javaloggingjava.util.logging

Why are the Level.FINE logging messages not showing?

The JavaDocs for java.util.logging.Level state:

The levels in descending order are:

Source

import java.util.logging.*;

class LoggingLevelsBlunder {

    public static void main(String[] args) {
        Logger logger = Logger.getAnonymousLogger();
        logger.setLevel(Level.FINER);
        System.out.println("Logging level is: " + logger.getLevel());
        for (int ii=0; ii<3; ii++) {
            logger.log(Level.FINE, ii + " " + (ii*ii));
            logger.log(Level.INFO, ii + " " + (ii*ii));
        }
    }
}

Output

Logging level is: FINER
Jun 11, 2011 9:39:23 PM LoggingLevelsBlunder main
INFO: 0 0
Jun 11, 2011 9:39:24 PM LoggingLevelsBlunder main
INFO: 1 1
Jun 11, 2011 9:39:24 PM LoggingLevelsBlunder main
INFO: 2 4
Press any key to continue . . .

Problem statement

My example sets the Level to FINER, so I was expecting to see 2 messages for each loop. Instead I see a single message for each loop (the Level.FINE messages are missing).

Question

What needs changing in order to see the FINE (, FINER or FINEST) output?

Update (solution)

Thanks to Vineet Reynolds' answer, this version works according to my expectation. It displays 3 x INFO messages, & 3 x FINE messages.

import java.util.logging.*;

class LoggingLevelsBlunder {

    public static void main(String[] args) {
        Logger logger = Logger.getAnonymousLogger();
        // LOG this level to the log
        logger.setLevel(Level.FINER);

        ConsoleHandler handler = new ConsoleHandler();
        // PUBLISH this level
        handler.setLevel(Level.FINER);
        logger.addHandler(handler);

        System.out.println("Logging level is: " + logger.getLevel());
        for (int ii=0; ii<3; ii++) {
            logger.log(Level.FINE, ii + " " + (ii*ii));
            logger.log(Level.INFO, ii + " " + (ii*ii));
        }
    }
}
Solution

  • Loggers only log the message, i.e. they create the log records (or logging requests). They do not publish the messages to the destinations, which is taken care of by the Handlers. Setting the level of a logger, only causes it to create log records matching that level or higher.

    You might be using a ConsoleHandler (I couldn't infer where your output is System.err or a file, but I would assume that it is the former), which defaults to publishing log records of the level Level.INFO. You will have to configure this handler, to publish log records of level Level.FINER and higher, for the desired outcome.

    I would recommend reading the Java Logging Overview guide, in order to understand the underlying design. The guide covers the difference between the concept of a Logger and a Handler.

    Editing the handler level

    1. Using the Configuration file

    The java.util.logging properties file (by default, this is the logging.properties file in JRE_HOME/lib) can be modified to change the default level of the ConsoleHandler:

    java.util.logging.ConsoleHandler.level = FINER

    2. Creating handlers at runtime

    This is not recommended, for it would result in overriding the global configuration. Using this throughout your code base will result in a possibly unmanageable logger configuration.

    Handler consoleHandler = new ConsoleHandler();
consoleHandler.setLevel(Level.FINER);
Logger.getAnonymousLogger().addHandler(consoleHandler);