1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25 /*
26 * This file is available under and governed by the GNU General Public
27 * License version 2 only, as published by the Free Software Foundation.
28 * However, the following notice accompanied the original version of this
29 * file:
30 *
31 * Written by Doug Lea with assistance from members of JCP JSR-166
32 * Expert Group and released to the public domain, as explained at
33 * http://creativecommons.org/publicdomain/zero/1.0/
34 */
35
36 package java.util.concurrent;
37
38 import static java.lang.ref.Reference.reachabilityFence;
39 import java.lang.ref.Cleaner.Cleanable;
40 import java.security.AccessControlContext;
41 import java.security.AccessControlException;
42 import java.security.AccessController;
43 import java.security.PrivilegedAction;
44 import java.security.PrivilegedActionException;
45 import java.security.PrivilegedExceptionAction;
46 import java.util.Collection;
47 import java.util.List;
48 import java.util.concurrent.atomic.AtomicInteger;
49 import jdk.internal.ref.CleanerFactory;
50 import sun.security.util.SecurityConstants;
51
52 /**
53 * Factory and utility methods for {@link Executor}, {@link
54 * ExecutorService}, {@link ScheduledExecutorService}, {@link
55 * ThreadFactory}, and {@link Callable} classes defined in this
56 * package. This class supports the following kinds of methods:
57 *
58 * <ul>
59 * <li>Methods that create and return an {@link ExecutorService}
60 * set up with commonly useful configuration settings.
61 * <li>Methods that create and return a {@link ScheduledExecutorService}
62 * set up with commonly useful configuration settings.
63 * <li>Methods that create and return a "wrapped" ExecutorService, that
64 * disables reconfiguration by making implementation-specific methods
65 * inaccessible.
66 * <li>Methods that create and return a {@link ThreadFactory}
67 * that sets newly created threads to a known state.
68 * <li>Methods that create and return a {@link Callable}
69 * out of other closure-like forms, so they can be used
70 * in execution methods requiring {@code Callable}.
71 * </ul>
72 *
73 * @since 1.5
74 * @author Doug Lea
75 */
76 public class Executors {
77
78 /**
79 * Creates a thread pool that reuses a fixed number of threads
80 * operating off a shared unbounded queue. At any point, at most
81 * {@code nThreads} threads will be active processing tasks.
82 * If additional tasks are submitted when all threads are active,
83 * they will wait in the queue until a thread is available.
84 * If any thread terminates due to a failure during execution
85 * prior to shutdown, a new one will take its place if needed to
86 * execute subsequent tasks. The threads in the pool will exist
87 * until it is explicitly {@link ExecutorService#shutdown shutdown}.
88 *
89 * @param nThreads the number of threads in the pool
90 * @return the newly created thread pool
91 * @throws IllegalArgumentException if {@code nThreads <= 0}
92 */
93 public static ExecutorService newFixedThreadPool(int nThreads) {
94 return new ThreadPoolExecutor(nThreads, nThreads,
95 0L, TimeUnit.MILLISECONDS,
96 new LinkedBlockingQueue<Runnable>());
97 }
98
99 /**
100 * Creates a thread pool that maintains enough threads to support
101 * the given parallelism level, and may use multiple queues to
102 * reduce contention. The parallelism level corresponds to the
103 * maximum number of threads actively engaged in, or available to
104 * engage in, task processing. The actual number of threads may
105 * grow and shrink dynamically. A work-stealing pool makes no
106 * guarantees about the order in which submitted tasks are
107 * executed.
108 *
109 * @param parallelism the targeted parallelism level
110 * @return the newly created thread pool
111 * @throws IllegalArgumentException if {@code parallelism <= 0}
112 * @since 1.8
113 */
114 public static ExecutorService newWorkStealingPool(int parallelism) {
115 return new ForkJoinPool
116 (parallelism,
117 ForkJoinPool.defaultForkJoinWorkerThreadFactory,
118 null, true);
119 }
120
121 /**
122 * Creates a work-stealing thread pool using the number of
123 * {@linkplain Runtime#availableProcessors available processors}
124 * as its target parallelism level.
