Event publishing with ApplicationEventPublisher in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is ApplicationEventPublisher in Spring Boot?

It is a Spring interface used to publish events to listeners within the application context. It helps components communicate by sending and receiving events.

beginner

How do you publish a custom event using ApplicationEventPublisher?

You create a custom event class, inject ApplicationEventPublisher in your component, then call publishEvent(yourEvent) to send the event.

beginner

What annotation is used to listen for events published by ApplicationEventPublisher?

The @EventListener annotation marks a method to listen for specific events published in the application context.

intermediate

Why use events and ApplicationEventPublisher instead of direct method calls?

Events decouple components, allowing them to communicate without knowing each other directly. This improves modularity and flexibility.

intermediate

What happens if no listener is registered for an event published with ApplicationEventPublisher?

The event is published but no action occurs. Spring does not throw an error if no listener handles the event.

Which method is used to publish an event with ApplicationEventPublisher?

A sendEvent()

B fireEvent()

C publishEvent()

D triggerEvent()

The correct method to publish events is publishEvent().

Which annotation marks a method to listen for Spring events?

A @EventListener

B @OnEvent

C @Subscribe

D @ListenEvent

Spring uses @EventListener to mark event listener methods.

What must you do before publishing a custom event?

A Annotate the event class with @Event

B Register the event in XML config

C Implement EventPublisher interface

D Create a class extending ApplicationEvent or any object

You create a custom event class, often extending ApplicationEvent or using any object as event payload.

What is a key benefit of using events in Spring Boot?

A Decoupling components for better modularity

B Faster database queries

C Automatic UI updates

D Simplifies multithreading

Events help decouple components, making the app easier to maintain and extend.

If no listener is registered for an event, what happens when it is published?

A An exception is thrown

B The event is ignored silently

C The application crashes

D The event is queued for later

Spring silently ignores events with no listeners; no error occurs.

Explain how to publish and listen to a custom event using ApplicationEventPublisher in Spring Boot.

Think about the steps from creating the event to handling it.

Describe the advantages of using event publishing with ApplicationEventPublisher over direct method calls.

Consider how events help components work independently.