Why this Spring application with java-based configuration don't work properly

Question

I started recently a project with the Spring framework with the ojective to develop it without none XML config file, only Java code.

In this current moment, I add th

Answer 1

I had a class

MyContextLoaderListener extends ContextLoaderListener

somewhere in my code. It was unused. Spring boot apparently used reflection to find it. I deleted the file and the problem was gone