Log4j

log4j is a framework for logging application messages written in Java. Over the years, it has become a de facto standard in the Java community with many open source and commercial software products using it.

At runtime and without recompilation, the logging level can be toggled to enable additional messages for troubleshooting. Loggers define the logging priority level and redirect the message to one or multiple Appenders. Appenders define the output channel, for example, Console, File, DailyRollingFile, Email, Socket, Telnet, JDBC, and JMS. Layout defines the output formatting, for example, SimpleLayout, PatternLayout, HTMLLayout, and XMLLayout. The Log4j configuration is done either programmatically in the Java source code, with a property file or with an XML file.