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https://issues.apache.org/jira/browse/LOG4J2-3427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17508600#comment-17508600
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Piotr Karwasz commented on LOG4J2-3427:
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Actually I think there are at the moment two problems in the way, e.g.
{{PropertiesUtil}} work in a servlet environment. Assuming there is a copy of
{{log4j-api}} in both the web application and the server classloaders:
# the copy in the web application's classloader will fail to detect *any*
property source: it will find the classes in the parent classloader and throw
an exception, because they don't extend {{{}PropertySource{}}}.
# the copy in the server's classloader (which can be reached if the webapp
does not have {{{}log4j-api{}}}) will use the context classloader to find
property sources in the webapp classloader and binding them to a static field.
This causes a memory leak.
> 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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