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From "Stephan Siano (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ARIES-1108) Discuss a better user experience when dealing with service dependencies.
Date Thu, 29 Aug 2013 06:44:52 GMT

    [ https://issues.apache.org/jira/browse/ARIES-1108?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13753372#comment-13753372
] 

Stephan Siano commented on ARIES-1108:
--------------------------------------

I like the idea (5) because the subsystem implementation kind of provides the root subsystem
and the services exported by these bundles are somewhat provided by the root subsystem.

Option 4 might also help in several cases, however not all services are provided by DS or
blueprint (although this is good practice).

Option 1 is a long term solution, however I don't know how long it takes till everybody has
taken this up (even if it becomes a best practice).

Updating the maven-bundle-plugin probably won't help much. The Export-Service header is generated
for blueprint bundles (and those do already work).

The import and export service headers are somehow informational only, and I don't think that
changing the semantics of that is a good idea.

What does uninstalling the application modeller mean, are only service requirements not computed
or also wiring stuff (pakage imports etc.)?
                
> Discuss a better user experience when dealing with service dependencies.
> ------------------------------------------------------------------------
>
>                 Key: ARIES-1108
>                 URL: https://issues.apache.org/jira/browse/ARIES-1108
>             Project: Aries
>          Issue Type: Brainstorming
>          Components: Subsystem
>            Reporter: John Ross
>
> Currently, Aries Subsystems will compute service requirements and capabilities for Blueprint
bundles only. This can be particularly problematic for users with application subsystems having
bundles with service dependencies on non-blueprint bundles outside of their control. For example,
an application blueprint bundle with a service dependency on EventAdmin will fail to resolve
unless the EventAdmin implementation bundle advertises the service capability in some supported
way. To get around this, the user must either (1) turn the bundle into a blueprint bundle,
(2) add a Provide-Capability header to the bundle's manifest, or (3) provide their own bundle
with a Provide-Capability header advertising all of the services of interest.
> The following represents a non-exhaustive list of possibilities.
> (1) Engage bundle providers to include a Provide-Capability header advertising services.
This would be particularly helpful for standard OSGi services. Engage OSGi to make this a
requirement or best practice.
> (2) Update the maven bundle plugin to generate this header, as it currently does for
the Export-Service header.
> (3) Support Import-Service and Export-Service headers in Aries Subsystems. These headers
are already generated by the maven bundle plugin.
> (4) Support DS in Aries Subsystems.
> (5) Add some sort of service listener to Aries Subsystems that will ensure existing services
are available as "virtual capabilities" to resolving subsystems.
> Note that in Aries Subsystems 1.0.1-SNAPSHOT+, the ModelledResourceManager service, used
to compute service requirements and capabilities, is now optional. This means users can uninstall
(or not install) the org.apache.aries.application.modeller bundle in order to disable service
resolution.

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