Log4j example in java using properties file

• Logging is very important part of programming. Logging helps programmer to understand process flow and identify the problems where actually occurred.
• Log4J will be configured externally using properties file. We can print the logging statements in the console or we can push them in to a log file based on the requirement.
•  org.apache.log4j class will provide required classes to implement logging
• We need to add Log4J dependency in our project.
• Create instance of logger by using Logger.getLogger(Log4JExample.class);
• Lets see how to create log4j.properties file in eclipse

1. Create a maven project and add Log4J dependency:

2. Create log4j.properties file

1. log4j.rootLogger=INFO, console
2. 
   
3. log4j.appender.console=org.apache.log4j.ConsoleAppender
4. 
   
5. log4j.appender.console.layout=org.apache.log4j.PatternLayout
6. log4j.appender.console.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss.SSS zzz}

3.Create java example program to read log4j.properties file

1. import org.apache.log4j.BasicConfigurator;
2. import org.apache.log4j.Logger;
3. 
   
4. public class Log4JExample {
5. 
   
6. static Logger logger = Logger.getLogger(Log4JExample.class);
7.     public static void main(String[] args)
8.     {
9.     BasicConfigurator.configure();
10.     logger.info("main method start!!");
11.    
12.     System.out.println("hi");
13.     logger.info("log4j properties configuration example");
14.      
15.     logger.info("main method end!!");
16.     }
17. }

Output:

1. 2018-02-08 23:09:10.747 IST0 [main] INFO Log4JExample  - main method start!!
2. hi
3. 2018-02-08 23:09:10.752 IST5 [main] INFO Log4JExample  - log4j properties configuration example
4. 2018-02-08 23:09:10.753 IST6 [main] INFO Log4JExample  - main method end!!