Changing log levels in Log4j2

How do you change log levels in Log4j 2 when the Logger API does not have a setLevel() method?

The Configurator class provides several methods to change levels in Log4j. An important feature to understand before using these APIs is that logger names are hierarchical, see Refining Logging with Hierarchical Loggers.

Configurator.setAllLevels(String, Level)

The Configurator.setAllLevels(String, Level) method sets the level of the given named logger and all child loggers. Recall that in Log4j, loggers are hierachical. If you have the loggers, and, and you call setAllLevels("", Level.DEBUG) then all the loggers I listed will be set to DEBUG as will "". A logger "" will remain as is.

Configurator.setLevel(Map<String, Level>)

The method Configurator.setLevel(Map<String, Level>) will set each named logger to its Level from the map. No child loggers will be affected unlike setAllLevels(String, Level).

For example:

Map&amp;lt;String, Level&amp;gt; map = new HashMap&amp;lt;&amp;gt;();
map.put(&quot;;, Level.DEBUG);
map.put(&quot;;, Level.DEBUG);

This will set the loggers "" and "" to DEBUG but no existing child loggers of either will be affected. If you create a new child logger though, that child logger will inherit its level from its parent.

Configurator.setLevel(String, Level)

The method Configurator.setLevel(String, Level) sets the named logger to the given level without affecting child loggers (unlike setAllLevels(String, Level)).


Finally, Configurator.setRootLevel(Level) sets the level of the root logger to the given level without affecting child loggers. The root logger is the topmost logger with a name of "" (the empty string).

Happy Coding,
Gary Gregory

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