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From "Stuart McCulloch" <stuart.mccull...@jayway.net>
Subject Re: Support for OSGi
Date Thu, 31 Jan 2008 15:52:42 GMT
On 31/01/2008, Oberhuber, Martin <Martin.Oberhuber@windriver.com> wrote:
>
> Hello Niall,
>
> it would be interesting for Eclipse consumers as
> well to get Apache bundles with Meta-info already
> applied.
>
> Currently, the Meta-info is mostly added manually
> as part of the Eclipse Orbit project.
>
> I have had a brief look at your auto-generated
> MANIFEST for commons net, and found a few issues:
>
> http://people.apache.org/~niallp/commons-osgi/commons-net-1.5.0-SNAPSHOT
> -MANIFEST.MF
>
> 1. Import-Package: examples;version="1.5.0.SNAPSHOT"
>    this is just wrong. The commons net deliverable
>    jar should not import examples.


I assume there's an examples package somewhere (or something pulls in the
examples package)
You can explicitly ask Bnd to remove/ignore this import by using !examples
in the Import-Package
if you know that you won't actually need it during runtime (ie. it's
dead/unused code)

eg:   <Import-Package>!examples,*</Import-Package>

2. Import-Package: org.apache.commons.net.smtp
>    this is also wrong though less destructive.
>    commons.net.smtp is really exported and not imported.


Actually this is correct - it's good practice to import your exports as it
ensures a consistent class
space and avoids problems when upgrading bundles. Otherwise you *will* run
into casting issues.

3. Export-Package:
> org.apache.commons.net.smtp;uses:="org.apache.commons.net.io,org.apache.
> commons.net"
>    It's useless to add a "uses" directive for
>    packages that are in the same bundle. At
>    Eclipse-Orbit, we've found problems with "uses"
>    and decided to no longer use it.


As Peter says, he's recently updated Bnd to give users more control over
"uses" and improved
the default generation. BTW, there is a good reason for the "uses" clause as
explained by Glyn:


http://underlap.blogspot.com/2007/10/osgi-type-safety-and-uses-directive.html

I haven't seen any problem with "uses" on Felix, but I guess Equinox could
always add an option
to ignore it - as there are likely to be other bundles out there that have
"uses" in their manifest.

I guess that these should perhaps really be bug
> reports against the Bnd utility which autogenerated
> the Manifest; Tool: Bnd-0.0.227.


The elimination of "uses" is really a new feature, and the imports of
exports is not a bug - the
only bug (as such) is the appearance of the "examples" package, but I'd need
to see the final
jar to understand why Bnd detected it (ie. it may be a justified import
based on the content)

But for me, it also shows that in the current stage
> it looks like the OSGi manifest still needs to be
> written by hand and not auto-generated.


>From experience I'd argue it's the other way round - OSGi manifests should
be auto-generated.
But, as with any tool, you should verify it yourself and add any customized
attributes and minor
adjustments.

Otherwise you'll have to manually keep the manifest in step with your code,
and it's amazingly
easy to miss imports when they're buried inside the code, which is why such
tools are needed.

The other benefit of auto-generation is you can do it dynamically - for
example, at OPS4J we
have a deployment tool that lets you load third-party jars which
automatically get turned into
OSGi bundles. This really helps with rapid prototyping (great if you have a
legacy jar, but don't
know the code well enough to craft an OSGi manifest yourself)

Anyways, if there is a plan to make a downloadable
> release of any commons packages with OSGi info
> added, I'd like to know.
>
> Thanks,
> --
> Martin Oberhuber, Senior Member of Technical Staff, Wind River
> Target Management Project Lead, DSDP PMC Member
> http://www.eclipse.org/dsdp/tm
>
>
>
> > -----Original Message-----
> > From: Niall Pemberton [mailto:niall.pemberton@gmail.com]
> > Sent: Tuesday, January 29, 2008 11:30 PM
> > To: Commons Developers List
> > Cc: dev@felix.apache.org
> > Subject: Re: Support for OSGi
> >
> > I have created a JIRA ticket for the changes to the commons-parent pom
> > to add the bundle plugin:
> >   https://issues.apache.org/jira/browse/COMMONSSITE-23
> >
> > I have also tested out the plugin by generating the jars/manifest for
> > all but three components:
> >   http://people.apache.org/~niallp/commons-osgi/
> >
> > I'll leave the ticket open for a few days - but unless there are
> > objections/issues raised I plan to apply the changes to
> > commons-parent.
> >
> > Niall
> >
> > On Dec 19, 2007 2:38 PM, Carsten Ziegeler
> > <cziegeler@apache.org> wrote:
> > > Hi,
> > >
> > > the products of commons are highly used throughout many projects.
> > >
> > > It would be great, if the projects here at Apche Commons could help
> > > those projects that are using OSGi.
> > >
> > > OSGi is based around the concept of a bundle - a bundle is
> > a jar file
> > > with additional meta data like the packages it exports and a list of
> > > external packages it is using (please forgive me if I'm
> > simplifying here
> > > too much).
> > >
> > > As many projects are using artifacts from Apache Commons,
> > they need the
> > > specific jars as bundles. This is most often done by
> > creating so called
> > > wrapper bundles: these are jars that have the same contents as the
> > > original library with the addition of the required meta data.
> > > You can find several examples here:
> > >
> > > http://svn.apache.org/repos/asf/felix/trunk/commons/
> > >
> > > Now, it would be great, if the projects here at Apache Commons would
> > > already provide artifacs that can be directly used in an
> > OSGi environment.
> > >
> > > All that has to be done is adding some entries to the
> > manifest. This is
> > > usually a list of imported packages, a list of exported packages, a
> > > symbolic name for the bundle and a version. (There are some more but
> > > these are the most important ones).
> > >
> > > Adding these entries can be done by hand (not recommended)
> > or with tools
> > > automatically. For example the Apache Felix maven
> > bundleplugin requires
> > > just some lines of configuration and that's it.
> > >
> > > It would be great if some of the projects here could add
> > these meta data
> > > as part of their next release. This will make the life of
> > all projects
> > > using OSGi much much easier.
> > >
> > > So if you're interested in helping us, just let us know. We would be
> > > happy to make the required changes to the poms or whatever
> > needs to be
> > > done. I cc'ed the Felix dev list as some Felix developers
> > might not be
> > > subscribed to the commons dev list, so please keep them
> > cross posted.
> > >
> > > Thanks
> > > Carsten
> > > --
> > > Carsten Ziegeler
> > > cziegeler@apache.org
> > >
> > >
> > ---------------------------------------------------------------------
> > > To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org
> > > For additional commands, e-mail: dev-help@commons.apache.org
> > >
> > >
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org
> > For additional commands, e-mail: dev-help@commons.apache.org
> >
> >
>



-- 
Cheers, Stuart

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