The SLF4J (Simple Logging Facade for Java) is used for logging. The SLF4J detects and uses the concrete logging implementation configured by user. By default, the Logback logging implementation is recommended.
The Logback (or any other logging implementation) must be configured at the beginning of the application lifecycle.
The examples of Logback configurations can be found in the Samples module.
The details of Logback configuration can be found here.