A simple example of log4j

This Example shows you how to create a log in a program.

Description of the code:

Logger.getLogger(): Logger class is used for handling the majority of log operations and getLogger method is used for return a logger according to the value of the parameter. If the logger already exists, then the existing instance will be returned. If the logger is not already exist, then create a new instance.
Logger.debug(): This method is used to check that the specified category is DEBUG enabled or not, if yes then it converts the massage passed as a string argument to a string by using appropriate object renderer of class ObjectRenderer.
Logger.info(): This method is used to check that the specified category is INFO enabled or not, if yes then it converts the massage passed as a string argument to a string by using appropriate object renderer of class ObjectRenderer.
Logger.warn(): This method is used to check that the specified category is WARN enabled or not, if yes then it converts the massage passed as a string argument to a string by using appropriate object renderer of class ObjectRenderer.
Logger.error(): This method is used to check that the specified category is ERROR enabled or not, if yes then it converts the massage passed as a string argument to a string by using appropriate object renderer of class ObjectRenderer.
Logger.fatal(): This method is used to check that the specified category is FATAL enabled or not, if yes then it converts the massage passed as a string argument to a string by using appropriate object renderer of class ObjectRenderer.

LogExample.java




import org.apache.log4j.Logger;



public class LogExample {



  public LogExample() {

  }

  static Logger log = Logger.getLogger(LogExample.class);



  public static void main(String argsp[]) {



  log.debug("Here is some DEBUG");

  log.info("Here is some INFO");

  log.warn("Here is some WARN");

  log.error("Here is some ERROR");

  log.fatal("Here is some FATAL");

  }

}

log4j.properties



log4j.rootLogger=debug, stdout

log4j.appender.stdout=org.apache.log4j.ConsoleAppender

log4j.appender.stdout.Target=System.out

log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

log4j.appender.stdout.layout.ConversionPattern=[%5p] %d{mm:ss} 

    (%F:%M:%L)%n%m%n%n

Output:


[DEBUG] 55:17 (LogExample.java:main:11)

Here is some DEBUG



[ INFO] 55:17 (LogExample.java:main:12)

Here is some INFO



[ WARN] 55:17 (LogExample.java:main:13)

Here is some WARN



[ERROR] 55:17 (LogExample.java:main:14)

Here is some ERROR



[FATAL] 55:17 (LogExample.java:main:15)

Here is some FATAL

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