The Apache Software Foundation
Community-led development since 1999.
Apache Log4j 2.x
What is it?
Log4j 2 is an upgrade to Log4j that provides significant improvements over its predecessor, Log4j 1.x, and provides many of the improvements available in Logback while fixing some inherent problems in Logback's architecture.
With log4j it is possible to enable logging at runtime without modifying the application binary. The log4j package is designed so that these statements can remain in shipped code without incurring a heavy performance cost. Logging behavior can be controlled by editing a configuration file, without touching the application binary.
log4j 2.x home page: http://logging.apache.org/log4j/2.x/
Log4j2ReleaseGuide - The steps required to perform a Log4j 2 release.