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In Grails versions earlier than 3.3, Grails used Reactor 2.x which provided `@Consumer` and `@Selector` annotations to listen for events. For example:

[source,groovy]
----
import reactor.spring.context.annotation.*

@Consumer
class MyService {
	@Selector('myEvent')
	void myEventListener(Object data) {
		println "GOT EVENT $data"
	}
}
----

Within the `grails-events-compat` dependency Grails 3.3 and above ship versions of these annotations that bridge and provide compatibility for applications upgrading to Grails 3.3, however these annotations are considered deprecated and the link:{api}grails/events/annotation/Subscriber.html[Subscriber] annotation should be used instead which provides equivalent functionality.