Extra 10. Log4J

1. Review presentation
   

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

       <dependencies>
       ...
           <dependency>
               <groupId>log4j</groupId>
               <artifactId>log4j</artifactId>
               <version>1.2.17</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/log4j.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.:

   log4j.rootLogger=..., file
   ...
   # Direct log messages to file
   log4j.appender.file=org.apache.log4j.RollingFileAppender
   log4j.appender.file.File=logs/test.log
   log4j.appender.file.MaxFileSize=5MB
   log4j.appender.file.MaxBackupIndex=10
   log4j.appender.file.layout=org.apache.log4j.PatternLayout
   log4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{4} %M:%L - %m%n
   ...

5. Set category filter settings in log4j.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.:

   ...
   log4j.logger.jtm.extra10.Log=info
   log4j.logger.jtm.extra10.Log$ExtLog=trace
   ...
6. Review package jtm.extra10
   1. Implement class Log with methods trace, debug, info, warn, error, fatal which will write log messages with appropriate level,
   2. Implement method getLogger() which returns reference to used logger,
   3. In class Log implement internal class ExtLog which also implements static methods trace, debug, info, warn, error, fatal which will write log messages with appropriate level.
7. Check that unit tests are passing.