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
17package com.google.common.util.concurrent;
18
19import com.google.common.annotations.Beta;
20import com.google.common.base.Preconditions;
21
22import java.util.concurrent.TimeUnit;
23import 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
41public 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