code: public static Config setContextFilterClass(Config config, Class<? extends ContextFilter> klazz) {
      return config.withValue(CONTEXT_FILTER_CLASS, ConfigValueFactory.fromAnyRef(klazz.getCanonicalName()));
    }
docs: Modify the configuration to set the {@link ContextFilter} class.
  @param config Input {@link Config}.
  @param klazz Class of desired {@link ContextFilter}.
  @return Modified {@link Config}.