I was facing the same problem. Glassfish default logging is ugly and unreadable for my taste, and the rest of my project uses SLF4J (with logback as backend, but my approach would also work for the log4j backend).
The details are described here:
http://hwellmann.blogspot.com/2010/05/glassfish-logging-with-slf4j.html
With this setup, you should not even see the multiple bindings warnings, except when using Embedded Glassfish, where you don't have OSGi to encapsulate the different bindings.
Of course, all of this is rather a mess and I'd really prefer Glassfish to offer a pluggable logging API, like SLF4J.
Hope that helps,
Harald
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