When using the KeycloakOIDCFilter servlet filter a KeycloakConfigResolver is used internally to configure KeyCloak access. Currently only a class for a KeycloakConfigResolver can be defined and no instance.
Sometimes you want to do something like this:
KeycloakConfigResolver myCustomResolver = ...
KeycloakOIDCFilter filter = new KeycloakOIDCFilter(myCustomResolver)
FilterRegistration.Dynamic keycloakSecurityFilter = servletContext.addFilter(FILTER_NAME, filter);