125 *
126 * @return the newly created thread pool
127 * @see #newWorkStealingPool(int)
128 * @since 1.8
129 */
130 public static ExecutorService newWorkStealingPool() {
131 return new ForkJoinPool
132 (Runtime.getRuntime().availableProcessors(),
133 ForkJoinPool.defaultForkJoinWorkerThreadFactory,
134 null, true);
135 }
136
137 /**
138 * Creates a thread pool that reuses a fixed number of threads
139 * operating off a shared unbounded queue, using the provided
140 * ThreadFactory to create new threads when needed. At any point,
141 * at most {@code nThreads} threads will be active processing
142 * tasks. If additional tasks are submitted when all threads are
143 * active, they will wait in the queue until a thread is
144 * available. If any thread terminates due to a failure during
145 * execution prior to shutdown, a new one will take its place if
146 * needed to execute subsequent tasks. The threads in the pool will
147 * exist until it is explicitly {@link ExecutorService#shutdown
148 * shutdown}.
149 *
150 * @param nThreads the number of threads in the pool
151 * @param threadFactory the factory to use when creating new threads
152 * @return the newly created thread pool
153 * @throws NullPointerException if threadFactory is null
154 * @throws IllegalArgumentException if {@code nThreads <= 0}
155 */
156 public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory) {
157 return new ThreadPoolExecutor(nThreads, nThreads,
158 0L, TimeUnit.MILLISECONDS,
159 new LinkedBlockingQueue<Runnable>(),
160 threadFactory);
161 }
162
163 /**
164 * Creates an Executor that uses a single worker thread operating
165 * off an unbounded queue. (Note however that if this single
166 * thread terminates due to a failure during execution prior to
167 * shutdown, a new one will take its place if needed to execute
168 * subsequent tasks.) Tasks are guaranteed to execute
169 * sequentially, and no more than one task will be active at any
170 * given time. Unlike the otherwise equivalent
171 * {@code newFixedThreadPool(1)} the returned executor is
172 * guaranteed not to be reconfigurable to use additional threads.
173 *
174 * @return the newly created single-threaded Executor
175 */
176 public static ExecutorService newSingleThreadExecutor() {
177 return newSingleThreadExecutor(defaultThreadFactory());
178 }
179
180 /**
181 * Creates an Executor that uses a single worker thread operating
182 * off an unbounded queue, and uses the provided ThreadFactory to
183 * create a new thread when needed. Unlike the otherwise
184 * equivalent {@code newFixedThreadPool(1, threadFactory)} the
185 * returned executor is guaranteed not to be reconfigurable to use
186 * additional threads.
187 *
188 * @param threadFactory the factory to use when creating new threads
189 * @return the newly created single-threaded Executor
190 * @throws NullPointerException if threadFactory is null
191 */
192 public static ExecutorService newSingleThreadExecutor(ThreadFactory threadFactory) {
193 return new AutoShutdownDelegatedExecutorService
194 (new ThreadPoolExecutor(1, 1,
195 0L, TimeUnit.MILLISECONDS,
196 new LinkedBlockingQueue<Runnable>(),
197 threadFactory));
198 }
199
200 /**
201 * Creates a thread pool that creates new threads as needed, but
202 * will reuse previously constructed threads when they are
203 * available. These pools will typically improve the performance
204 * of programs that execute many short-lived asynchronous tasks.
205 * Calls to {@code execute} will reuse previously constructed
206 * threads if available. If no existing thread is available, a new
207 * thread will be created and added to the pool. Threads that have
208 * not been used for sixty seconds are terminated and removed from
209 * the cache. Thus, a pool that remains idle for long enough will
210 * not consume any resources. Note that pools with similar
211 * properties but different details (for example, timeout parameters)
212 * may be created using {@link ThreadPoolExecutor} constructors.
