316 lines
11 KiB
Java
316 lines
11 KiB
Java
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* This file is available under and governed by the GNU General Public
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* License version 2 only, as published by the Free Software Foundation.
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* However, the following notice accompanied the original version of this
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* file:
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*
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* Written by Doug Lea with assistance from members of JCP JSR-166
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* Expert Group and released to the public domain, as explained at
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* http://creativecommons.org/publicdomain/zero/1.0/
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*/
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package java.util.concurrent;
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import static java.util.concurrent.TimeUnit.NANOSECONDS;
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import java.util.ArrayList;
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import java.util.Collection;
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import java.util.Iterator;
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import java.util.List;
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/**
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* Provides default implementations of {@link ExecutorService}
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* execution methods. This class implements the {@code submit},
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* {@code invokeAny} and {@code invokeAll} methods using a
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* {@link RunnableFuture} returned by {@code newTaskFor}, which defaults
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* to the {@link FutureTask} class provided in this package. For example,
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* the implementation of {@code submit(Runnable)} creates an
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* associated {@code RunnableFuture} that is executed and
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* returned. Subclasses may override the {@code newTaskFor} methods
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* to return {@code RunnableFuture} implementations other than
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* {@code FutureTask}.
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*
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* <p><b>Extension example.</b> Here is a sketch of a class
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* that customizes {@link ThreadPoolExecutor} to use
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* a {@code CustomTask} class instead of the default {@code FutureTask}:
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* <pre> {@code
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* public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
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*
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* static class CustomTask<V> implements RunnableFuture<V> { ... }
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*
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* protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
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* return new CustomTask<V>(c);
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* }
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* protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
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* return new CustomTask<V>(r, v);
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* }
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* // ... add constructors, etc.
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* }}</pre>
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*
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* @since 1.5
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* @author Doug Lea
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*/
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public abstract class AbstractExecutorService implements ExecutorService {
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/**
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* Constructor for subclasses to call.
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*/
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public AbstractExecutorService() {}
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/**
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* Returns a {@code RunnableFuture} for the given runnable and default
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* value.
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*
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* @param runnable the runnable task being wrapped
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* @param value the default value for the returned future
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* @param <T> the type of the given value
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* @return a {@code RunnableFuture} which, when run, will run the
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* underlying runnable and which, as a {@code Future}, will yield
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* the given value as its result and provide for cancellation of
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* the underlying task
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* @since 1.6
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*/
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protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
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return new FutureTask<T>(runnable, value);
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}
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/**
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* Returns a {@code RunnableFuture} for the given callable task.
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*
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* @param callable the callable task being wrapped
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* @param <T> the type of the callable's result
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* @return a {@code RunnableFuture} which, when run, will call the
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* underlying callable and which, as a {@code Future}, will yield
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* the callable's result as its result and provide for
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* cancellation of the underlying task
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* @since 1.6
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*/
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protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
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return new FutureTask<T>(callable);
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}
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/**
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* @throws RejectedExecutionException {@inheritDoc}
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* @throws NullPointerException {@inheritDoc}
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*/
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public Future<?> submit(Runnable task) {
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if (task == null) throw new NullPointerException();
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RunnableFuture<Void> ftask = newTaskFor(task, null);
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execute(ftask);
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return ftask;
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}
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/**
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* @throws RejectedExecutionException {@inheritDoc}
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* @throws NullPointerException {@inheritDoc}
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*/
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public <T> Future<T> submit(Runnable task, T result) {
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if (task == null) throw new NullPointerException();
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RunnableFuture<T> ftask = newTaskFor(task, result);
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execute(ftask);
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return ftask;
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}
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/**
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* @throws RejectedExecutionException {@inheritDoc}
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* @throws NullPointerException {@inheritDoc}
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*/
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public <T> Future<T> submit(Callable<T> task) {
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if (task == null) throw new NullPointerException();
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RunnableFuture<T> ftask = newTaskFor(task);
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execute(ftask);
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return ftask;
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}
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/**
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* the main mechanics of invokeAny.
