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https://issues.apache.org/jira/browse/LOG4J2-555?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13925106#comment-13925106
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Remko Popma commented on LOG4J2-555:
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I completely agree that if there is any performance impact at all, we should
not do this.
Also, to clarify, I really don't want to over-complicate things. The idea I
mentioned in an earlier comment of having a set of FQCNs was just a thought
experiment and I now think that the benefit for custom loggers is not worth any
added complexity. Custom loggers are a rare case and simply documenting "custom
loggers must use the abstract {{log(Marker, String, Level, Message,
Throwable)}} method because they must specify _their own_ FQCN" is probably
sufficient.
The attached patch reduces complexity a little bit in many places (7 x 14
methods) and adds complexity in one place (the enums and the {{doLog}} method).
I'd like feedback on whether other people think this is a good trade-off.
Perhaps this is just a matter of taste? Anyway, feedback welcome.
I'll do some performance testing and post the results.
> Location-based functionality broken in AbstractLoggerWrapper subclasses
> -----------------------------------------------------------------------
>
> Key: LOG4J2-555
> URL: https://issues.apache.org/jira/browse/LOG4J2-555
> Project: Log4j 2
> Issue Type: Bug
> Components: API, Core
> Affects Versions: 2.0-rc1
> Reporter: Remko Popma
> Assignee: Remko Popma
> Fix For: 2.0-rc2
>
> Attachments: LOG4J2-555-delegate.patch
>
>
> *How to reproduce*
> * Create a custom logger that extends {{AbstractLoggerWrapper}} (or generate
> one with the tool attached to LOG4J2-519)
> * In the custom logger provide a public method that invokes the {{log(Level,
> String)}} method
> * Configure a pattern layout that uses location, like %C for the logger FQCN
> * From a sample app, call the public method on your custom logger.
> * The output will show the class name of the custom logger instead of the
> class name of the calling class in the sample application.
> *Cause*
> {{AbstractLogger}}'s FQCN field is {{static final}} and initialized to
> {{AbstractLogger.class.getName()}}. Then, in
> {{Log4jLogEvent#calcLocation()}}, when walking over the stack trace elements,
> the element _following_ the FQCN is returned. So only loggers that directly
> subclass from {{AbstractLogger}} will work correctly. Loggers that inherit
> from {{AbstractLoggerWrapper}} are two levels removed from {{AbstractLogger}}
> and the {{calcLocation()}} method will not work correctly.
> *Solution*
> I think {{AbstractLogger}}'s FQCN field should be made non-static, and
> initialized to {{getClass().getName()}} in the constructor of
> {{AbstractLogger}}. {{Log4jLogEvent#calcLocation()}} can then be modified to
> return the {{StackElement}} whose class name matches the FQCN, instead of the
> next element. Location-based functionality should then work for arbitrarily
> deep subclass hierarchies of AbstractLogger.
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