    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
    017    package com.google.common.util.concurrent;
    018
    019    import com.google.common.annotations.Beta;
    020
    021    import java.util.concurrent.CancellationException;
    022    import java.util.concurrent.ExecutionException;
    023    import java.util.concurrent.TimeUnit;
    024    import 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
    034    public 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    }