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*/
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private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
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boolean timed, long nanos)
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throws InterruptedException, ExecutionException, TimeoutException {
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if (tasks == null)
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throw new NullPointerException();
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int ntasks = tasks.size();
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if (ntasks == 0)
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throw new IllegalArgumentException();
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ArrayList<Future<T>> futures = new ArrayList<>(ntasks);
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ExecutorCompletionService<T> ecs =
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new ExecutorCompletionService<T>(this);
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// For efficiency, especially in executors with limited
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// parallelism, check to see if previously submitted tasks are
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// done before submitting more of them. This interleaving
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// plus the exception mechanics account for messiness of main
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// loop.
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try {
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// Record exceptions so that if we fail to obtain any
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// result, we can throw the last exception we got.
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ExecutionException ee = null;
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final long deadline = timed ? System.nanoTime() + nanos : 0L;
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Iterator<? extends Callable<T>> it = tasks.iterator();
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// Start one task for sure; the rest incrementally
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futures.add(ecs.submit(it.next()));
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--ntasks;
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int active = 1;
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for (;;) {
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Future<T> f = ecs.poll();
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if (f == null) {
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if (ntasks > 0) {
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--ntasks;
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futures.add(ecs.submit(it.next()));
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++active;
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}
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else if (active == 0)
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break;
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else if (timed) {
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f = ecs.poll(nanos, NANOSECONDS);
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if (f == null)
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throw new TimeoutException();
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nanos = deadline - System.nanoTime();
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}
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else
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f = ecs.take();
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}
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if (f != null) {
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--active;
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try {
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return f.get();
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} catch (ExecutionException eex) {
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ee = eex;
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} catch (RuntimeException rex) {
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ee = new ExecutionException(rex);
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}
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}
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}
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if (ee == null)
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ee = new ExecutionException();
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throw ee;
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} finally {
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cancelAll(futures);
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}
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}
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public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
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throws InterruptedException, ExecutionException {
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try {
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return doInvokeAny(tasks, false, 0);
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} catch (TimeoutException cannotHappen) {
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assert false;
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return null;
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}
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}
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public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
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long timeout, TimeUnit unit)
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throws InterruptedException, ExecutionException, TimeoutException {
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return doInvokeAny(tasks, true, unit.toNanos(timeout));
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}
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public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
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throws InterruptedException {
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if (tasks == null)
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throw new NullPointerException();
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ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
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try {
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for (Callable<T> t : tasks) {
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RunnableFuture<T> f = newTaskFor(t);
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futures.add(f);
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execute(f);
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}
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for (int i = 0, size = futures.size(); i < size; i++) {
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Future<T> f = futures.get(i);
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if (!f.isDone()) {
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try { f.get(); }
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catch (CancellationException | ExecutionException ignore) {}
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}
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}
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return futures;
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} catch (Throwable t) {
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cancelAll(futures);
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throw t;
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}
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}
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public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
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long timeout, TimeUnit unit)
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throws InterruptedException {
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if (tasks == null)
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throw new NullPointerException();
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final long nanos = unit.toNanos(timeout);
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final long deadline = System.nanoTime() + nanos;
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ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
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int j = 0;
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timedOut: try {
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for (Callable<T> t : tasks)
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futures.add(newTaskFor(t));
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final int size = futures.size();
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// Interleave time checks and calls to execute in case
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// executor doesn't have any/much parallelism.
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for (int i = 0; i < size; i++) {
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if (((i == 0) ? nanos : deadline - System.nanoTime()) <= 0L)
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break timedOut;
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execute((Runnable)futures.get(i));
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}
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for (; j < size; j++) {
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Future<T> f = futures.get(j);
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if (!f.isDone()) {
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try { f.get(deadline - System.nanoTime(), NANOSECONDS); }
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catch (CancellationException | ExecutionException ignore) {}
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catch (TimeoutException timedOut) {
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break timedOut;
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}
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}
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}
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return futures;
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} catch (Throwable t) {
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cancelAll(futures);
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throw t;
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}
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// Timed out before all the tasks could be completed; cancel remaining
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cancelAll(futures, j);
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return futures;
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}
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private static <T> void cancelAll(ArrayList<Future<T>> futures) {
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cancelAll(futures, 0);
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}
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/** Cancels all futures with index at least j. */
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private static <T> void cancelAll(ArrayList<Future<T>> futures, int j) {
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for (int size = futures.size(); j < size; j++)
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futures.get(j).cancel(true);
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}
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}
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