java - How to dynamically change log level in SLF4j OR Log4J

Question

Recently I encountered a situtation where Application Loglevel changes dynamically. Application Admin can set it to INFO/DEBUG/ WARN from front end. Based on the log level choosen be him application logging must be changed.

I am sure loggers support this scenario, but not sure how can I achive this. If any of you have idea/thoughts on this please let me know.

Thanks in advance for your help.

-Narendra

Answer 1

It is not possible to change the log level dynamically in slf4j, but some backends for slf4j support it, including log4j.

This solution worked for me:

org.apache.log4j.Logger logger4j = org.apache.log4j.Logger.getRootLogger();
logger4j.setLevel(org.apache.log4j.Level.toLevel("ERROR"));

(Source: http://prateep.info/2015/12/12/Dynamically-change-log-level-in-SLF4j-Log4J-with-Standalone-Java-Class/)

The disadvantage of this solution is that it uses the backend directly, which you're not supposed to do when using slf4j because the point of slf4j is to provide an abstraction away from the specific backend you're using.