001/*
002 * Copyright (C) 2008 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;
020
021import java.util.concurrent.CancellationException;
022import java.util.concurrent.ExecutionException;
023import java.util.concurrent.TimeUnit;
024import java.util.concurrent.TimeoutException;
025
026/**
027 * A delegating wrapper around a {@link ListenableFuture} that adds support for
028 * the {@link #checkedGet()} and {@link #checkedGet(long, TimeUnit)} methods.
029 *
030 * @author Sven Mawson
031 * @since 1.0
032 */
033@Beta
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},
046   * {@link CancellationException} or {@link ExecutionException} thrown by
047   * {@code get} to an exception of type {@code X} to be thrown by
048   * {@code checkedGet}. Subclasses must implement this method.
049   *
050   * <p>If {@code e} is an {@code InterruptedException}, the calling
051   * {@code checkedGet} method has already restored the interrupt after catching
052   * the exception. If an implementation of {@link #mapException(Exception)}
053   * wishes to swallow the interrupt, it can do so by calling
054   * {@link Thread#interrupted()}.
055   *
056   * <p>Subclasses may choose to throw, rather than return, a subclass of
057   * {@code RuntimeException} to allow creating a CheckedFuture that throws
058   * both checked and unchecked exceptions.
059   */
060  protected abstract X mapException(Exception e);
061
062  /**
063   * {@inheritDoc}
064   *
065   * <p>This implementation calls {@link #get()} and maps that method's standard
066   * exceptions to instances of type {@code X} using {@link #mapException}.
067   *
068   * <p>In addition, if {@code get} throws an {@link InterruptedException}, this
069   * implementation will set the current thread's interrupt status before
070   * calling {@code mapException}.
071   *
072   * @throws X if {@link #get()} throws an {@link InterruptedException},
073   *         {@link CancellationException}, or {@link ExecutionException}
074   */
075  @Override
076  public V checkedGet() throws X {
077    try {
078      return get();
079    } catch (InterruptedException e) {
080      Thread.currentThread().interrupt();
081      throw mapException(e);
082    } catch (CancellationException e) {
083      throw mapException(e);
084    } catch (ExecutionException e) {
085      throw mapException(e);
086    }
087  }
088
089  /**
090   * {@inheritDoc}
091   *
092   * <p>This implementation calls {@link #get(long, TimeUnit)} and maps that
093   * method's standard exceptions (excluding {@link TimeoutException}, which is
094   * propagated) to instances of type {@code X} using {@link #mapException}.
095   *
096   * <p>In addition, if {@code get} throws an {@link InterruptedException}, this
097   * implementation will set the current thread's interrupt status before
098   * calling {@code mapException}.
099   *
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}