1/*
2 * Copyright (C) 2008 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;
20
21import java.util.concurrent.CancellationException;
22import java.util.concurrent.ExecutionException;
23import java.util.concurrent.TimeUnit;
24import java.util.concurrent.TimeoutException;
25
26/**
27 * A delegating wrapper around a {@link ListenableFuture} that adds support for
28 * the {@link #checkedGet()} and {@link #checkedGet(long, TimeUnit)} methods.
29 *
30 * @author Sven Mawson
31 * @since 1.0
32 */
33@Beta
34public abstract class AbstractCheckedFuture<V, X extends Exception>
35    extends ForwardingListenableFuture.SimpleForwardingListenableFuture<V>
36    implements CheckedFuture<V, X> {
37  /**
38   * Constructs an {@code AbstractCheckedFuture} that wraps a delegate.
39   */
40  protected AbstractCheckedFuture(ListenableFuture<V> delegate) {
41    super(delegate);
42  }
43
44  /**
45   * Translates from an {@link InterruptedException},
46   * {@link CancellationException} or {@link ExecutionException} thrown by
47   * {@code get} to an exception of type {@code X} to be thrown by
48   * {@code checkedGet}. Subclasses must implement this method.
49   *
50   * <p>If {@code e} is an {@code InterruptedException}, the calling
51   * {@code checkedGet} method has already restored the interrupt after catching
52   * the exception. If an implementation of {@link #mapException(Exception)}
53   * wishes to swallow the interrupt, it can do so by calling
54   * {@link Thread#interrupted()}.
55   *
56   * <p>Subclasses may choose to throw, rather than return, a subclass of
57   * {@code RuntimeException} to allow creating a CheckedFuture that throws
58   * both checked and unchecked exceptions.
59   */
60  protected abstract X mapException(Exception e);
61
62  /**
63   * {@inheritDoc}
64   *
65   * <p>This implementation calls {@link #get()} and maps that method's standard
66   * exceptions to instances of type {@code X} using {@link #mapException}.
67   *
68   * <p>In addition, if {@code get} throws an {@link InterruptedException}, this
69   * implementation will set the current thread's interrupt status before
70   * calling {@code mapException}.
71   *
72   * @throws X if {@link #get()} throws an {@link InterruptedException},
73   *         {@link CancellationException}, or {@link ExecutionException}
74   */
75  @Override
76  public V checkedGet() throws X {
77    try {
78      return get();
79    } catch (InterruptedException e) {
80      Thread.currentThread().interrupt();
81      throw mapException(e);
82    } catch (CancellationException e) {
83      throw mapException(e);
84    } catch (ExecutionException e) {
85      throw mapException(e);
86    }
87  }
88
89  /**
90   * {@inheritDoc}
91   *
92   * <p>This implementation calls {@link #get(long, TimeUnit)} and maps that
93   * method's standard exceptions (excluding {@link TimeoutException}, which is
94   * propagated) to instances of type {@code X} using {@link #mapException}.
95   *
96   * <p>In addition, if {@code get} throws an {@link InterruptedException}, this
97   * implementation will set the current thread's interrupt status before
98   * calling {@code mapException}.
99   *
100   * @throws X if {@link #get()} throws an {@link InterruptedException},
101   *         {@link CancellationException}, or {@link ExecutionException}
102   * @throws TimeoutException {@inheritDoc}
103   */
104  @Override
105  public V checkedGet(long timeout, TimeUnit unit) throws TimeoutException, X {
106    try {
107      return get(timeout, unit);
108    } catch (InterruptedException e) {
109      Thread.currentThread().interrupt();
110      throw mapException(e);
111    } catch (CancellationException e) {
112      throw mapException(e);
113    } catch (ExecutionException e) {
114      throw mapException(e);
115    }
116  }
117}
118