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    }