Is it possible to override values set in properties file for java.util.logging programatically?

Question

I have an application for which I want to have the logging level set to INFO unless Debug Mode is set in which case I want to set the level to FINEST.

If I set the level in the properties file it does not get overridden from the program using logger.setLevel(Level.FINEST) also, if I do not set anything for the .level field in the properties file, by default the INFO level is taken and again I cannot override to use FINEST if isDebugEnable().

How can I make this level configurable based on the condition ?

 try(InputStream configFile = getClass().getClassLoader().getResourceAsStream("logging.properties")) {
        LogManager.getLogManager().readConfiguration(configFile);
    } catch (IOException e) {
        throw new IllegalStateException("Unable to load default logging properties.", e);
    }
 if (isDebugEnabled()) {
        logger.setLevel(Level.FINEST);
    } else {
        logger.setLevel(Level.INFO);
    }

My config file is as follows:

handlers= java.util.logging.ConsoleHandler
.level= INFO

# default file output is in user's home directory.
java.util.logging.FileHandler.pattern = %h/java%u.log
java.util.logging.FileHandler.limit = 50000
java.util.logging.FileHandler.count = 1
java.util.logging.FileHandler.formatter = java.util.logging.XMLFormatter

# Enable console to set level to FINEST and above.
java.util.logging.ConsoleHandler.level = FINEST
java.util.logging.ConsoleHandler.formatter = java.util.logging.SimpleFormatter

I can do this using as follow, but would like to know if there is a better way to do this. (May be using properties file)

ConsoleHandler consoleHandler = new ConsoleHandler();
setLogLevel();
consoleHandler.setLevel(Level.FINEST);
logger.addHandler(new ConsoleHandler()); 

Answer 1

If you are setting a DEBUG option before startup of the JVM then just package a 2nd logging.properties file called debug.properties and change the java.util.logging.config.file to point to the debug.properties when you want debug options.

handlers= java.util.logging.ConsoleHandler
.level= FINEST

# default file output is in user's home directory.
java.util.logging.FileHandler.pattern = %h/java%u.log
java.util.logging.FileHandler.level = ALL
java.util.logging.FileHandler.limit = 50000
java.util.logging.FileHandler.count = 1
java.util.logging.FileHandler.formatter = java.util.logging.XMLFormatter

# Enable console to set level to show all levels.
java.util.logging.ConsoleHandler.level = ALL
java.util.logging.ConsoleHandler.formatter = java.util.logging.SimpleFormatter

If you have to set the levels at runtime you'll run in to problems with readConfiguration not resetting all everything after boot of the JVM. Under JDK 8 or older all you can do is call readConfiguration to populate the defaults and add more code to fix the broken behavior. Since you just need to set the level on handlers then just add that code.

try(InputStream configFile = getClass().getClassLoader().getResourceAsStream("logging.properties")) {
    LogManager.getLogManager().readConfiguration(configFile);
} catch (IOException e) {
    throw new IllegalStateException("Unable to load default logging properties.", e);
}

Level lvl;
if (isDebugEnabled()) {
    lvl = Level.FINEST;
} else {
    lvl = Level.INFO;
}
logger.setLevel(lvl);
for(Handler h : logger.getHandlers()) {
    h.setLevel(lvl);
}

JDK 9 provides an updateConfiguration method that will work around the broken behavior of the readConfiguration method.