That logging setup is invalid.
For slf4j, you have 3 categories of dependencies to worry about.
1) the slf4j-api.jar (required always)
2) the logging library you want to use to write logs to disk or screen.
choose 1 and only 1 (this is not a technical requirement of slf4j, but it makes managing things easier)
this list includes the following artifacts:
* slf4j-simple.jar (the provider of org.slf4j.impl.SimpleLogger)
* slf4j-jcl.jar (slf4j to jakararta commons-logging)
* slf4j-jdk14.jar (slf4j to java.util.logging)
* slf4j-log4j12.jar (slf4j to log4j)
* logback-classic.jar (slf4j to logback)
lets say you want to use log4j to manage the "to disk" portion.
that means you'll have the log4j.jar (the actual implementation) and the slf4j-log4j12.jar (the bridge from slf4j to log4j)
3) the other logging libraries you want to route to slf4j.
this list includes the following artifacts.
* jcl-over-slf4j.jar (jakarta commons logging to slf4j)
* jul-to-slf4j.jar (java.util.logging to slf4j)
* log4j-over-slf4j.jar (log4j to slf4j)
be sure you choose all of them except the library you chose in step #2
so in our case, we avoid using log4j-over-slf4j.jar (as this would cause 2 copies of the log4j classes to be present in the classpath)
For your setup you have a mystery artifact org.apache.logging.log4j:log4j-slf4j-impl:${log4j.version} no idea what that one does. I can assume from the description of the artifact that it probably does what step #2 does above, replacing slf4j-log4j12.jar (but i don't know for sure)
As for your debug statement ... [DEBUG] Logging to org.slf4j.impl.SimpleLogger(org.eclipse.jetty.util.log) via org.eclipse.jetty.util.log.Slf4jLog
... that means you have slf4j-simple.jar in your classpath. Remove that artifact from your classpath.
Also note, there's no such thing as "log4j2's simplelogger". all slf4j implementations provide a org.slf4j.impl.StaticLoggerBinder that specifies the implementation to use. If you have more than 1 instance of that specific class in your classpath then you have 2 implementations of slf4j present.
