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      1 /*
      2  * Copyright (C) 2008 The Guava Authors
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  * http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.google.common.util.concurrent;
     18 
     19 import com.google.common.annotations.Beta;
     20 
     21 import java.util.concurrent.CancellationException;
     22 import java.util.concurrent.ExecutionException;
     23 import java.util.concurrent.TimeUnit;
     24 import java.util.concurrent.TimeoutException;
     25 
     26 /**
     27  * A delegating wrapper around a {@link ListenableFuture} that adds support for
     28  * the {@link #checkedGet()} and {@link #checkedGet(long, TimeUnit)} methods.
     29  *
     30  * @author Sven Mawson
     31  * @since 1.0
     32  */
     33 @Beta
     34 public abstract class AbstractCheckedFuture<V, X extends Exception>
     35     extends ForwardingListenableFuture.SimpleForwardingListenableFuture<V>
     36     implements CheckedFuture<V, X> {
     37   /**
     38    * Constructs an {@code AbstractCheckedFuture} that wraps a delegate.
     39    */
     40   protected AbstractCheckedFuture(ListenableFuture<V> delegate) {
     41     super(delegate);
     42   }
     43 
     44   /**
     45    * Translates from an {@link InterruptedException},
     46    * {@link CancellationException} or {@link ExecutionException} thrown by
     47    * {@code get} to an exception of type {@code X} to be thrown by
     48    * {@code checkedGet}. Subclasses must implement this method.
     49    *
     50    * <p>If {@code e} is an {@code InterruptedException}, the calling
     51    * {@code checkedGet} method has already restored the interrupt after catching
     52    * the exception. If an implementation of {@link #mapException(Exception)}
     53    * wishes to swallow the interrupt, it can do so by calling
     54    * {@link Thread#interrupted()}.
     55    *
     56    * <p>Subclasses may choose to throw, rather than return, a subclass of
     57    * {@code RuntimeException} to allow creating a CheckedFuture that throws
     58    * both checked and unchecked exceptions.
     59    */
     60   protected abstract X mapException(Exception e);
     61 
     62   /**
     63    * {@inheritDoc}
     64    *
     65    * <p>This implementation calls {@link #get()} and maps that method's standard
     66    * exceptions to instances of type {@code X} using {@link #mapException}.
     67    *
     68    * <p>In addition, if {@code get} throws an {@link InterruptedException}, this
     69    * implementation will set the current thread's interrupt status before
     70    * calling {@code mapException}.
     71    *
     72    * @throws X if {@link #get()} throws an {@link InterruptedException},
     73    *         {@link CancellationException}, or {@link ExecutionException}
     74    */
     75   @Override
     76   public V checkedGet() throws X {
     77     try {
     78       return get();
     79     } catch (InterruptedException e) {
     80       Thread.currentThread().interrupt();
     81       throw mapException(e);
     82     } catch (CancellationException e) {
     83       throw mapException(e);
     84     } catch (ExecutionException e) {
     85       throw mapException(e);
     86     }
     87   }
     88 
     89   /**
     90    * {@inheritDoc}
     91    *
     92    * <p>This implementation calls {@link #get(long, TimeUnit)} and maps that
     93    * method's standard exceptions (excluding {@link TimeoutException}, which is
     94    * propagated) to instances of type {@code X} using {@link #mapException}.
     95    *
     96    * <p>In addition, if {@code get} throws an {@link InterruptedException}, this
     97    * implementation will set the current thread's interrupt status before
     98    * calling {@code mapException}.
     99    *
    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