Java Logging: Configuration

Jakob Jenkov
Last update: 2014-08-07

The Java Logging API can be configured in two ways:

  1. Via a configuration class.
  2. Via a configuration file.

The initialization of the configuration is taken care of by the java.util.logging.LogManager class.

Configuration Class

You can use a Java class to configure the Java Logging API. You do so by specifying the name of the class in the JVM parameter java.util.logging.config.class. It is the constructor of that class that should load the configuration and apply it to the Logger's in the hierarchy.

Configuration File

If no configuration class is specified, you can instead specify a configuration file (but no configuration class can be specified then!).

The Java Logging API has a default logging configuration file located at "lib/", inside the JRE directory. If you edit this file, you edit the default logging settings for the entire JRE, for every program executed. This is most often not what you want to do, though.

Instead, you can set a separate configuration file for your application. You do so by setting the JVM property java.util.logging.config.file to point to this file.

The configuration file is a standard property file as you know them from Java. Inside this property file you can set properties that configure the various Logger's and Handler's used in your application.

Here is a list of properties you can set in the configuration file. You should double check the JavaDoc over time to see if any of this changes (e.g. in a later version of Java than Java 6).

Property Description
handlers A white space or comma separated list of handler class names to be added to the root Logger
config A white space or comma separated list of class names which will be instantiated when the LogManager is initialized. The constructors of these classes can execute arbitrary configuration code.
"logger".handlers Sets the handler classes to use for a given Logger in the hierarchy. Replace the "logger" with a specific name of a Logger in your app (e.g. com.jenkov.web).
"logger".useParentHandlers Tells a given Logger whether it should log to its parents or not (true or false).
"logger".level Tells a given Logger what minimum log level it should log.
java.util.logging.FileHandler.level Sets the default log level for all FileHandler's.
java.util.logging.FileHandler.filter A class name of the Filter to use on all FileHandler's.
java.util.logging.FileHandler.formatter A class name of the Formatter to use on all FileHandler's.
java.util.logging.FileHandler.encoding The encoding to use by all FileHandler's (e.g. UTF-8, UTF-16 etc.).
java.util.logging.FileHandler.limit The approximate amount of bytes to write to a log file, before rotating to a new file.
java.util.logging.FileHandler.count The number of log files to use in the log file rotation.
java.util.logging.FileHandler.append Sets whether or not the FileHandler's should append to an existing file or not (true or false), if an existing log file is found.
java.util.logging.FileHandler.pattern The log file name pattern.
java.util.logging.ConsoleHandler.level Sets the default log level of all ConsoleHandler's.
java.util.logging.ConsoleHandler.filter Sets the Filter to use by all ConsoleHandler's
java.util.logging.ConsoleHandler.formatter Sets the Formatter to use by all ConsoleHandler's.
java.util.logging.ConsoleHandler.encoding Sets the encoding to use by all ConsoleHandler's.
java.util.logging.StreamHandler.level Sets the default log level of all StreamHandler's.
java.util.logging.StreamHandler.filter Sets the Filter to use by all StreamHandler's
java.util.logging.StreamHandler.formatter Sets the Formatter to use by all StreamHandler's.
java.util.logging.StreamHandler.encoding Sets the encoding to use by all StreamHandler's.
java.util.logging.SocketHandler.level Sets the default log level of all SocketHandler's.
java.util.logging.SocketHandler.filter Sets the Filter to use by all SocketHandler's.
java.util.logging.SocketHandler.formatter Sets the Formatter to use by all SocketHandler's.
java.util.logging.SocketHandler.encoding Sets the encoding to use by all SocketHandler's. Sets the host name of the host to send the log messages to (e.g.
java.util.logging.SocketHandler.port Sets the port number of of the host to send the log message to (e.g. 9999).
java.util.logging.MemoryHandler.level Sets the default log level of all MemoryHandler's.
java.util.logging.MemoryHandler.filter Sets the Filter to use by all MemoryHandler's.
java.util.logging.MemoryHandler.size The size of the internal LogRecord buffer.
java.util.logging.MemoryHandler.push The push level of messages causing the buffer to be pushed to the target Handler. Defaults to SEVERE. The class name of the target Handler.

Here is an example configuration file. Not all properties are set to a value. You should do that in your own configuration file, or omit the configuration parameter if it has no value.

Note: Configuration properties are applied in the sequence they are listed in the config file. That means, that you should configure parent Logger's before child Logger's. Otherwise the configuration of the parent Logger will override that of the child Logger.

handlers = java.util.logging.FileHandler
config   =

"logger".handlers           =
"logger".useParentHandlers  =
"logger".level              =

java.util.logging.FileHandler.level     = WARNING
java.util.logging.FileHandler.filter    =
java.util.logging.FileHandler.formatter =
java.util.logging.FileHandler.encoding  =
java.util.logging.FileHandler.limit     =
java.util.logging.FileHandler.count     =
java.util.logging.FileHandler.append    = false
java.util.logging.FileHandler.pattern   = log.%u.%g.txt

java.util.logging.ConsoleHandler.level     = WARNING
java.util.logging.ConsoleHandler.filter    =
java.util.logging.ConsoleHandler.formatter =
java.util.logging.ConsoleHandler.encoding  =
java.util.logging.StreamHandler.level     = WARNING
java.util.logging.StreamHandler.filter    =
java.util.logging.StreamHandler.formatter =
java.util.logging.StreamHandler.encoding  =

java.util.logging.SocketHandler.level     = WARNING
java.util.logging.SocketHandler.filter    =
java.util.logging.SocketHandler.formatter =
java.util.logging.SocketHandler.encoding  =      =
java.util.logging.SocketHandler.port      =

java.util.logging.MemoryHandler.level     = WARNING
java.util.logging.MemoryHandler.filter    =
java.util.logging.MemoryHandler.size      =
java.util.logging.MemoryHandler.push      =    =

Jakob Jenkov

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