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Re: [equinox-dev] Re: boot class path extension bundles in Eclipse/Equinox



> Jay,
>
> Technically, any file can be deployed via a feature/bundle. The only real
> issue is how one gets the jar into the xbootclasspath at startup.  


The OSGi R4 specification does define a way to do this with what is called
boot classpath extension bundles.  These bundles act as fragments to the
system.bundle and they can specify additional libraries that can be
appended to the boot classpath.

> As you
> know, the IBM WMC version of the RCP uses a configuration file to configure
> the launch environment and that can be modified via feature installhandler
> to add a jar contained in some bundle to the boot classpath, thus meaning
> any file, including boot path jars, can be updated.
>


This sound very similar to the <launcher>.ini file that is supplied with
eclipse to configure the eclipse launcher.  The problem I see with this
approach is the use of install handlers that must be intimately aware of the
framework.  For example, how does it know what order to put the jars on the
boot classpath.  The boot classpath extensions spec in OSGi R4 handles these
details for you.

> I guess you are really asking if Equinox/Eclipse should be providing some
> similar capability for 'standard' eclipse.  Is that correct?  In that case,
> that's a fair thing to ask.
>
> This topic sort of crosses over into the dev-update list, because it covers
> update, but since this is also 'new ground' for platform lifecycle, it does
> probably need to be vetted here as well.

Yup, I opened bug https://bugs.eclipse.org/bugs/show_bug.cgi?id=127724
to consider implementing boot classpath extensions.

> One of the key aspects that enables the 'updating of everything' in the WMC
> architecture is to use a two-stage launch.  The first launcher process,
> which terminates as a process after it is done, includes code to finish and
> clean up install/update steps that affect the launch of the runtime
> process.  The main task of the first launch phase is to configure the
> launch environment for the runtime process.  Because the first launcher is
> not running during the runtime, it can itself be changed during an update.
>
> Is it time to start talking about incorporating any of these ideas into
> eclipse?
>
> [Side note - Andrew Davis will be doing a short 'lightening talk' on
> 'updating the entire world' at EclipseCon.  I can't be there, but Andrew
> will go over some of the techniques that we use to make it possible to
> update every single aspect of the system.]
>
> -mel
>