What is Log4J. An absolute beginners tutorial.

Java Program Using log4j:

The below java code helps in understanding initialization and use of Log4j logging library. User need to create log4j2.xml file and use the same in the program.

<?xml version="1.0" encoding="UTF-8"?>
<configuration status="WARN">
 <appenders>
    <File name="MyFile" fileName=" Applicationdemo.log ">
        <PatternLayout pattern="%d{yyyy-mm-dd HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
    </File> 
 </appenders>
 <loggers> 
    <root level="debug">
        <appender-ref ref="MyFile " level="info"/>
        <appender-ref ref="MyFile" level="error"/>
    </root> 
 </loggers>
</configuration>

Sample Class

import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.LogManager;
 
public class Log4jConfigurationExample
{
  static final Logger logger_c = LogManager.getLogger(Log4jConfigurationExample.class.getName());

    public static void main(String[] args)
    {
        
 
        //log file and Log in console
        logger_c.debug("Configuration is successful Log4j appender!!");
        logger_c.info( "onfiguration is successful Log4j appender!!");
    }
} 

Compilation and Run:

Set the PATH and CLASSPATH for log4j2.xml file in the System. Save the program as Log4jConfigurationExample.java, compile and run the program. The result will be output on console and Applicationdemo.log in project folder as below.

Configuration is successful Log4j appender!!");

Configuration is successful Log4j appender!!");