Log4j2 : Console Appender: Writes output to system console

Appenders are responsible for delivering log messages to external world like files, database, console, socket etc., You can attach filters to appenders to filter the log messages, and formatters to format the log messages before sending them to destination.

Console appender writes log messages to either System.out (or) System.err.

Following are the parameters for Console appender.

Parameter	Type	Description
filter	Filter	Filters are used to filter the log events. Filters take the decision, whether to  log the event (or) not.
layout	Layout	Layout is used to format the log event. By default ‘"%m%n" ‘ pattern layout is used.
follow	boolean	Identifies whether the appender honors reassignments of System.out or System.err via System.setOut or System.setErr made after configuration.
name	String	Name of the appender
ignoreExceptions	boolean	If it set to false, then exceptions will be propagated to the caller. Default value is true.
target	String	Either "SYSTEM_OUT" or "SYSTEM_ERR", default is "SYSTEM_ERR".

log4j2.xml

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="DEBUG" monitorInterval="30">
 <Appenders>
  <Console name="my_console_appender" target="SYSTEM_OUT">
   <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
  </Console>
 </Appenders>
 <Loggers>
  <Root level="info">
   <AppenderRef ref="my_console_appender" />
  </Root>
 </Loggers>
</Configuration>

package log4j_tutorial;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class HelloWorld {
 private static final Logger logger = LogManager.getLogger();

 public static void main(String args[]) {
  logger.trace("Trace Message!");
  logger.debug("Debug Message!");
  logger.info("Info Message!");
  logger.warn("Warn Message!");
  logger.error("Error Message!");
  logger.fatal("Fatal Message!");
 }
}

You can see following messages in console.

19:06:20.828 [main] INFO  log4j_tutorial.HelloWorld - Info Message!

19:06:20.828 [main] WARN  log4j_tutorial.HelloWorld - Warn Message!

19:06:20.828 [main] ERROR log4j_tutorial.HelloWorld - Error Message!
19:06:20.828 [main] FATAL log4j_tutorial.HelloWorld - Fatal Message!

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