JCL 1.2 implemented over SLF4J
Log4j implemented over SLF4J
The Apache Log4j SLF4J API binding to Log4j 2 Core
Version 99.0-does-not-exist is a dummy implementation with actually does nothing, and most of all: it has no dependencies. VERSION 99.0-does-not-exist IS NOT IN ANY WAY AFFILIATED WITH THE ORIGINAL DEVELOPERS of commons-logging NOR WITH APACHE.
The Apache Log4j Commons Logging Adapter
JBoss Logging Log4j Implementation