How do ApplicationContext events work, and how do you run code at the right moment during startup/shutdown?

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Startup hook ladder: constructor (wiring only) → @PostConstruct (cheap self-setup) → ContextRefreshedEvent (context assembled) → ApplicationReadyEvent (Boot: ready to serve — warm caches, start consumers here) → SmartLifecycle.start() (when you need ordered phases and graceful stop symmetry).
Shutdown mirror: ContextClosedEvent → SmartLifecycle.stop(phases in reverse) → @PreDestroy → destroy methods. Graceful shutdown = stop intake first (web server pauses, listeners stop), then drain, then close pools — phases exist exactly for this ordering.
Domain events: publisher.publishEvent(new OrderPlaced(id)) decouples modules in a monolith; @TransactionalEventListener(phase = AFTER_COMMIT) prevents the classic 'email sent but transaction rolled back' bug.
Sync-by-default matters: listeners run on the caller's thread inside its transaction unless you opt out — both a feature (consistency) and a latency trap.

After-commit event — the outbox's little brother

@Service
class CheckoutService {
    @Transactional
    public void checkout(Cart cart) {
        var order = repo.save(Order.from(cart));
        events.publishEvent(new OrderPlaced(order.id()));   // buffered…
    }
}

@Component
class NotificationListener {
    @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
    void on(OrderPlaced e) { mailer.confirm(e.orderId()); } // …fires only on commit
}

How do ApplicationContext events work, and how do you run code at the right moment during startup/shutdown?

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