Vaadin 8 + Keycloak?

I have a small Vaadin app that I want to secure with Keycloak. This isn’t a Springboot app or something and I also don’t use Spring Security, documentation is therefor scarce. I did managed to secure a small Springboot app though and I thought I could sort of copy/paste []
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( this to Vaadin but alas… Does anyone here have any experience with this? It’s rather shocking that there is absolutely no documentation on this.

The main issue i’m stuck on is that my Tomcat log tells me this;

“Cannot configure an authenticator for method KEYCLOAK”
So in my web.xml I defined

patientportal-login-test /test member KEYCLOAK testing member When I change KEYCLOAK to BASIC, it prompts for logincredentials but not through Keycloak, but instead with a small popup that you normally see when auth-method is set to BASIC. Also, the credentials I enter and should work, don't.

And that’s where it fails apparently. Help