[jira] [Commented] (SLING-5041) Clarify the order of the iterator given by RankedServices

["Konrad Windszus (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SLING-5041?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15070964#comment-15070964 ] 

Konrad Windszus commented on SLING-5041:
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This is my proposal on how to fix this:
# Deprecate {{ServiceUtil.getComparableForServiceRankings()}} and instead add two methods {{ServiceUtil.getComparableForServiceRankingsHighestFirst()}} and {{ServiceUtil.getComparableForServiceRankingsLowestFirst()}}. The latter is also called by the deprecated method {{ServiceUtil.getComparableForServiceRankings()}}.
The javadoc of both methods should clarify, when to use which comparable. The former is useful for implementing an order similar to what is used by {{BundleContext.getServiceReference()}}, i.e. highest rank first. I am not quite sure for what purpose you would need the latter though but we need it to be backwards-compatible (lowest rank first).
# For {{RankedServices}} itself I would rather go for incrementing the package version to 3.0 and just fix the iterator order from ascending to descending (i.e. highest first) by internally relying on the new {{ServiceUtil.getComparableForServiceRankingsHighestFirst()}}. The way it is implemented right now is really not that useful and rather contradicts OSGi rules.

The alternative would be to deprecate {{RankedServices}} and introduce a new interface {{OSGiCompliantRankedServices}} which inverts the order.

[~sseifert@pro-vision.de][~cziegeler][[~bdelacretaz] WDYT? Which way would you prefer?

> Clarify the order of the iterator given by RankedServices
> ---------------------------------------------------------
>
>                 Key: SLING-5041
>                 URL: https://issues.apache.org/jira/browse/SLING-5041
>             Project: Sling
>          Issue Type: Improvement
>          Components: Commons
>    Affects Versions: Commons OSGi 2.3.0
>            Reporter: Konrad Windszus
>
> Currently the iterator in {{RankedServices}} returns the services in the ascending order from lowest to highest ranking. This is a different order then being used by OSGi internally [1]. Usually you are only interested in an iterator which gives you the service with the highest ranking first (because that would also be the one being returned by {{BundleContext.getServiceReference(...)}}).
> If we don't change the iterator logic we should at least make it clearer in the Javadoc that the iterator really gives the services in ascending order of their service ranking property and we should probably add a more useful iterator which gives back the services with the highest ranking first.
> The issue came up in the context of SLING-5035.
> [1] - https://osgi.org/javadoc/r4v42/org/osgi/framework/BundleContext.html#getServiceReference(java.lang.String)



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