001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.lang3;
018
019import java.util.ArrayList;
020import java.util.Collection;
021import java.util.Collections;
022import java.util.List;
023
024/**
025 * <p>
026 * Helpers for {@code java.lang.Thread} and {@code java.lang.ThreadGroup}.
027 * </p>
028 * <p>
029 * #ThreadSafe#
030 * </p>
031 *
032 * @see java.lang.Thread
033 * @see java.lang.ThreadGroup
034 * @since 3.5
035 */
036public class ThreadUtils {
037
038    /**
039     * Return the active thread with the specified id if it belongs to the specified thread group.
040     *
041     * @param threadId The thread id
042     * @param threadGroup The thread group
043     * @return The thread which belongs to a specified thread group and the thread's id match the specified id.
044     * {@code null} is returned if no such thread exists
045     * @throws IllegalArgumentException if the specified id is zero or negative or the group is null
046     * @throws  SecurityException
047     *          if the current thread cannot access the system thread group
048     *
049     * @throws  SecurityException  if the current thread cannot modify
050     *          thread groups from this thread's thread group up to the system thread group
051     */
052    public static Thread findThreadById(final long threadId, final ThreadGroup threadGroup) {
053        Validate.isTrue(threadGroup != null, "The thread group must not be null");
054        final Thread thread = findThreadById(threadId);
055        if (thread != null && threadGroup.equals(thread.getThreadGroup())) {
056            return thread;
057        }
058        return null;
059    }
060
061    /**
062     * Return the active thread with the specified id if it belongs to a thread group with the specified group name.
063     *
064     * @param threadId The thread id
065     * @param threadGroupName The thread group name
066     * @return The threads which belongs to a thread group with the specified group name and the thread's id match the specified id.
067     * {@code null} is returned if no such thread exists
068     * @throws IllegalArgumentException if the specified id is zero or negative or the group name is null
069     * @throws  SecurityException
070     *          if the current thread cannot access the system thread group
071     *
072     * @throws  SecurityException  if the current thread cannot modify
073     *          thread groups from this thread's thread group up to the system thread group
074     */
075    public static Thread findThreadById(final long threadId, final String threadGroupName) {
076        Validate.isTrue(threadGroupName != null, "The thread group name must not be null");
077        final Thread thread = findThreadById(threadId);
078        if (thread != null && thread.getThreadGroup() != null && thread.getThreadGroup().getName().equals(threadGroupName)) {
079            return thread;
080        }
081        return null;
082    }
083
084    /**
085     * Return active threads with the specified name if they belong to a specified thread group.
086     *
087     * @param threadName The thread name
088     * @param threadGroup The thread group
089     * @return The threads which belongs to a thread group and the thread's name match the specified name,
090     * An empty collection is returned if no such thread exists. The collection returned is always unmodifiable.
091     * @throws IllegalArgumentException if the specified thread name or group is null
092     * @throws  SecurityException
093     *          if the current thread cannot access the system thread group
094     *
095     * @throws  SecurityException  if the current thread cannot modify
096     *          thread groups from this thread's thread group up to the system thread group
097     */
098    public static Collection<Thread> findThreadsByName(final String threadName, final ThreadGroup threadGroup) {
099        return findThreads(threadGroup, false, new NamePredicate(threadName));
100    }
101
102    /**
103     * Return active threads with the specified name if they belong to a thread group with the specified group name.
104     *
105     * @param threadName The thread name
106     * @param threadGroupName The thread group name
107     * @return The threads which belongs to a thread group with the specified group name and the thread's name match the specified name,
108     * An empty collection is returned if no such thread exists. The collection returned is always unmodifiable.
109     * @throws IllegalArgumentException if the specified thread name or group name is null
110     * @throws  SecurityException
111     *          if the current thread cannot access the system thread group
112     *
113     * @throws  SecurityException  if the current thread cannot modify
114     *          thread groups from this thread's thread group up to the system thread group
115     */
116    public static Collection<Thread> findThreadsByName(final String threadName, final String threadGroupName) {
117        Validate.isTrue(threadName != null, "The thread name must not be null");
118        Validate.isTrue(threadGroupName != null, "The thread group name must not be null");
119
120        final Collection<ThreadGroup> threadGroups = findThreadGroups(new NamePredicate(threadGroupName));
121
122        if (threadGroups.isEmpty()) {
123            return Collections.emptyList();
124        }
125
126        final Collection<Thread> result = new ArrayList<>();
127        final NamePredicate threadNamePredicate = new NamePredicate(threadName);
128        for (final ThreadGroup group : threadGroups) {
129            result.addAll(findThreads(group, false, threadNamePredicate));
130        }
131        return Collections.unmodifiableCollection(result);
132    }
133
134    /**
135     * Return active thread groups with the specified group name.
