[
https://issues.apache.org/jira/browse/SLING-5035?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14803164#comment-14803164
]
Felix Meschberger commented on SLING-5035:
------------------------------------------
Quoting the OSGi Core Specification R6 :
{panel}
*5.2.6 Service Ranking Order*
When registering a service object, a bundle may optionally specify a
SERVICE_RANKING service property of type Integer. This number specifies a
ranking order between services. The highest num- ber has the highest ranking
and the lowest number (including negative numbers) has the lowest ranking. If
no service.ranking service property is specified or its type is not Integer
then a ranking of 0 must be used.
The ranking order is defined as follows:
* Sorted on descending ranking number (highest first)
* If the ranking numbers are equal, sorted on ascending service.id property
(oldest first).
This ordering is complete because service ids are never reused and handed out
in order of their reg- istration time. That is, a service that is registered
later will have a higher service id. Therefore, the ranking order is in
descending service.ranking numeric order where ties give a preference to the
ear- lier registrant.
The ranking order is the reverse of the natural ordering of a ServiceReference
object. The purpose of the ranking order is to allow:
* Selection - When a single service must be chosen but multiple services
qualify then the service with the highest ranking must be selected.
* Ordering - When multiple services must be used in a specified order.
{panel}
So essentially the ranking is from high value to low value, the service
reference order as per {{compareTo}} is from low value to high value.
What you want here is the ranking order, that is checking the services with the
higher ranking before the services with lower values.
I think the implementation is wrong and needs to be fixed. At the same time, I
suggest to negate the service.ranking values for the default injectors and
third to update the documentation.
Yes, that might give unexpected results for current implementations which
expect the wrong behaviour -- if such implementations exist I would actually
expect them to have stumbled upon this wrong behaviour and have broken
service.ranking values to work around it.
> Sling Models Injectors should be queried in the reverse order of their
> service ranking value
> --------------------------------------------------------------------------------------------
>
> Key: SLING-5035
> URL: https://issues.apache.org/jira/browse/SLING-5035
> Project: Sling
> Issue Type: Bug
> Components: Extensions
> Affects Versions: Sling Models Impl 1.2.2
> Reporter: Radu Cotescu
> Fix For: Sling Models Impl 1.2.4
>
>
> The current version of the {{ModelAdaptorFactory}} \[0\] queries the
> Injectors in the ascending order of their service ranking value. However they
> should be queried in the descending order of the service ranking, to use the
> same logic as the {{BundleContext#getServiceReference(String)}} method \[1\].
> \[0\] -
> https://github.com/apache/sling/blob/f56b444b765beb1c31eed01b4c09fbda4013a580/bundles/extensions/models/impl/src/main/java/org/apache/sling/models/impl/ModelAdapterFactory.java#L411
> \[1\] -
> https://osgi.org/javadoc/r4v42/org/osgi/framework/BundleContext.html#getServiceReference(java.lang.String)
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
