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/*
 * Copyright (C) 2011 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.util.concurrent;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.base.Throwables;
import com.google.common.collect.ImmutableList;

import java.util.Collection;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

/**
 * An abstract {@code ExecutorService} that allows subclasses to
 * {@linkplain #wrapTask(Callable) wrap} tasks before they are submitted
 * to the underlying executor.
 *
 * 
Note that task wrapping may occur even if the task is never executed.
 *
 * 
For delegation without task-wrapping, see
 * {@link ForwardingExecutorService}.
 *
 * @author Chris Nokleberg
 */
abstract class WrappingExecutorService implements ExecutorService {
  private final ExecutorService delegate;

  protected WrappingExecutorService(ExecutorService delegate) {
    this.delegate = checkNotNull(delegate);
  }

  /**
   * Wraps a task  before it is submitted to the underlying Executor.
   * Though specified in terms of Callable, this method is also applied to
   * Runnable tasks.
   */
  protected abstract  Callable wrapTask(Callable callable);

  /**
   * Wraps a task before it is submitted to the underlying Executor.  This
   * delegates to {@link #wrapTask(Callable)} by default, but should be
   * overridden if there is a better implementation for {@link Runnable
   * runnables}.
   */
  protected Runnable wrapTask(Runnable command) {
    final Callable wrapped = wrapTask(
        Executors.callable(command, null));
    return new Runnable() {
      @Override public void run() {
        try {
          wrapped.call();
        } catch (Exception e) {
          Throwables.propagate(e);
        }
      }
    };
  }

  /**
   * Wraps a collection of tasks.
   *
   * @throws NullPointerException if any element of {@code tasks} is null
   */
  private final  ImmutableList> wrapTasks(
      Collection> tasks) {
    ImmutableList.Builder> builder = ImmutableList.builder();
    for (Callable task : tasks) {
      builder.add(wrapTask(task));
    }
    return builder.build();
  }

  // These methods wrap before delegating.
  @Override
  public final void execute(Runnable command) {
    delegate.execute(wrapTask(command));
  }

  @Override
  public final  Future submit(Callable task) {
    return delegate.submit(wrapTask(checkNotNull(task)));
  }

  @Override
  public final Future submit(Runnable task) {
    return delegate.submit(wrapTask(task));
  }

  @Override
  public final  Future submit(Runnable task, T result) {
    return delegate.submit(wrapTask(task), result);
  }

  @Override
  public final  List> invokeAll(
      Collection> tasks) throws InterruptedException {
    return delegate.invokeAll(wrapTasks(tasks));
  }

  @Override
  public final  List> invokeAll(
      Collection> tasks, long timeout, TimeUnit unit)
      throws InterruptedException {
    return delegate.invokeAll(wrapTasks(tasks), timeout, unit);
  }

  @Override
  public final  T invokeAny(Collection> tasks)
      throws InterruptedException, ExecutionException {
    return delegate.invokeAny(wrapTasks(tasks));
  }

  @Override
  public final  T invokeAny(
      Collection> tasks, long timeout, TimeUnit unit)
      throws InterruptedException, ExecutionException, TimeoutException {
    return delegate.invokeAny(wrapTasks(tasks), timeout, unit);
  }

  // The remaining methods just delegate.

  @Override
  public final void shutdown() {
    delegate.shutdown();
  }

  @Override
  public final List shutdownNow() {
    return delegate.shutdownNow();
  }

  @Override
  public final boolean isShutdown() {
    return delegate.isShutdown();
  }

  @Override
  public final boolean isTerminated() {
    return delegate.isTerminated();
  }

  @Override
  public final boolean awaitTermination(long timeout, TimeUnit unit)
      throws InterruptedException {
    return delegate.awaitTermination(timeout, unit);
  }
}
    

    

    
            
    
            







    
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