001/*
002 * Copyright 2002-2018 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.event;
018
019import org.springframework.context.ApplicationEvent;
020import org.springframework.context.ApplicationListener;
021import org.springframework.core.Ordered;
022import org.springframework.core.ResolvableType;
023import org.springframework.lang.Nullable;
024
025/**
026 * Extended variant of the standard {@link ApplicationListener} interface,
027 * exposing further metadata such as the supported event and source type.
028 *
029 * <p>As of Spring Framework 4.2, this interface supersedes the Class-based
030 * {@link SmartApplicationListener} with full handling of generic event types.
031 *
032 * @author Stephane Nicoll
033 * @since 4.2
034 * @see SmartApplicationListener
035 * @see GenericApplicationListenerAdapter
036 */
037public interface GenericApplicationListener extends ApplicationListener<ApplicationEvent>, Ordered {
038
039        /**
040         * Determine whether this listener actually supports the given event type.
041         * @param eventType the event type (never {@code null})
042         */
043        boolean supportsEventType(ResolvableType eventType);
044
045        /**
046         * Determine whether this listener actually supports the given source type.
047         * <p>The default implementation always returns {@code true}.
048         * @param sourceType the source type, or {@code null} if no source
049         */
050        default boolean supportsSourceType(@Nullable Class<?> sourceType) {
051                return true;
052        }
053
054        /**
055         * Determine this listener's order in a set of listeners for the same event.
056         * <p>The default implementation returns {@link #LOWEST_PRECEDENCE}.
057         */
058        @Override
059        default int getOrder() {
060                return LOWEST_PRECEDENCE;
061        }
062
063}