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From Pavel Pervov <pmcfi...@gmail.com>
Subject Re: Question about the boot and classloading
Date Wed, 20 May 2009 07:02:35 GMT
Sure. I've posted from mobile, and my multitap betrayed me. Thanks, Mark.

2009/5/20, Mark Hindess <mark.hindess@googlemail.com>:
>
> In message <e0f125db0905190627l72e6894fuc6904e92f37c27d4@mail.gmail.com>,
> Pavel Pervov writes:
>>
>> Please, read this nice presentation [1] on osgi vs classic class loading.
>> [1]
>> http://www.martinliqert.com/events/WJAX2008-ClassloadingTypeVisibilityOSGi.pdf
>
> I assume you mean:
>
>
> http://www.martinlippert.org/events/WJAX2008-ClassloadingTypeVisibilityOSGi.pdf
>
> -Mark.
>
>> 2009/5/19, tian galaxy <harmonymail.ty@gmail.com>:
>> > XiaoFeng , Mark
>> > Thanks for your help ,very valuable to me.
>> > I think I need to research more on this .Much more complex than I
>> > thought
>> > previously.
>> >
>> >
>> > Regard
>> > Tian
>> >
>> > 2009/5/19 Xiao-Feng Li <xiaofeng.li@gmail.com>
>> >
>> >> On Tue, May 19, 2009 at 6:41 PM, Mark Hindess
>> >> <mark.hindess@googlemail.com> wrote:
>> >> >
>> >> > In message
>> >> > <dff214c70905190147x57135ef3hf26cbf6a93ae2255@mail.gmail.com>,
>> >> tian
>> >> > galaxy writes:
>> >> >>
>> >> >> Hindess .Thanks for the help ! I realized that this far more complex
>> >> than I
>> >> >> thought before .
>> >> >> So I think I need a deeper look into both osgi and harmony .
>> >> >> Here are several things I don't qiute understand and I noted them
>> >> below.May
>> >> >> be it's because I am not quite familiar with the low level ,
>> >> classloading
>> >> >> details .
>> >> >> thanks!
>> >> >>
>> >> >> 2009/5/19 Mark Hindess <mark.hindess@googlemail.com>
>> >> >> >
>> >> >> > In message <
>> >> dff214c70905180610w407e3bd4h5baa319729c1fc55@mail.gmail.com>,
>> >> >> > tian galaxy writes:
>> >> >> > >
>> >> >> > > OK ,thanks .Seems the minimal class set has been defined
by the
>> >> osgi.
>> >> >> >
>> >> >> > Not sure how this helps though.  The OSGi Minimum Execution
>> >> Environment
>> >> >> > says what is theoretically the minimum required to run OSGi.
 What
>> >> >> > we
>> >> >> > need to concern ourselves with is the *practical* minimum
and that
>> >> >> > really depends on our implementation details.
>> >> >> >
>> >> >> > I don't think that we should implement OSGi in the VM.  Instead
>> >> >> > the
>> >> >> > existing bootstrap classloader should load the OSGi framework
>> >> >> > (with
>> >> >> > a unique classloader)
>> >> >>
>> >> >> If we load the osgi with the bootstrap class loader , why comes
a
>> >> >> unique
>> >> >> class loader?
>> >> >
>> >> > It isn't necessary but I think it is useful to use a separate
>> >> > classloader for the OSGi framework so that we can isolate the classes
>> >> > use by the VM's OSGi framework and avoid polluting the namespace.
>> >> >
>> >> >> Do you mean the bootstrap class loader should delegate the loading
>> >> >> to
>> >> >> the 'unique class loader '?
>> >> >
>> >> > Yes.
>> >> >
>> >> >> > and the system classes (with a "temporary" classloader).
>> >> >>
>> >> >> Again ,the relation between temporary and bootstrap classloder?
 And
>> >> >> why temporary ?
