[jira] [Commented] (LOG4J2-3427) ServiceLoader usage in a servlet environment

["Nicholas Sushkin (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LOG4J2-3427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17625345#comment-17625345 ] 

Nicholas Sushkin commented on LOG4J2-3427:
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It looks like these changes break Servlet 2.5 style initialization under Tomcat 8. Could you take a look at LOG4J2-3624 ? Thanks

> 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
>             Fix For: 2.18.0
>
>
> 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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