213 *
214 * @return the newly created thread pool
215 */
216 public static ExecutorService newCachedThreadPool() {
217 return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
218 60L, TimeUnit.SECONDS,
219 new SynchronousQueue<Runnable>());
220 }
221
222 /**
223 * Creates a thread pool that creates new threads as needed, but
224 * will reuse previously constructed threads when they are
225 * available, and uses the provided
226 * ThreadFactory to create new threads when needed.
227 *
228 * @param threadFactory the factory to use when creating new threads
229 * @return the newly created thread pool
230 * @throws NullPointerException if threadFactory is null
231 */
232 public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory) {
233 return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
234 60L, TimeUnit.SECONDS,
235 new SynchronousQueue<Runnable>(),
236 threadFactory);
237 }
238
239 /**
240 * Creates an Executor that starts a new Thread for each task.
241 * The number of threads created by the Executor is unbounded.
242 *
243 * <p> Invoking {@link Future#cancel(boolean) cancel(true)} on a {@link
244 * Future Future} representing the pending result of a task submitted to
245 * the Executor will {@link Thread#interrupt() interrupt} the thread
246 * executing the task.
247 *
248 * @param threadFactory the factory to use when creating new threads
249 * @return a new executor that creates a new Thread for each task
250 * @throws NullPointerException if threadFactory is null
251 * @since 21
252 */
253 public static ExecutorService newThreadPerTaskExecutor(ThreadFactory threadFactory) {
254 return ThreadPerTaskExecutor.create(threadFactory);
255 }
256
257 /**
258 * Creates an Executor that starts a new virtual Thread for each task.
259 * The number of threads created by the Executor is unbounded.
260 *
261 * <p> This method is equivalent to invoking
262 * {@link #newThreadPerTaskExecutor(ThreadFactory)} with a thread factory
263 * that creates virtual threads.
264 *
265 * @return a new executor that creates a new virtual Thread for each task
266 * @since 21
267 */
268 public static ExecutorService newVirtualThreadPerTaskExecutor() {
269 ThreadFactory factory = Thread.ofVirtual().factory();
270 return newThreadPerTaskExecutor(factory);
271 }
272
273 /**
274 * Creates a single-threaded executor that can schedule commands
275 * to run after a given delay, or to execute periodically.
276 * (Note however that if this single
277 * thread terminates due to a failure during execution prior to
278 * shutdown, a new one will take its place if needed to execute
279 * subsequent tasks.) Tasks are guaranteed to execute
280 * sequentially, and no more than one task will be active at any
281 * given time. Unlike the otherwise equivalent
282 * {@code newScheduledThreadPool(1)} the returned executor is
283 * guaranteed not to be reconfigurable to use additional threads.
284 *
285 * @return the newly created scheduled executor
286 */
287 public static ScheduledExecutorService newSingleThreadScheduledExecutor() {
288 return new DelegatedScheduledExecutorService
289 (new ScheduledThreadPoolExecutor(1));
290 }
291
292 /**
293 * Creates a single-threaded executor that can schedule commands
294 * to run after a given delay, or to execute periodically. (Note
295 * however that if this single thread terminates due to a failure
296 * during execution prior to shutdown, a new one will take its
297 * place if needed to execute subsequent tasks.) Tasks are
298 * guaranteed to execute sequentially, and no more than one task
299 * will be active at any given time. Unlike the otherwise
300 * equivalent {@code newScheduledThreadPool(1, threadFactory)}
301 * the returned executor is guaranteed not to be reconfigurable to
302 * use additional threads.
303 *
304 * @param threadFactory the factory to use when creating new threads
305 * @return the newly created scheduled executor
306 * @throws NullPointerException if threadFactory is null
307 */
308 public static ScheduledExecutorService newSingleThreadScheduledExecutor(ThreadFactory threadFactory) {
309 return new DelegatedScheduledExecutorService
310 (new ScheduledThreadPoolExecutor(1, threadFactory));
311 }
312
313 /**
314 * Creates a thread pool that can schedule commands to run after a
315 * given delay, or to execute periodically.
