Apache Commons Logging library.

There is a great need for debugging and logging information inside of Commons
components such as HTTPClient and DBCP. However, there are many logging APIs
out there and it is difficult to choose among them.

The Logging package is an ultra-thin bridge between different logging
libraries. Commons components may use the Logging API to remove compile-time
and run-time dependencies on any particular logging package, and contributors
may write Log implementations for the library of their choice.

WWW: http://commons.apache.org/proper/commons-logging/