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.util.concurrent;
018
019import java.util.concurrent.CompletableFuture;
020import java.util.concurrent.Future;
021
022/**
023 * Extend {@link Future} with the capability to accept completion callbacks.
024 * If the future has completed when the callback is added, the callback is
025 * triggered immediately.
026 *
027 * <p>Inspired by {@code com.google.common.util.concurrent.ListenableFuture}.
028 *
029 * @author Arjen Poutsma
030 * @author Sebastien Deleuze
031 * @author Juergen Hoeller
032 * @since 4.0
033 * @param <T> the result type returned by this Future's {@code get} method
034 */
035public interface ListenableFuture<T> extends Future<T> {
036
037        /**
038         * Register the given {@code ListenableFutureCallback}.
039         * @param callback the callback to register
040         */
041        void addCallback(ListenableFutureCallback<? super T> callback);
042
043        /**
044         * Java 8 lambda-friendly alternative with success and failure callbacks.
045         * @param successCallback the success callback
046         * @param failureCallback the failure callback
047         * @since 4.1
048         */
049        void addCallback(SuccessCallback<? super T> successCallback, FailureCallback failureCallback);
050
051
052        /**
053         * Expose this {@link ListenableFuture} as a JDK {@link CompletableFuture}.
054         * @since 5.0
055         */
056        default CompletableFuture<T> completable() {
057                CompletableFuture<T> completable = new DelegatingCompletableFuture<>(this);
058                addCallback(completable::complete, completable::completeExceptionally);
059                return completable;
060        }
061
062}