@Bean
    public HealthChecker jettyHealthChecker(ServletWebServerApplicationContext applicationContext) {
        final Server server = jettyServer(applicationContext).getServer();
        return server::isRunning;
    }
Returns a new {@link HealthChecker} that marks the server as unhealthy when Tomcat becomes unavailable.
examples/spring-boot-jetty/src/main/java/example/springframework/boot/jetty/HelloConfiguration.java