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.lang.Nullable;
023
024/**
025 * Extended variant of the standard {@link ApplicationListener} interface,
026 * exposing further metadata such as the supported event and source type.
027 *
028 * <p>For full introspection of generic event types, consider implementing
029 * the {@link GenericApplicationListener} interface instead.
030 *
031 * @author Juergen Hoeller
032 * @since 3.0
033 * @see GenericApplicationListener
034 * @see GenericApplicationListenerAdapter
035 */
036public interface SmartApplicationListener extends ApplicationListener<ApplicationEvent>, Ordered {
037
038        /**
039         * Determine whether this listener actually supports the given event type.
040         * @param eventType the event type (never {@code null})
041         */
042        boolean supportsEventType(Class<? extends ApplicationEvent> eventType);
043
044        /**
045         * Determine whether this listener actually supports the given source type.
046         * <p>The default implementation always returns {@code true}.
047         * @param sourceType the source type, or {@code null} if no source
048         */
049        default boolean supportsSourceType(@Nullable Class<?> sourceType) {
050                return true;
051        }
052
053        /**
054         * Determine this listener's order in a set of listeners for the same event.
055         * <p>The default implementation returns {@link #LOWEST_PRECEDENCE}.
056         */
057        @Override
058        default int getOrder() {
059                return LOWEST_PRECEDENCE;
060        }
061
062}