1 /* 2 * Copyright (C) 2011 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.util.concurrent; 18 19 import com.google.common.annotations.Beta; 20 import com.google.common.base.Preconditions; 21 22 import java.util.concurrent.TimeUnit; 23 import java.util.concurrent.TimeoutException; 24 25 /** 26 * A future which forwards all its method calls to another future. Subclasses 27 * should override one or more methods to modify the behavior of the backing 28 * future as desired per the <a href= 29 * "http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 30 * 31 * <p>Most subclasses can simply extend {@link SimpleForwardingCheckedFuture}. 32 * 33 * @param <V> The result type returned by this Future's {@code get} method 34 * @param <X> The type of the Exception thrown by the Future's 35 * {@code checkedGet} method 36 * 37 * @author Anthony Zana 38 * @since 9.0 39 */ 40 @Beta 41 public abstract class ForwardingCheckedFuture<V, X extends Exception> 42 extends ForwardingListenableFuture<V> implements CheckedFuture<V, X> { 43 44 @Override 45 public V checkedGet() throws X { 46 return delegate().checkedGet(); 47 } 48 49 @Override 50 public V checkedGet(long timeout, TimeUnit unit) throws TimeoutException, X { 51 return delegate().checkedGet(timeout, unit); 52 } 53 54 @Override 55 protected abstract CheckedFuture<V, X> delegate(); 56 57 // TODO(cpovirk): Use Standard Javadoc form for SimpleForwarding* 58 /** 59 * A simplified version of {@link ForwardingCheckedFuture} where subclasses 60 * can pass in an already constructed {@link CheckedFuture} as the delegate. 61 * 62 * @since 9.0 63 */ 64 @Beta 65 public abstract static class SimpleForwardingCheckedFuture< 66 V, X extends Exception> extends ForwardingCheckedFuture<V, X> { 67 private final CheckedFuture<V, X> delegate; 68 69 protected SimpleForwardingCheckedFuture(CheckedFuture<V, X> delegate) { 70 this.delegate = Preconditions.checkNotNull(delegate); 71 } 72 73 @Override 74 protected final CheckedFuture<V, X> delegate() { 75 return delegate; 76 } 77 } 78 } 79
