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Re: [equinox-dev] Resolver Problem with guava and e4 (javax.annotation)

Importing what you export is only useful when the bundle contains other packages which actually use the exported package. For example, a bundle implements the OSGi Event Admin service. That bundle can export the org.osgi.service.event package and also import it. The bundle is happy to use any (version matching) org.osgi.service.event package.

But if the bundle is just a "container" of packages which it exports for other and does not itself use the packages in anyway, then there is less value in also importing the packages. Say a bundle just contains the org.osgi.service.event package and exports it as well as imports it. If this bundle is resolved to import the package, the bundle is essentially empty. It is not exporting the package and has no other packages.

I don't know the make up of the bundles in question here. But is may or may not make sense to import the packages being exported. What the bundle contains will influence the choice. That being said, there is little harm in also importing the packages, so it is a safe (but perhaps of little value) choice.

BJ Hargrave
Senior Technical Staff Member, IBM
OSGi Fellow and CTO of the
OSGi Alliance

office: +1 386 848 1781
mobile: +1 386 848 3788

From:        Andreas Sewe <andreas.sewe@xxxxxxxxxxxxxx>
To:        equinox-dev@xxxxxxxxxxx, orbit-dev@xxxxxxxxxxx
Date:        2014/07/11 04:38
Subject:        Re: [equinox-dev] Resolver Problem with guava and e4        (javax.annotation)
Sent by:        equinox-dev-bounces@xxxxxxxxxxx

David M Williams wrote:
> I notice in Orbit, all our "javax.annotation" bundles follow the import
> what you export pattern .... that's good, such as
> *Export-Package*: javax.annotation;/version/="1.2.0",
>  javax.annotation.security;/version/="1.2.0",
>  javax.annotation.sql;/version/="1.2.0"
> *Import-Package*: javax.annotation;/version/="1.2.0",
>  javax.annotation.security;/version/="1.2.0",
>  javax.annotation.sql;/version/="1.2.0"

Is this "import what you export" best practice for *all* javax.* bundles
in Orbit? As far as I can see, some of them don't follow this policy
(javax.xml.bind, for example, whose packages are also provided by the
system bundle provides at least from Java 7 onwards) and I am wondering
whether it's worth opening bugs for this.

Best wishes,


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