>> >> >
>> >> > Temporary because until the OSGi framework is up you wont know which
>> >> > bundle the classes belong to and thus wont know which bundle
>> >> > classloader
>> >> > the classes should belong to.  Alternatively, I suppose you could
>> >> > implement minimal support for reading OSGi headers from manifests
>> >> > in the VM so that you could assign classes to what would become a
>> >> > bundle
>> >> > classloader when the framework is up.
>> >> >
>> >> > -Mark.
>> >>
>> >>
>> >> This makes sense to me. The VM simply grabs in all the stuff "as
>> >> usual" including the OSGi framework, then sort them out according to
>> >> the bundles' definitions.
>> >>
>> >> It could be VM-neutral, because it is the VM's own business to take
>> >> care of its loaded classes. A callback interface OSGI_ready() can
>> >> inform the VM to tidy up the classes loaded for OSGi (or before it is
>> >> ready).
>> >>
>> >> Thanks,
>> >> xiaofeng
>> >>
>> >>
>> >> >> >  Once the OSGi framework is configured the system classes
need to
>> >> >> > be
>> >> >> > moved to the correct classloader for the OSGi bundle to which
they
>> >> >> > belong.
>> >> >> >
>> >> >> > This means that during the initial starting-OSGi-framework
phase
>> >> >> > the OSGi bundle import/exports will not be enforced but, other
>> >> >> > than
>> >> >> > implementing OSGi in the VM, I don't see how to avoid this.
>> >> >> >
>> >> >> > The multiplicity of bootstrap classloaders still needs to
be
>> >> >> > hidden
>> >> >> > since the API demands that getClassLoader should return null
for
>> >> >> > the
>> >> >> > bootstrap classloader(s).
>> >> >> >
>> >> >> > The biggest problem is probably how to implement this as
>> >> VM-independent
>> >> >> > API such that a VM wanting to implement OSGi had to provide
only a
>> >> >> > minimal C/Java interface in order to gain OSGi support.
>> >> >> >
>> >> >> > Regards,
>> >> >> >  Mark.
>> >> >> >
>> >> >> > > I will look more closely on this problems and let you
know if
>> >> >> > > there
>> >> some
>> >> >> > > progresses made.
>> >> >> > > Thanks  a  lot !
>> >> >> >
>> >> >> > > 2009/5/18 Pavel Pervov <pmcfirst@gmail.com>
>> >> >> > >
>> >> >> > > > I do not know osgi model in detail, but what minimal
set of
>> >> classes is
>> >> >> > > > needed to start osgi model itself? Then we could
delegate to
>> >> "system"
>> >> >> > > > bundle loader from bootstrap classloader.
>> >> >> > > >
>> >> >> > > > 2009/5/18, tian galaxy <harmonymail.ty@gmail.com>:
>> >> >> > > > > Yes , implement osgi loading model in there
is too complex.
>> >> >> > > > >
>> >> >> > > > > We know some modules are more important than
others ,
>> >> >> > > > > performing
>> >> some
>> >> >> > > > > fundamental , basic functions .
>> >> >> > > > > Is it possible to only load these more" basic
" modules with
>> >> >> > bootstrap
>> >> >> > > > class
>> >> >> > > > > loader and make the other modules work the
osgi bundle?
>> >> >> > > > > Actually I don't quite understand why system
classes could
>> >> >> > > > > only
>> >> be
>> >> >> > loaded
>> >> >> > > > by
>> >> >> > > > > bootstrap class loader?I noticed that there
are some safety
>> >> concerns
>> >> >> > > > > ,is there any reasons other than that?
>> >> >> > > > > Thanks !
>> >> >> > > > >
>> >> >> > > > >
>> >> >> > > > > 2009/5/18 Pavel Pervov <pmcfirst@gmail.com>
>> >> >> > > > >
>> >> >> > > > >> Short answer is "no". You'll have to implement
osgi loading
>> >> model
>> >> >> > > > >> inside bootstrap classloader. Is it too
complex?
>> >> >> > > > >>
>> >> >> > > > >> 2009/5/18, tian galaxy <harmonymail.ty@gmail.com>:
>> >> >> > > > >> > Hi Pavel.