316 * @param corePoolSize the number of threads to keep in the pool,
317 * even if they are idle
318 * @return the newly created scheduled thread pool
319 * @throws IllegalArgumentException if {@code corePoolSize < 0}
320 */
321 public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
322 return new ScheduledThreadPoolExecutor(corePoolSize);
323 }
324
325 /**
326 * Creates a thread pool that can schedule commands to run after a
327 * given delay, or to execute periodically.
328 * @param corePoolSize the number of threads to keep in the pool,
329 * even if they are idle
330 * @param threadFactory the factory to use when the executor
331 * creates a new thread
332 * @return the newly created scheduled thread pool
333 * @throws IllegalArgumentException if {@code corePoolSize < 0}
334 * @throws NullPointerException if threadFactory is null
335 */
336 public static ScheduledExecutorService newScheduledThreadPool(
337 int corePoolSize, ThreadFactory threadFactory) {
338 return new ScheduledThreadPoolExecutor(corePoolSize, threadFactory);
339 }
340
341 /**
342 * Returns an object that delegates all defined {@link
343 * ExecutorService} methods to the given executor, but not any
344 * other methods that might otherwise be accessible using
345 * casts. This provides a way to safely "freeze" configuration and
346 * disallow tuning of a given concrete implementation.
347 * @param executor the underlying implementation
348 * @return an {@code ExecutorService} instance
349 * @throws NullPointerException if executor null
350 */
351 public static ExecutorService unconfigurableExecutorService(ExecutorService executor) {
352 if (executor == null)
353 throw new NullPointerException();
354 return new DelegatedExecutorService(executor);
355 }
356
357 /**
358 * Returns an object that delegates all defined {@link
359 * ScheduledExecutorService} methods to the given executor, but
360 * not any other methods that might otherwise be accessible using
361 * casts. This provides a way to safely "freeze" configuration and
362 * disallow tuning of a given concrete implementation.
363 * @param executor the underlying implementation
364 * @return a {@code ScheduledExecutorService} instance
365 * @throws NullPointerException if executor null
366 */
367 public static ScheduledExecutorService unconfigurableScheduledExecutorService(ScheduledExecutorService executor) {
368 if (executor == null)
369 throw new NullPointerException();
370 return new DelegatedScheduledExecutorService(executor);
371 }
372
373 /**
374 * Returns a default thread factory used to create new threads.
375 * This factory creates all new threads used by an Executor in the
376 * same {@link ThreadGroup}. If there is a {@link
377 * java.lang.SecurityManager}, it uses the group of {@link
378 * System#getSecurityManager}, else the group of the thread
379 * invoking this {@code defaultThreadFactory} method. Each new
380 * thread is created as a non-daemon thread with priority set to
381 * the smaller of {@code Thread.NORM_PRIORITY} and the maximum
382 * priority permitted in the thread group. New threads have names
383 * accessible via {@link Thread#getName} of
384 * <em>pool-N-thread-M</em>, where <em>N</em> is the sequence
385 * number of this factory, and <em>M</em> is the sequence number
386 * of the thread created by this factory.
387 * @return a thread factory
388 */
389 public static ThreadFactory defaultThreadFactory() {
390 return new DefaultThreadFactory();
391 }
392
393 /**
394 * Returns a thread factory used to create new threads that
395 * have the same permissions as the current thread.
396 * This factory creates threads with the same settings as {@link
397 * Executors#defaultThreadFactory}, additionally setting the
398 * AccessControlContext and contextClassLoader of new threads to
399 * be the same as the thread invoking this
400 * {@code privilegedThreadFactory} method. A new
401 * {@code privilegedThreadFactory} can be created within an
402 * {@link AccessController#doPrivileged AccessController.doPrivileged}
403 * action setting the current thread's access control context to
404 * create threads with the selected permission settings holding
405 * within that action.
