001/*
002 * Copyright (C) 2008 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.util.concurrent;
016
017import com.google.common.annotations.Beta;
018import com.google.common.annotations.GwtIncompatible;
019import com.google.errorprone.annotations.CanIgnoreReturnValue;
020import java.util.concurrent.CancellationException;
021import java.util.concurrent.ExecutionException;
022import java.util.concurrent.TimeUnit;
023import java.util.concurrent.TimeoutException;
024
025/**
026 * A delegating wrapper around a {@link ListenableFuture} that adds support for the {@link
027 * #checkedGet()} and {@link #checkedGet(long, TimeUnit)} methods.
028 *
029 * @author Sven Mawson
030 * @since 1.0
031 */
032@Beta
033@GwtIncompatible
034public abstract class AbstractCheckedFuture<V, X extends Exception>
035    extends ForwardingListenableFuture.SimpleForwardingListenableFuture<V>
036    implements CheckedFuture<V, X> {
037  /**
038   * Constructs an {@code AbstractCheckedFuture} that wraps a delegate.
039   */
040  protected AbstractCheckedFuture(ListenableFuture<V> delegate) {
041    super(delegate);
042  }
043
044  /**
045   * Translates from an {@link InterruptedException}, {@link CancellationException} or {@link
046   * ExecutionException} thrown by {@code get} to an exception of type {@code X} to be thrown by
047   * {@code checkedGet}. Subclasses must implement this method.
048   *
049   * <p>If {@code e} is an {@code InterruptedException}, the calling {@code checkedGet} method has
050   * already restored the interrupt after catching the exception. If an implementation of {@link
051   * #mapException(Exception)} wishes to swallow the interrupt, it can do so by calling {@link
052   * Thread#interrupted()}.
053   *
054   * <p>Subclasses may choose to throw, rather than return, a subclass of {@code RuntimeException}
055   * to allow creating a CheckedFuture that throws both checked and unchecked exceptions.
056   */
057  // We might like @ForOverride here, but some subclasses invoke this from their get() methods.
058  protected abstract X mapException(Exception e);
059
060  /**
061   * {@inheritDoc}
062   *
063   * <p>This implementation calls {@link #get()} and maps that method's standard exceptions to
064   * instances of type {@code X} using {@link #mapException}.
065   *
066   * <p>In addition, if {@code get} throws an {@link InterruptedException}, this implementation will
067   * set the current thread's interrupt status before calling {@code mapException}.
068   *
069   * @throws X if {@link #get()} throws an {@link InterruptedException}, {@link
070   *     CancellationException}, or {@link ExecutionException}
071   */
072  @CanIgnoreReturnValue
073  @Override
074  public V checkedGet() throws X {
075    try {
076      return get();
077    } catch (InterruptedException e) {
078      Thread.currentThread().interrupt();
079      throw mapException(e);
080    } catch (CancellationException e) {
081      throw mapException(e);
082    } catch (ExecutionException e) {
083      throw mapException(e);
084    }
085  }
086
087  /**
088   * {@inheritDoc}
089   *
090   * <p>This implementation calls {@link #get(long, TimeUnit)} and maps that method's standard
091   * exceptions (excluding {@link TimeoutException}, which is propagated) to instances of type
092   * {@code X} using {@link #mapException}.
093   *
094   * <p>In addition, if {@code get} throws an {@link InterruptedException}, this implementation will
095   * set the current thread's interrupt status before calling {@code mapException}.
096   *
097   * @throws X if {@link #get()} throws an {@link InterruptedException}, {@link
098   *     CancellationException}, or {@link ExecutionException}
099   */
100  @CanIgnoreReturnValue
101  @Override
102  public V checkedGet(long timeout, TimeUnit unit) throws TimeoutException, X {
103    try {
104      return get(timeout, unit);
105    } catch (InterruptedException e) {
106      Thread.currentThread().interrupt();
107      throw mapException(e);
108    } catch (CancellationException e) {
109      throw mapException(e);
110    } catch (ExecutionException e) {
111      throw mapException(e);
112    }
113  }
114}