Packages 
Package Description
org.apache.commons.logging
Jakarta Commons Logging implemented over SLF4J.
org.apache.commons.logging.impl
SLF4J based implementation of commons-logging wrapper APIs.
org.apache.log4j
An rather minimal but sufficient implementation redirecting all calls to a log4j logger to a logback logger.
org.apache.log4j.helpers  
org.apache.log4j.spi  
org.apache.log4j.xml  
org.slf4j
Core logging interfaces.
org.slf4j.bridge
Bridge/route all JUL log records to the SLF4J API.
org.slf4j.event  
org.slf4j.helpers
Helper classes.
org.slf4j.impl
Implementations of core logging interfaces defined in the org.slf4j package.
org.slf4j.spi
Classes and interfaces which are internal to SLF4J.