406 *
407 * <p>Note that while tasks running within such threads will have
408 * the same access control and class loader settings as the
409 * current thread, they need not have the same {@link
410 * java.lang.ThreadLocal} or {@link
411 * java.lang.InheritableThreadLocal} values. If necessary,
412 * particular values of thread locals can be set or reset before
413 * any task runs in {@link ThreadPoolExecutor} subclasses using
414 * {@link ThreadPoolExecutor#beforeExecute(Thread, Runnable)}.
415 * Also, if it is necessary to initialize worker threads to have
416 * the same InheritableThreadLocal settings as some other
417 * designated thread, you can create a custom ThreadFactory in
418 * which that thread waits for and services requests to create
419 * others that will inherit its values.
420 *
421 * @return a thread factory
422 * @throws AccessControlException if the current access control
423 * context does not have permission to both get and set context
424 * class loader
425 *
426 * @deprecated This method is only useful in conjunction with
427 * {@linkplain SecurityManager the Security Manager}, which is
428 * deprecated and subject to removal in a future release.
429 * Consequently, this method is also deprecated and subject to
430 * removal. There is no replacement for the Security Manager or this
431 * method.
432 */
433 @Deprecated(since="17", forRemoval=true)
434 public static ThreadFactory privilegedThreadFactory() {
435 return new PrivilegedThreadFactory();
436 }
437
438 /**
439 * Returns a {@link Callable} object that, when
440 * called, runs the given task and returns the given result. This
441 * can be useful when applying methods requiring a
442 * {@code Callable} to an otherwise resultless action.
443 * @param task the task to run
444 * @param result the result to return
445 * @param <T> the type of the result
446 * @return a callable object
447 * @throws NullPointerException if task null
448 */
449 public static <T> Callable<T> callable(Runnable task, T result) {
450 if (task == null)
451 throw new NullPointerException();
452 return new RunnableAdapter<T>(task, result);
453 }
454
455 /**
456 * Returns a {@link Callable} object that, when
457 * called, runs the given task and returns {@code null}.
458 * @param task the task to run
459 * @return a callable object
460 * @throws NullPointerException if task null
461 */
462 public static Callable<Object> callable(Runnable task) {
463 if (task == null)
464 throw new NullPointerException();
465 return new RunnableAdapter<Object>(task, null);
466 }
467
468 /**
469 * Returns a {@link Callable} object that, when
470 * called, runs the given privileged action and returns its result.
471 * @param action the privileged action to run
472 * @return a callable object
473 * @throws NullPointerException if action null
474 */
475 public static Callable<Object> callable(final PrivilegedAction<?> action) {
476 if (action == null)
477 throw new NullPointerException();
478 return new Callable<Object>() {
479 public Object call() { return action.run(); }};
480 }
481
482 /**
483 * Returns a {@link Callable} object that, when
484 * called, runs the given privileged exception action and returns
485 * its result.
486 * @param action the privileged exception action to run
487 * @return a callable object
488 * @throws NullPointerException if action null
489 */
490 public static Callable<Object> callable(final PrivilegedExceptionAction<?> action) {
491 if (action == null)
492 throw new NullPointerException();
493 return new Callable<Object>() {
494 public Object call() throws Exception { return action.run(); }};
495 }
496
497 /**
498 * Returns a {@link Callable} object that will, when called,
499 * execute the given {@code callable} under the current access
500 * control context. This method should normally be invoked within
501 * an {@link AccessController#doPrivileged AccessController.doPrivileged}
502 * action to create callables that will, if possible, execute
503 * under the selected permission settings holding within that
504 * action; or if not possible, throw an associated {@link
505 * AccessControlException}.
