> How many XML files have to be configured for this "easy to setup" backend?
As the others mentioned, Spring has not required XML config files in a long time. Spring boot requires nearly zero configuration, although it's a good idea to move out environment specific configurations out of the app. Speaking of, out of the box Spring works with yaml, properties, environment vars, command line vars, and the list goes on.
It really is a nice environment to work in, and if you don't like Java there is Kotlin which has worked fine within the stack IME. So many people only remember Java 5 and Spring where beans had to be wired up through XML configs.
Node is "simple" but today you need 3 package managers to install the dozens of small libraries needed for even a simple project
Really. When I found out express.js needs an extra library to read POST data I was stumped