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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 static com.google.common.base.Throwables.throwIfUnchecked;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.collect.ImmutableList;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
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 */ @CanIgnoreReturnValue // TODO(cpovirk): Consider being more strict. @GwtIncompatible abstract class WrappingExecutorService implements ExecutorService { private final ExecutorService delegate; protected WrappingExecutorService(ExecutorService delegate) { this.delegate = checkNotNull(delegate); } /** * Wraps a {@code Callable} for submission to the underlying executor. This method is also applied * to any {@code Runnable} passed to the default implementation of {@link #wrapTask(Runnable)}. */ protected abstract Callable wrapTask(Callable callable); /** * Wraps a {@code Runnable} for submission to the underlying executor. The default implementation * delegates to {@link #wrapTask(Callable)}. */ 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) { throwIfUnchecked(e); throw new RuntimeException(e); } } }; } /** * Wraps a collection of tasks. * * @throws NullPointerException if any element of {@code tasks} is null */ private 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); } }