506 * @param callable the underlying task
507 * @param <T> the type of the callable's result
508 * @return a callable object
509 * @throws NullPointerException if callable null
510 *
511 * @deprecated This method is only useful in conjunction with
512 * {@linkplain SecurityManager the Security Manager}, which is
513 * deprecated and subject to removal in a future release.
514 * Consequently, this method is also deprecated and subject to
515 * removal. There is no replacement for the Security Manager or this
516 * method.
517 */
518 @Deprecated(since="17", forRemoval=true)
519 public static <T> Callable<T> privilegedCallable(Callable<T> callable) {
520 if (callable == null)
521 throw new NullPointerException();
522 return new PrivilegedCallable<T>(callable);
523 }
524
525 /**
526 * Returns a {@link Callable} object that will, when called,
527 * execute the given {@code callable} under the current access
528 * control context, with the current context class loader as the
529 * context class loader. This method should normally be invoked
530 * within an
531 * {@link AccessController#doPrivileged AccessController.doPrivileged}
532 * action to create callables that will, if possible, execute
533 * under the selected permission settings holding within that
534 * action; or if not possible, throw an associated {@link
535 * AccessControlException}.
536 *
537 * @param callable the underlying task
538 * @param <T> the type of the callable's result
539 * @return a callable object
540 * @throws NullPointerException if callable null
541 * @throws AccessControlException if the current access control
542 * context does not have permission to both set and get context
543 * class loader
544 *
545 * @deprecated This method is only useful in conjunction with
546 * {@linkplain SecurityManager the Security Manager}, which is
547 * deprecated and subject to removal in a future release.
548 * Consequently, this method is also deprecated and subject to
549 * removal. There is no replacement for the Security Manager or this
550 * method.
551 */
552 @Deprecated(since="17", forRemoval=true)
553 public static <T> Callable<T> privilegedCallableUsingCurrentClassLoader(Callable<T> callable) {
554 if (callable == null)
555 throw new NullPointerException();
556 return new PrivilegedCallableUsingCurrentClassLoader<T>(callable);
557 }
558
559 // Non-public classes supporting the public methods
560
561 /**
562 * A callable that runs given task and returns given result.
563 */
564 private static final class RunnableAdapter<T> implements Callable<T> {
565 private final Runnable task;
566 private final T result;
567 RunnableAdapter(Runnable task, T result) {
568 this.task = task;
569 this.result = result;
570 }
571 public T call() {
572 task.run();
573 return result;
574 }
575 public String toString() {
576 return super.toString() + "[Wrapped task = " + task + "]";
577 }
578 }
579
580 /**
581 * A callable that runs under established access control settings.
582 */
583 private static final class PrivilegedCallable<T> implements Callable<T> {
584 final Callable<T> task;
585 @SuppressWarnings("removal")
586 final AccessControlContext acc;
587
588 @SuppressWarnings("removal")
589 PrivilegedCallable(Callable<T> task) {
590 this.task = task;
591 this.acc = AccessController.getContext();
592 }
593
594 @SuppressWarnings("removal")
595 public T call() throws Exception {
596 try {
597 return AccessController.doPrivileged(
598 new PrivilegedExceptionAction<T>() {
599 public T run() throws Exception {
600 return task.call();
601 }
602 }, acc);
603 } catch (PrivilegedActionException e) {
604 throw e.getException();
605 }
606 }
607
608 public String toString() {
609 return super.toString() + "[Wrapped task = " + task + "]";
610 }
611 }
612
613 /**
614 * A callable that runs under established access control settings and
615 * current ClassLoader.
616 */
617 private static final class PrivilegedCallableUsingCurrentClassLoader<T>
618 implements Callable<T> {
619 final Callable<T> task;
620 @SuppressWarnings("removal")
621 final AccessControlContext acc;
622 final ClassLoader ccl;
623
624 @SuppressWarnings("removal")
625 PrivilegedCallableUsingCurrentClassLoader(Callable<T> task) {
626 SecurityManager sm = System.getSecurityManager();
627 if (sm != null) {
628 // Calls to getContextClassLoader from this class
629 // never trigger a security check, but we check
630 // whether our callers have this permission anyways.
