Apache 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.
Graylog Extended Log Format (GELF) implementation in Java for all major logging frameworks: log4j, log4j2, java.util.logging, logback, JBossAS7 and WildFly 8-12
A structured logger for Fluentd (Java)
A sub microsecond java logger, supporting standard logging APIs such as Slf & Log4J