Logging to one file from multiple java files

[Timmy Ryan]

Hi Guys,

I want to set up a logger that writes to one file from many different java files.
I just want to user the Logger class for now as I think thats all I need for my program.

public class Game {
 
public final Logger myLogger = Logger.getLogger("Test");
public Game theGame = new Game();
 
public static void main(String[] args) throws IOException {

  FileHandler myFileHandler = new FileHandler("temp.txt");
        myFileHandler.setFormatter(new SimpleFormatter());
        theGame.myLogger.addHandler(myFileHandler);
        theGame.myLogger.setUseParentHandlers(false);
        theGame.myLogger.setLevel(Level.FINEST);
        theGame.myLogger.severe("severe message");
}
}

How would I change the above code so that I can use myLogger in a different java file but still in the same package?
Also I want to be able to log messages from within static and non-static methods which is where I�m having the trouble at the moment.

[Hendy Setyo Mulyo]

I believe your problem can be solved by using Singleton pattern. You have to wrap your myLogger object in a Singleton class. Hence, you will use your logger wrapper in any part of any class in your application, and will output the log message into one file.

For example:

public class LoggerWrapper {
 
public static final Logger myLogger = Logger.getLogger("Test");

private static LoggerWrapper instance = null;
   
   public static LoggerWrapper getInstance() {
      if(instance == null) {
prepareLogger();
         instance = new LoggerWrapper ();
      }
      return instance;
   }
 
private static prepareLogger() {
FileHandler myFileHandler = new FileHandler("temp.txt");
        myFileHandler.setFormatter(new SimpleFormatter());
        myLogger.addHandler(myFileHandler);
        myLogger.setUseParentHandlers(false);
        myLogger.setLevel(Level.FINEST);
}
 

}

You can use your wrapper in any part of any class in your application like this:

 LoggerWrapper loggerWrapper = LoggerWrapper.getInstance();
       loggerWrapper.myLogger.severe( "Your severe message" );

[ August 20, 2008: Message edited by: Hendy Setyo Mulyo ]

[Tom Johnson]

You should move the config of the destination log file, level, formatter etc out to log4j.properties for easier maintenance. You can specify where it is using JVM arg -Djava.util.logging.config.file=mylogging.properties.

You can create another instance of Logger in another class and just use that, you dont need to use the same instance. For example:

class Other {
    private static final Logger anotherLogger = Logger.getLogger("Other");
 
    public void static myMethod() {
        anotherLogger.fine("fine level");
        anotherLogger.info("info level");
        anotherLogger.severe("severe level");
 
    }
 
     
}

Then, depending on what level you have specifed out in the properties file (default is INFO unless changed), some, none or all of the above log messages will appear.

HTH