How to find which library slf4j has bound itself to?

46
votes

I am using slf4j for logging in my application. I get the purpose of slf4j. I would like to know how to find out which logging-library slf4j is currently binding to. I have log4j in my referenced libraries. I am assuming that slf4j has bound itself to log4j.

What I would like to know is, is there any way to explicitly confirm this binding?

4
javalogginglog4jslf4j
I swear there was a way to turn on slf4j debugging (meta debugging) but I can't remember what it was. None of the answers address that. – Sridhar Sarnobat

4 Answers

61
votes

Just do what SLF4J does to discover the binding:

final StaticLoggerBinder binder = StaticLoggerBinder.getSingleton();

Now you can try to find out what is the actual implementation in my case:

System.out.println(binder.getLoggerFactory());
System.out.println(binder.getLoggerFactoryClassStr());

This prints:

ch.qos.logback.classic.LoggerContext[default]
ch.qos.logback.classic.selector.DefaultContextSelector
8
votes

The StaticLoggerBinder's getLoggerFactoryClassStr() method is probably what you're looking for.

3
votes

Easy. Put a breakpoint on .. say.. LOG.info(...). Once debugger stops there, step into.. and viola.. you will find yourself in the code of the actual logger... say log4j or logback.. whatever.

2
votes

It's possible to do this using the main slf4j public API (i.e. without the internal StaticLoggerBinder), e.g. to detect if slf4j has bpound to log4j2:

if ("org.apache.logging.slf4j.Log4jLoggerFactory".equals(
    org.slf4j.LoggerFactory.getILoggerFactory().getClass().getName()
) 
{ ... }