001/*
002 * Copyright 2002-2019 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.context;
018
019import java.util.EventListener;
020
021/**
022 * Interface to be implemented by application event listeners.
023 *
024 * <p>Based on the standard {@code java.util.EventListener} interface
025 * for the Observer design pattern.
026 *
027 * <p>As of Spring 3.0, an {@code ApplicationListener} can generically declare
028 * the event type that it is interested in. When registered with a Spring
029 * {@code ApplicationContext}, events will be filtered accordingly, with the
030 * listener getting invoked for matching event objects only.
031 *
032 * @author Rod Johnson
033 * @author Juergen Hoeller
034 * @param <E> the specific {@code ApplicationEvent} subclass to listen to
035 * @see org.springframework.context.ApplicationEvent
036 * @see org.springframework.context.event.ApplicationEventMulticaster
037 * @see org.springframework.context.event.EventListener
038 */
039@FunctionalInterface
040public interface ApplicationListener<E extends ApplicationEvent> extends EventListener {
041
042        /**
043         * Handle an application event.
044         * @param event the event to respond to
045         */
046        void onApplicationEvent(E event);
047
048}