Hi @KlausFriese,
Looking at your use case, I think you should be able to utlize the Java Authentication SDK - https://github.com/okta/okta-auth-java
This section explains the use cases of this library - https://github.com/okta/okta-auth-java#is-this-library-right-for-me
Take a look at it and decide if it’s the right one for your needs