/*
 * Copyright 2002-2020 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 java.util.EventListener interface for the Observer design pattern. 
As of Spring 3.0, an ApplicationListener can generically declare the event type that it is interested in. When registered with a Spring ApplicationContext, events will be filtered accordingly, with the listener getting invoked for matching event objects only. 
Author:
Rod Johnson, Juergen Hoeller
Type parameters:
<E> – the specific ApplicationEvent subclass to listen to
See Also:
ApplicationEvent
ApplicationEventMulticaster
EventListener/**
 * Interface to be implemented by application event listeners.
 *
 * <p>Based on the standard {@code java.util.EventListener} interface
 * for the Observer design pattern.
 *
 * <p>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 <E> the specific {@code ApplicationEvent} subclass to listen to
 * @see org.springframework.context.ApplicationEvent
 * @see org.springframework.context.event.ApplicationEventMulticaster
 * @see org.springframework.context.event.EventListener
 */
@FunctionalInterface
public interface ApplicationListener<E extends ApplicationEvent> extends EventListener {

	
Handle an application event.
Params:
event – the event to respond to/**
	 * Handle an application event.
	 * @param event the event to respond to
	 */
	void onApplicationEvent(E event);


	
Create a new ApplicationListener for the given payload consumer. 
Params:
consumer – the event payload consumer
Type parameters:
<T> – the type of the event payload
See Also:
PayloadApplicationEvent
Returns:
a corresponding ApplicationListener instance
Since:
5.3/**
	 * Create a new {@code ApplicationListener} for the given payload consumer.
	 * @param consumer the event payload consumer
	 * @param <T> the type of the event payload
	 * @return a corresponding {@code ApplicationListener} instance
	 * @since 5.3
	 * @see PayloadApplicationEvent
	 */
	static <T> ApplicationListener<PayloadApplicationEvent<T>> forPayload(Consumer<T> consumer) {
		return event -> consumer.accept(event.getPayload());
	}

}