23.5 Application events and listeners

In addition to the usual Spring Framework events, such as ContextRefreshedEvent, a SpringApplication sends some additional application events.

	Note
Some events are actually triggered before the ApplicationContext is created so you cannot register a listener on those as a @Bean. You can register them via the SpringApplication.addListeners(…​) or SpringApplicationBuilder.listeners(…​) methods.

Application events are sent in the following order, as your application runs:

1. An ApplicationStartedEvent is sent at the start of a run, but before any processing except the registration of listeners and initializers.
2. An ApplicationEnvironmentPreparedEvent is sent when the Environment to be used in the context is known, but before the context is created.
3. An ApplicationPreparedEvent is sent just before the refresh is started, but after bean definitions have been loaded.
4. An ApplicationReadyEvent is sent after the refresh and any related callbacks have been processed to indicate the application is ready to service requests.
5. An ApplicationFailedEvent is sent if there is an exception on startup.

	Tip
You often won’t need to use application events, but it can be handy to know that they exist. Internally, Spring Boot uses events to handle a variety of tasks.