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https://issues.apache.org/jira/browse/LOG4J2-2853?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Matt Sicker resolved LOG4J2-2853.
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Fix Version/s: 3.0.0
Resolution: Fixed
Merged in master.
> Add plugin/bean qualifiers to unify instance selection for dependency
> injection
> -------------------------------------------------------------------------------
>
> Key: LOG4J2-2853
> URL: https://issues.apache.org/jira/browse/LOG4J2-2853
> Project: Log4j 2
> Issue Type: New Feature
> Components: Core
> Reporter: Matt Sicker
> Assignee: Matt Sicker
> Priority: Major
> Fix For: 3.0.0
>
>
> In the 2.x plugin API, we have numerous ways of specifying metadata to a
> variable or performing manual configuration tree traversal in order to
> resolve the value of that variable from the user configuration. These include
> most of the {{@Plugin}} annotations as well as some system properties.
> In the 3.0 API, we should unify this into a "qualifier" concept. A
> plugin/bean can contain one or more qualifiers which are specified by
> annotations and matched at runtime to the injection target qualifiers.
> Qualifiers are inspired by the [corresponding concept in
> javax.inject|https://docs.oracle.com/javaee/6/api/javax/inject/Inject.html],
> though they shouldn't be limited to only one qualifier on an injection target
> or plugin/bean. Like in CDI, multiple qualifiers should be allowed to be
> specified.
> Within a scope (LOG4J2-2852), plugins/beans will have at most one instance
> per unique set of qualifiers. Qualifiers will typically be placed on plugin
> classes or on injection targets, while configuration trees will emit
> specially qualified plugins/beans for injection into Core plugins which take
> injected parameters. Existing plugin annotations should be updated to work as
> corresponding qualifiers without requiring code updates on the plugin side
> (even though this will allow us to simplify and clean up various parts of our
> own code base over time).
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