631 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
632
633 // Whether setContextClassLoader turns out to be necessary
634 // or not, we fail fast if permission is not available.
635 sm.checkPermission(new RuntimePermission("setContextClassLoader"));
636 }
637 this.task = task;
638 this.acc = AccessController.getContext();
639 this.ccl = Thread.currentThread().getContextClassLoader();
640 }
641
642 @SuppressWarnings("removal")
643 public T call() throws Exception {
644 try {
645 return AccessController.doPrivileged(
646 new PrivilegedExceptionAction<T>() {
647 public T run() throws Exception {
648 Thread t = Thread.currentThread();
649 ClassLoader cl = t.getContextClassLoader();
650 if (ccl == cl) {
651 return task.call();
652 } else {
653 t.setContextClassLoader(ccl);
654 try {
655 return task.call();
656 } finally {
657 t.setContextClassLoader(cl);
658 }
659 }
660 }
661 }, acc);
662 } catch (PrivilegedActionException e) {
663 throw e.getException();
664 }
665 }
666
667 public String toString() {
668 return super.toString() + "[Wrapped task = " + task + "]";
669 }
670 }
671
672 /**
673 * The default thread factory.
674 */
675 private static class DefaultThreadFactory implements ThreadFactory {
676 private static final AtomicInteger poolNumber = new AtomicInteger(1);
677 private final ThreadGroup group;
678 private final AtomicInteger threadNumber = new AtomicInteger(1);
679 private final String namePrefix;
680
681 DefaultThreadFactory() {
682 @SuppressWarnings("removal")
683 SecurityManager s = System.getSecurityManager();
684 group = (s != null) ? s.getThreadGroup() :
685 Thread.currentThread().getThreadGroup();
686 namePrefix = "pool-" +
687 poolNumber.getAndIncrement() +
688 "-thread-";
689 }
690
691 public Thread newThread(Runnable r) {
692 Thread t = new Thread(group, r,
693 namePrefix + threadNumber.getAndIncrement(),
694 0);
695 if (t.isDaemon())
696 t.setDaemon(false);
697 if (t.getPriority() != Thread.NORM_PRIORITY)
698 t.setPriority(Thread.NORM_PRIORITY);
699 return t;
700 }
701 }
702
703 /**
704 * Thread factory capturing access control context and class loader.
705 */
706 private static class PrivilegedThreadFactory extends DefaultThreadFactory {
707 @SuppressWarnings("removal")
708 final AccessControlContext acc;
709 final ClassLoader ccl;
710
711 @SuppressWarnings("removal")
712 PrivilegedThreadFactory() {
713 super();
714 SecurityManager sm = System.getSecurityManager();
715 if (sm != null) {
716 // Calls to getContextClassLoader from this class
717 // never trigger a security check, but we check
718 // whether our callers have this permission anyways.
719 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
720
721 // Fail fast
722 sm.checkPermission(new RuntimePermission("setContextClassLoader"));
723 }
724 this.acc = AccessController.getContext();
725 this.ccl = Thread.currentThread().getContextClassLoader();
726 }
727
728 public Thread newThread(final Runnable r) {
729 return super.newThread(new Runnable() {
730 @SuppressWarnings("removal")
731 public void run() {
732 AccessController.doPrivileged(new PrivilegedAction<>() {
733 public Void run() {
734 Thread.currentThread().setContextClassLoader(ccl);
735 r.run();
736 return null;
737 }
738 }, acc);
739 }
740 });
741 }
742 }
743
744 /**
745 * A wrapper class that exposes only the ExecutorService methods
746 * of an ExecutorService implementation.
