Log4j ConsoleAppender Configuration Example

Any logging application intended to print logging information to a console should use this org.apache.log4j.ConsoleAppender. ConsoleAppender is a very simple class designed to write logging information to either System.out or System.err. The destination of the log messages can be configured via a property named target.

Properties of ConsoleAppender

The configurable properties of ConsoleAppender are described below:

ConsoleAppender Configuration

ConsoleAppender configuration in properties file

log4j.rootCategory=debug,console
log4j.logger.com.demo.package=debug,console
log4j.additivity.com.demo.package=false
 
log4j.appender.console=org.apache.log4j.ConsoleAppender
log4j.appender.console.target=System.out
log4j.appender.console.immediateFlush=true
log4j.appender.console.encoding=UTF-8
#log4j.appender.console.threshold=warn
 
log4j.appender.console.layout=org.apache.log4j.PatternLayout
log4j.appender.console.layout.conversionPattern=%d [%t] %-5p %c - %m%n

ConsoleAppender configuration in XML file

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration>
	<appender name="console" class="org.apache.log4j.ConsoleAppender">
		<param name="target" value="System.err"/>
		<param name="immediateFlush" value="false"/>
		<param name="encoding" value="UTF-8"/>
		<param name="threshold" value="warn"/>
		<layout class="org.apache.log4j.PatternLayout">
			<param name="conversionPattern" value="%d [%t] %-5p %c - %m%n"/>
		</layout>
	</appender>

	<logger name="com.demo.package">
		<level value="debug"/>
		<appender-ref ref="console"/>
	</logger>

	<root>
		<priority value ="debug" />
		<appender-ref ref="console"/>
	</root>
</log4j:configuration>

Test ConsoleAppender Configuration

Let’s write a quick java program and write the logs in console using above configuration.

import org.apache.log4j.Logger;
import org.apache.log4j.PropertyConfigurator;

public class Demo 
{
	static Logger logger = Logger.getLogger(Demo.class);

	public static void main(String[] args) {
		// PropertiesConfigurator is used to configure logger from properties file
		PropertyConfigurator.configure("log4j.properties");

		// Log in console
		logger.debug("Log4j console appender configuration is successful !!");
	}
}

Now put the log4j.properties file in project root folder or resources folder as per your need – and run the application. You will get below log message in console.

2016-06-14 18:03:13,175 [main] DEBUG Demo - Log4j console appender configuration is successful !!

Drop me your questions in comments section.

Happy Learning !!