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.Executor;
024import java.util.concurrent.TimeUnit;
025import java.util.concurrent.TimeoutException;
026
027/**
028 * A delegating wrapper around a {@link ListenableFuture} that adds support for
029 * the {@link #checkedGet()} and {@link #checkedGet(long, TimeUnit)} methods.
030 *
031 * @author Sven Mawson
032 * @since 1
033 */
034@Beta
035public abstract class AbstractCheckedFuture<V, X extends Exception>
036    implements CheckedFuture<V, X> {
037
038  /** The delegate, used to pass along all our methods. */
039  protected final ListenableFuture<V> delegate;
040
041  /**
042   * Constructs an {@code AbstractCheckedFuture} that wraps a delegate.
043   */
044  protected AbstractCheckedFuture(ListenableFuture<V> delegate) {
045    this.delegate = delegate;
046  }
047
048  /**
049   * Translates from an {@link InterruptedException},
050   * {@link CancellationException} or {@link ExecutionException} thrown by
051   * {@code get} to an exception of type {@code X} to be thrown by
052   * {@code checkedGet}. Subclasses must implement this method.
053   *
054   * <p>If {@code e} is an {@code InterruptedException}, the calling
055   * {@code checkedGet} method has already restored the interrupt after catching
056   * the exception. If an implementation of {@link #mapException(Exception)}
057   * wishes to swallow the interrupt, it can do so by calling
058   * {@link Thread#interrupted()}.
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
118  // Delegate methods for methods defined in the ListenableFuture interface.
119
120  @Override
121  public boolean cancel(boolean mayInterruptIfRunning) {
122    return delegate.cancel(mayInterruptIfRunning);
123  }
124
125  @Override
126  public boolean isCancelled() {
127    return delegate.isCancelled();
128  }
129
130  @Override
131  public boolean isDone() {
132    return delegate.isDone();
133  }
134
135  @Override
136  public V get() throws InterruptedException, ExecutionException {
137    return delegate.get();
138  }
139
140  @Override
141  public V get(long timeout, TimeUnit unit) throws InterruptedException,
142      ExecutionException, TimeoutException {
143    return delegate.get(timeout, unit);
144  }
145
146  @Override
147  public void addListener(Runnable listener, Executor exec) {
148    delegate.addListener(listener, exec);
149  }
150}