log4j Tutorial - Log4j Logging Methods

Logger class has methods to handle logging activities. We can create instance of the Logger class with two static methods:

public static Logger getRootLogger();
public static Logger getLogger(String name);

The first method returns the root logger without a name. The second method returns a logger by name. The name of the logger can be any string. We normally use the class or package name as follows:

static Logger log = Logger.getLogger(log4jExample.class.getName());

Logging Methods

We can use the following methods from the Logger class to log messages.

Methods	Description
public void debug(Object message)	prints messages with the level Level.DEBUG.
public void error(Object message)	prints messages with the level Level.ERROR.
public void fatal(Object message)	prints messages with the level Level.FATAL.
public void info(Object message)	prints messages with the level Level.INFO.
public void warn(Object message)	prints messages with the level Level.WARN.
public void trace(Object message)	prints messages with the level Level.TRACE

All the levels are defined in the org.apache.log4j.Level class.

import org.apache.log4j.Logger;

public class Main {
   private static org.apache.log4j.Logger log = Logger.getLogger(Main.class);
   public static void main(String[] args) {
      log.trace("Trace Message!");
      log.debug("Debug Message!");
      log.info("Info Message!");
      log.warn("Warn Message!");
      log.error("Error Message!");
      log.fatal("Fatal Message!");
   }
}