Log4J

Main steps

1. If necessary, review presentation: Log4J

2. Add dependency on log4j in pom.xml file:

       <dependencies>
       ...
           <dependency>
               <groupId>org.apache.logging.log4j</groupId>
               <artifactId>log4j-core</artifactId>
               <version>2.23.1</version>
           </dependency>
           <dependency>
               <groupId>org.apache.logging.log4j</groupId>
               <artifactId>log4j-api</artifactId>
               <version>2.23.1</version>
           </dependency>
       ...
       </dependencies>

   where ... are some other existing settings

3. Recompile project and regenerate settings for eclipse:

   mvn clean compile eclipse:eclipse

4. Add file logger named file with file appender and layout format into configuration file src/main/resources/log4j2.properties:

   1. Folder of the log file should be logs folder inside project folder
   2. Name of log file should be test.log

   e.g.:

   ...
   # Direct log messages to file
   logger.jtm.name = jtm.extra05.Log
   logger.jtm.level = info
   logger.jtm.additivity = false
   logger.jtm.appenderRefs = file, stdout
   logger.jtm.appenderRef.file.ref = file
   logger.jtm.appenderRef.stdout.ref = stdout
   ...

5. Set category filter settings in log4j2.properties file, that logger will show:

   1. INFO messages for jtm.extra10.Log class
   2. TRACE messages for jtm.extra10.Log$ExtLog class

   e.g.:

   ...
   logger.jtmExt.name = jtm.extra05.Log.ExtLog
   logger.jtmExt.level = trace
   logger.jtmExt.additivity = false
   logger.jtmExt.appenderRefs = file, stdout
   logger.jtmExt.appenderRef.file.ref = file
   logger.jtmExt.appenderRef.stdout.ref = stdout
   ...
6. Review package jtm.extra05

7. Declare and initialize class logger in Log class:

   private static final Logger log = LogManager.getLogger(Log.class);
8. Implement static methods to log trace, debug, info, warn, error, fatal which will write log messages with appropriate level, using the class logger.
9. Implement method getLogger() which returns reference to used logger

10. In nested class ExtLog declare and initialize logger:

    static final Logger log = LogManager.getLogger(ExtLog.class);
11. In internal class ExtLog implement static methods trace, debug, info, warn, error, fatal which will write log messages with appropriate level.
12. Check that unit tests are passing