001/*
002 * Copyright (C) 2011 The Guava 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 * http://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 com.google.common.util.concurrent;
018
019import com.google.common.annotations.Beta;
020import com.google.common.annotations.GwtCompatible;
021
022import java.util.concurrent.ExecutionException;
023import java.util.concurrent.Future;
024
025/**
026 * Provides a backup {@code Future} to replace an earlier failed {@code Future}. An implementation
027 * of this interface can be applied to an input {@code Future} with {@link Futures#withFallback}.
028 *
029 * @param <V> the result type of the provided backup {@code Future}
030 *
031 * @author Bruno Diniz
032 * @since 14.0
033 * @deprecated This interface's main user, {@link Futures#withFallback(ListenableFuture,
034 *     FutureFallback) Futures.withFallback}, has been updated to use {@link AsyncFunction}. We
035 *     recommend that other APIs be updated in the same way. This interface will be removed in Guava
036 *     release 20.0.
037 */
038@Beta
039@Deprecated
040@GwtCompatible
041public interface FutureFallback<V> {
042  /**
043   * Returns a {@code Future} to be used in place of the {@code Future} that failed with the given
044   * exception. The exception is provided so that the {@code Fallback} implementation can
045   * conditionally determine whether to propagate the exception or to attempt to recover.
046   *
047   * @param t the exception that made the future fail. If the future's {@link Future#get() get}
048   *     method throws an {@link ExecutionException}, then the cause is passed to this method. Any
049   *     other thrown object is passed unaltered.
050   */
051  ListenableFuture<V> create(Throwable t) throws Exception;
052}