org.springframework.context.ApplicationListener Maven / Gradle / Ivy
/*
* Copyright 2002-2021 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.context;
import java.util.EventListener;
import java.util.function.Consumer;
/**
* Interface to be implemented by application event listeners.
*
* Based on the standard {@code java.util.EventListener} interface
* for the Observer design pattern.
*
*
As of Spring 3.0, an {@code ApplicationListener} can generically declare
* the event type that it is interested in. When registered with a Spring
* {@code ApplicationContext}, events will be filtered accordingly, with the
* listener getting invoked for matching event objects only.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @param the specific {@code ApplicationEvent} subclass to listen to
* @see org.springframework.context.ApplicationEvent
* @see org.springframework.context.event.ApplicationEventMulticaster
* @see org.springframework.context.event.SmartApplicationListener
* @see org.springframework.context.event.GenericApplicationListener
* @see org.springframework.context.event.EventListener
*/
@FunctionalInterface
public interface ApplicationListener extends EventListener {
/**
* Handle an application event.
* @param event the event to respond to
*/
void onApplicationEvent(E event);
/**
* Create a new {@code ApplicationListener} for the given payload consumer.
* @param consumer the event payload consumer
* @param the type of the event payload
* @return a corresponding {@code ApplicationListener} instance
* @since 5.3
* @see PayloadApplicationEvent
*/
static ApplicationListener> forPayload(Consumer consumer) {
return event -> consumer.accept(event.getPayload());
}
}