Set Logging Level in Spring Boot via Environment Variable

Question

Should it be possible to set logging levels through environment variables alone in a Spring Boot application?

I don\'t want to use application.properties

Answer 1

Setting log levels via environment variables can only be done for Packages but not for Classes

I had the same problem as the OP. And I was wondering why some of the users here reported that the proposed solutions worked well while others responded they didn't.
I'm on Spring Boot 2.1 and the problem obviously changed a bit over the last years, but the current situation is as follows:

TL;DR

Setting the log level for a package works:

LOGGING_LEVEL_COM_ACME_PACKAGE=DEBUG

While setting the log level for a specific class has no effect:

LOGGING_LEVEL_COM_ACME_PACKAGE_CLASS=DEBUG

How can that be?

Have a look at Spring Boot's LoggingApplicationListener.
If you'd debug it and set a breakpoint in the highlighted code block, you'd see that the log level definition for a class com.acme.mypackage.MyClass becomes com.acme.mypackage.myclass.
So a log level definition for a class looks exactly like a log level definition for a package.

This is related to Spring's Relaxed Binding, which proposes an upper case notation for environment variables. Thus the typical camel case notation of a class is not available for the LoggingApplicationListener. On the other hand, I think one can't check whether the given fully-qualified path matches a class. The classloader won't find anything as long as the notation doesn't match exactly.

Thus log definitions in environment variables don't work for classes but only for packages.