747 */
748 private static class DelegatedExecutorService
749 implements ExecutorService {
750 private final ExecutorService e;
751 DelegatedExecutorService(ExecutorService executor) { e = executor; }
752 public void execute(Runnable command) {
753 try {
754 e.execute(command);
755 } finally { reachabilityFence(this); }
756 }
757 public void shutdown() {
758 try {
759 e.shutdown();
760 } finally { reachabilityFence(this); }
761 }
762 public List<Runnable> shutdownNow() {
763 try {
764 return e.shutdownNow();
765 } finally { reachabilityFence(this); }
766 }
767 public boolean isShutdown() {
768 try {
769 return e.isShutdown();
770 } finally { reachabilityFence(this); }
771 }
772 public boolean isTerminated() {
773 try {
774 return e.isTerminated();
775 } finally { reachabilityFence(this); }
776 }
777 public boolean awaitTermination(long timeout, TimeUnit unit)
778 throws InterruptedException {
779 try {
780 return e.awaitTermination(timeout, unit);
781 } finally { reachabilityFence(this); }
782 }
783 public Future<?> submit(Runnable task) {
784 try {
785 return e.submit(task);
786 } finally { reachabilityFence(this); }
787 }
788 public <T> Future<T> submit(Callable<T> task) {
789 try {
790 return e.submit(task);
791 } finally { reachabilityFence(this); }
792 }
793 public <T> Future<T> submit(Runnable task, T result) {
794 try {
795 return e.submit(task, result);
796 } finally { reachabilityFence(this); }
797 }
798 public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
799 throws InterruptedException {
800 try {
801 return e.invokeAll(tasks);
802 } finally { reachabilityFence(this); }
803 }
804 public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
805 long timeout, TimeUnit unit)
806 throws InterruptedException {
807 try {
808 return e.invokeAll(tasks, timeout, unit);
809 } finally { reachabilityFence(this); }
810 }
811 public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
812 throws InterruptedException, ExecutionException {
813 try {
814 return e.invokeAny(tasks);
815 } finally { reachabilityFence(this); }
816 }
817 public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
818 long timeout, TimeUnit unit)
819 throws InterruptedException, ExecutionException, TimeoutException {
820 try {
821 return e.invokeAny(tasks, timeout, unit);
822 } finally { reachabilityFence(this); }
823 }
824 }
825
826 /**
827 * A DelegatedExecutorService that uses a Cleaner to shut down the underlying
828 * ExecutorService when the wrapper becomes phantom reachable.
829 */
830 private static class AutoShutdownDelegatedExecutorService
831 extends DelegatedExecutorService {
832 private final Cleanable cleanable;
833 AutoShutdownDelegatedExecutorService(ExecutorService executor) {
834 super(executor);
835 Runnable action = () -> {
836 if (!executor.isShutdown()) {
837 PrivilegedAction<Void> pa = () -> { executor.shutdown(); return null; };
838 @SuppressWarnings("removal")
839 var ignore = AccessController.doPrivileged(pa);
840 }
841 };
842 cleanable = CleanerFactory.cleaner().register(this, action);
843 }
844 @Override
845 public void shutdown() {
846 super.shutdown();
847 cleanable.clean(); // unregisters the cleanable
848 }
849 }
850
851 /**
852 * A wrapper class that exposes only the ScheduledExecutorService
853 * methods of a ScheduledExecutorService implementation.
854 */
855 private static class DelegatedScheduledExecutorService
856 extends DelegatedExecutorService
857 implements ScheduledExecutorService {
858 private final ScheduledExecutorService e;
859 DelegatedScheduledExecutorService(ScheduledExecutorService executor) {
860 super(executor);
861 e = executor;
862 }
863 public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
864 return e.schedule(command, delay, unit);
865 }
866 public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {
867 return e.schedule(callable, delay, unit);
868 }
869 public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
870 return e.scheduleAtFixedRate(command, initialDelay, period, unit);
871 }
872 public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
873 return e.scheduleWithFixedDelay(command, initialDelay, delay, unit);
874 }
875 }
876
877 /** Cannot instantiate. */
878 private Executors() {}
879 }