>> >> >> > > > >> >
>> >> >> > > > >> > Thanks.
>> >> >> > > > >> > Yes ,that's right .My question is
whether there is a way
>> >> >> > > > >> > to
>> >> load
>> >> >> > the
>> >> >> > > > >> system
>> >> >> > > > >> > class by class loader other than the
 bootstrap class
>> >> >> > > > >> > loader
>> >> ?
>> >> >> > > > >> > If we could load the system class
by different loaders
>> >> >> > > > >> > other
>> >> than
>> >> >> > the
>> >> >> > > > >> > bootstrap class loader then there
is a chance to make the
>> >> harmony
>> >> >> > > > >> > runtime
>> >> >> > > > >> to
>> >> >> > > > >> > be osgi-ed.
>> >> >> > > > >> > I trying to work on this problem .
Do you have any
>> >> suggestions ?
>> >> >> > > > >> >
>> >> >> > > > >> >
>> >> >> > > > >> > 2009/5/18 Pavel Pervov <pmcfirst@gmail.com>
>> >> >> > > > >> >
>> >> >> > > > >> >> Tian,
>> >> >> > > > >> >> System classes are all loaded
with bootstrap
>> >> >> > > > >> >> classloader.
>> >> >> > > > >> >> It
>> >> is
>> >> >> > > > >> >> written in C++ and is located
in
>> >> >> > > > >> >> working_vm/vm/vmcore/src/class_support/classloader.cpp
>> >> >> > > > >> >>
>> >> >> > > > >> >> 2009/5/17, tian galaxy <harmonymail.ty@gmail.com>:
>> >> >> > > > >> >> > Hi all
>> >> >> > > > >> >> > I have a question about the
classloading in the drlvm.
>> >> >> > > > >> >> >
>> >> >> > > > >> >> > I know that there are kernel
library inside the drlvm
>> >> >> > > > >> >> > such
>> >> as
>> >> >> > > > >> >> > java.lang.classloader, which
enclose the the
>> >> systemclassloader.
>> >> >> > And
>> >> >> > > > >> this
>> >> >> > > > >> >> > class is loaded and used
in the process of creating VM
>> >> >> > > > >> >> > .
>> >> >> > > > >> >> > While the systemclassloader
is a subtype of
>> >> >> > > > >> >> > urlclassloader
>> >> >> > which is
>> >> >> > > > >> >> > in
>> >> >> > > > >> >> the
>> >> >> > > > >> >> > "luni" module.So does the
JNI_CreateJavaVM
>> >> >> > > > >> >> > also load the urlclassloader
in the boot procedure of
>> >> >> > > > >> >> > vm
>> >> ?(I
>> >> >> > failed
>> >> >> > > > >> >> > to
>> >> >> > > > >> >> > search related code in the
source code of drlvm).
>> >> >> > > > >> >> > If so , when ?Before or after
the jni available ?
>> >> >> > > > >> >> > Since I am trying to implement
the osgi on harmony and
>> >> >> > > > >> >> > the
>> >> osgi
>> >> >> > > > works
>> >> >> > > > >> >> with
>> >> >> > > > >> >> > bundles (modules) , I think
I need to know the
>> >> >> > > > >> >> > procedure
>> >> of
>> >> >> > booting
>> >> >> > > > >> and
>> >> >> > > > >> >> > loading of class from different
modules at the start
>> >> >> > > > >> >> > up
>> >> time.
>> >> >> > > > >> >> > Any clue about this ?Thanks
>> >> >> > > > >> >> >
>> >> >> > > > >> >> > plus,do we have the source
code of java.exe ?Where?
>> >> >
>> >> >
>> >> >
>> >>
>> >>
>> >>
>> >> --
>> >> http://people.apache.org/~xli
>> >>
>> >
>> >
>> >
>> > --
>> > Regards
>> > Michael Tian
>> >
>>
>
>
>

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