Include external JAR


I have seen various posts on how to include an external jar into your own project.
Have tried multiple solutions by creating a libs folder in the root or by creating a WEB-INF folder with lib and in there the jar files. But for probably a very obvious reason this does not seem to work. Most likely I place the JAR in the wrong location. I have tried it in intellij with either Gradle and Maven using the Vaadin build structure.

Can someone explain to me according to the root of a project where to place the jar files?

I have created a example project here: