Log4j Appenders

previous next TOC

Log4j appenders

Output targets are implemented by appenders. Appenders exists for java.io.Writer, the console, files, Unix syslog, JMS, NT Event log, SMTP, and more.
Multiple appenders can be attached to any logger.
Appenders follow the logger hierarchy in an additive fashion.

All existing appenders are derived from AppenderSkeleton class which implements the Appender interface.

It is possible to log asynchronously.

Use the Logger.addAppender method to attach an appender to a logger.

Appender Additivity
The output of a log statement of logger L will go to all the appenders in L and its ancestors. This is the meaning of the term "appender additivity".
However, if an ancestor of logger L, say P, has the additivity flag set to false, then L's output will be directed to all the appenders in L and it's ancestors up to and including P but not the appenders in any of the ancestors of P.
Loggers have their additivity flag set to true by default.

GET THE DOCS DIRECTLY FROM THE DEVELOPER

For up to date and detailed log4j documentation directly from the developer please consider The complete log4j manual.