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https://issues.apache.org/jira/browse/SLING-2575?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Alexander Klimetschek updated SLING-2575:
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Description:
Managing a SCR @Reference that's basically a list is very difficult when
compared to the simple unary, static reference. It seems a typical use case is
0..n cardinality, dynamic policy and ordered by service ranking with the higher
ranked ones first. This supports the use case to ask a list of services and
have the first responding one win.
There is the ServiceTracker [0], but its getServiceReferences() method does not
return the list sorted in any way, only gives your references and not the typed
object(s) and it's a bit cumbersome to use.
A typical manual approach can be seen in the SlingPostServlet [1] in the
register*() methods. Important is to handle thread-safeness.
[0] http://www.osgi.org/javadoc/r4v42/org/osgi/util/tracker/ServiceTracker.html
[1]
http://svn.apache.org/repos/asf/sling/trunk/bundles/servlets/post/src/main/java/org/apache/sling/servlets/post/impl/SlingPostServlet.java
was:
Managing a SCR @Reference that's basically a list is very difficult when
compared to the simple unary, static reference. It seems a typical use case is
0..n cardinality, dynamic policy and ordered by service ranking with the higher
ranked ones first. This supports the use case to ask a list of services and
have the first responding one win.
There is the
[ServiceTracker|http://www.osgi.org/javadoc/r4v42/org/osgi/util/tracker/ServiceTracker.html],
but its getServiceReferences() method does not return the list sorted in any
way, only gives your references and not the typed object(s) and it's a bit
cumbersome to use.
A typical manual approach can be seen in the
[SlingPostServlet|http://svn.apache.org/repos/asf/sling/trunk/bundles/servlets/post/src/main/java/org/apache/sling/servlets/post/impl/SlingPostServlet.java]
in the register*() methods. Important is to handle thread-safeness.
Summary: Utility for tracking a multi-cardinality OSGi service
reference (was: Helper for tracking a multi-cardinality OSGi service reference)
> Utility for tracking a multi-cardinality OSGi service reference
> ---------------------------------------------------------------
>
> Key: SLING-2575
> URL: https://issues.apache.org/jira/browse/SLING-2575
> Project: Sling
> Issue Type: Improvement
> Components: Commons
> Reporter: Alexander Klimetschek
> Priority: Minor
>
> Managing a SCR @Reference that's basically a list is very difficult when
> compared to the simple unary, static reference. It seems a typical use case
> is 0..n cardinality, dynamic policy and ordered by service ranking with the
> higher ranked ones first. This supports the use case to ask a list of
> services and have the first responding one win.
> There is the ServiceTracker [0], but its getServiceReferences() method does
> not return the list sorted in any way, only gives your references and not the
> typed object(s) and it's a bit cumbersome to use.
> A typical manual approach can be seen in the SlingPostServlet [1] in the
> register*() methods. Important is to handle thread-safeness.
> [0]
> http://www.osgi.org/javadoc/r4v42/org/osgi/util/tracker/ServiceTracker.html
> [1]
> http://svn.apache.org/repos/asf/sling/trunk/bundles/servlets/post/src/main/java/org/apache/sling/servlets/post/impl/SlingPostServlet.java
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