[jboss-jira] [JBoss JIRA] Commented: (JBLOGGING-65) JBoss Logging fails to support log4j-over-slf4j

[David Lloyd (JIRA)]

    [ https://issues.jboss.org/browse/JBLOGGING-65?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12609745#comment-12609745 ] 

David Lloyd commented on JBLOGGING-65:
--------------------------------------

That proposed logic is unfortunately incorrect, as the StaticLoggerBinder is almost always available (lots of projects use SLF4J) but is almost never the correct choice.  It would only be the correct choice in the absence of any other log implementation, and even then it still might be the wrong choice (for example if the JBoss Logging SLF4J implementation were available, this class would be present; by your logic this would cause infinite recursion when a log message is invoked).

> JBoss Logging fails to support log4j-over-slf4j
> -----------------------------------------------
>
>                 Key: JBLOGGING-65
>                 URL: https://issues.jboss.org/browse/JBLOGGING-65
>             Project: JBoss Logging
>          Issue Type: Bug
>      Security Level: Public(Everyone can see) 
>    Affects Versions: 3.0.0.Beta5-jboss-logging
>            Reporter: Jeff Ramsdale
>            Assignee: David Lloyd
>            Priority: Critical
>
> org.jboss.logging.LoggerProviders tests for the existence of org.apache.log4j.LogManager and if it discovers it assumes Log4j is in use. This is incorrect in the scenario where log4j events are routed to slf4j for eventual routing to another logging engine (a very common use case). This engine may be Logback, but may not. Therefore, the test for whether slf4j is in use is not whether Logback is in the classpath (Logback is AN implementation of slf4j, not THE implementation...), but whether org.slf4j.impl.StaticLoggerBinder is. There should be no attempt to detect Logback itself. JBoss Logging cannot tell through simply loading org.apache.log4j.LogManager whether this class is provided by log4j or by log4j-over-slf4j so cannot use this class to detect log4j use. To clarify, the logic should be:
> 1) If org.slf4j.impl.StaticLoggerBinder is available, use slf4j.
> 2) If org.apache.log4j.LogManager (but not StaticLoggerBinder) is available, use log4j.
> 3) Otherwise use java.util.logging

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