[keycloak-user] How to secure JAX-RS service based on reasteasy running on undertow

Hi everybody, I configured keycloak with mongodb, then I secured frontend on Tomcat making an adapter. I need to secure backend, it is an JAX-RS service based on resteasy and running on undertow. I do not use EJB so I need some help to figure out the best way to implement security with keycloak in my scenario. Suggestions? -- Davide