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https://issues.apache.org/jira/browse/LOG4J2-3427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17503794#comment-17503794
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ASF subversion and git services commented on LOG4J2-3427:
---------------------------------------------------------
Commit 7594b07cb7b6279469190c82ae8ef4fa2bda76ba in logging-log4j2's branch
refs/heads/release-2.x from Piotr P. Karwasz
[ https://gitbox.apache.org/repos/asf?p=logging-log4j2.git;h=7594b07 ]
[LOG4J2-3427] Add a ServiceLoader tool
This adds a `ServiceLoader` which:
* automatically discards service classes, which can not be instantiated
(e.g. classes in the server's classloader of a servlet container), from
the list of returned services,
* implements a common mechanism to override the service found by
`ServiceLoader`,
* adds warnings if we only need one service, but multiple candidates
are found.
> ServiceLoader usage in a servlet environment
> --------------------------------------------
>
> Key: LOG4J2-3427
> URL: https://issues.apache.org/jira/browse/LOG4J2-3427
> Project: Log4j 2
> Issue Type: Improvement
> Reporter: Piotr Karwasz
> Assignee: Piotr Karwasz
> Priority: Major
>
> It is fair to assume that a servlet container like Tomcat might contain
> multiple copies of Log4j 2.x:
> * a copy of Log4j 2.x can be used as logging provider for the entire server,
> * each web application can contain another copy of Log4j 2.x
> One of the shortcomings of {{ServiceLoader}} is that it detects services in
> both the web application's and server's classloader, but only those in the
> web application are usable: those in the server's classloader can not extend
> the service class contained in the application's classloader.
> A typical usage of {{ServiceLoader}} to find all instances of a certain
> service can therefore end up in a {{{}ServiceConfigurationError{}}}. Those
> are caught in Log4j 2.x, but usually end up in all services (also the viable
> ones) being {*}discarded{*}.
> Hence a tool is necessary to only discard those services, which are contained
> in the server's classloader.
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