Spring Boot >= 2.3

[dimovelev]

The idea is still relevant for newer spring boot application. There however you can just switch the readiness like that:
AvailabilityChangeEvent.publish(ctx, ReadinessState.REFUSING_TRAFFIC);. Provided that you use the /actuator/health/readiness for health-checking your application and having the spring graceful shutdown enabled, this would work pretty well. I personally am still using a hook just to let the load-balancers remove me from the pool first, before i start rejecting traffic with 503 (what spring graceful shutdown does out of the box).