Apache commons logging is a kind of wrapper for other logging frameworks. If you've initialized Log4j logging in your application, Apache commons logging will sense it and use Log4J as the logging implementation.
The Logging package is an ultra-thin bridge between different logging implementations. A library that uses the commons-logging API can be used with any logging implementation at runtime. Commons-logging comes with support for a number of popular logging implementations, and writing adapters for others is a reasonably simple task.
[ October 05, 2006: Message edited by: Merrill Higginson ]