)


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