136     *
137     * @param threadGroupName The thread group name
138     * @return the thread groups with the specified group name or an empty collection if no such thread group exists. The collection returned is always unmodifiable.
139     * @throws IllegalArgumentException if group name is null
140     * @throws  SecurityException
141     *          if the current thread cannot access the system thread group
142     *
143     * @throws  SecurityException  if the current thread cannot modify
144     *          thread groups from this thread's thread group up to the system thread group
145     */
146    public static Collection<ThreadGroup> findThreadGroupsByName(final String threadGroupName) {
147        return findThreadGroups(new NamePredicate(threadGroupName));
148    }
149
150    /**
151     * Return all active thread groups excluding the system thread group (A thread group is active if it has been not destroyed).
152     *
153     * @return all thread groups excluding the system thread group. The collection returned is always unmodifiable.
154     * @throws  SecurityException
155     *          if the current thread cannot access the system thread group
156     *
157     * @throws  SecurityException  if the current thread cannot modify
158     *          thread groups from this thread's thread group up to the system thread group
159     */
160    public static Collection<ThreadGroup> getAllThreadGroups() {
161        return findThreadGroups(ALWAYS_TRUE_PREDICATE);
162    }
163
164    /**
165     * Return the system thread group (sometimes also referred as "root thread group").
166     *
167     * @return the system thread group
168     * @throws  SecurityException  if the current thread cannot modify
169     *          thread groups from this thread's thread group up to the system thread group
170     */
171    public static ThreadGroup getSystemThreadGroup() {
172        ThreadGroup threadGroup = Thread.currentThread().getThreadGroup();
173        while (threadGroup.getParent() != null) {
174            threadGroup = threadGroup.getParent();
175        }
176        return threadGroup;
177    }
178
179    /**
180     * Return all active threads (A thread is active if it has been started and has not yet died).
181     *
182     * @return all active threads. The collection returned is always unmodifiable.
183     * @throws  SecurityException
184     *          if the current thread cannot access the system thread group
185     *
186     * @throws  SecurityException  if the current thread cannot modify
187     *          thread groups from this thread's thread group up to the system thread group
188     */
189    public static Collection<Thread> getAllThreads() {
190        return findThreads(ALWAYS_TRUE_PREDICATE);
191    }
192
193    /**
194     * Return active threads with the specified name.
195     *
196     * @param threadName The thread name
197     * @return The threads with the specified name or an empty collection if no such thread exists. The collection returned is always unmodifiable.
198     * @throws IllegalArgumentException if the specified name is null
199     * @throws  SecurityException
200     *          if the current thread cannot access the system thread group
201     *
202     * @throws  SecurityException  if the current thread cannot modify
203     *          thread groups from this thread's thread group up to the system thread group
204     */
205    public static Collection<Thread> findThreadsByName(final String threadName) {
206        return findThreads(new NamePredicate(threadName));
207    }
208
209    /**
210     * Return the active thread with the specified id.
211     *
212     * @param threadId The thread id
213     * @return The thread with the specified id or {@code null} if no such thread exists
214     * @throws IllegalArgumentException if the specified id is zero or negative
215     * @throws  SecurityException
216     *          if the current thread cannot access the system thread group
217     *
218     * @throws  SecurityException  if the current thread cannot modify
219     *          thread groups from this thread's thread group up to the system thread group
220     */
221    public static Thread findThreadById(final long threadId) {
222        final Collection<Thread> result = findThreads(new ThreadIdPredicate(threadId));
223        return result.isEmpty() ? null : result.iterator().next();
224    }
225
226    /**
227     * <p>
228     * ThreadUtils instances should NOT be constructed in standard programming. Instead, the class should be used as
229     * {@code ThreadUtils.getAllThreads()}
230     * </p>
231     * <p>
232     * This constructor is public to permit tools that require a JavaBean instance to operate.
233     * </p>
234     */
235    public ThreadUtils() {
236        super();
237    }
238
239    /**
240     * A predicate for selecting threads.
241     */
242    // When breaking BC, replace this with Predicate<Thread>
243    @FunctionalInterface
244    public interface ThreadPredicate {
245
246        /**
247         * Evaluates this predicate on the given thread.
248         * @param thread the thread
249         * @return {@code true} if the thread matches the predicate, otherwise {@code false}
250         */
251        boolean test(Thread thread);
252    }
253
254    /**
255     * A predicate for selecting threadgroups.
256     */
257    // When breaking BC, replace this with Predicate<ThreadGroup>
258    @FunctionalInterface
259    public interface ThreadGroupPredicate {
260
261        /**
262         * Evaluates this predicate on the given threadgroup.
263         * @param threadGroup the threadgroup
264         * @return {@code true} if the threadGroup matches the predicate, otherwise {@code false}
265         */
266        boolean test(ThreadGroup threadGroup);
267    }
268
269    /**
270     * Predicate which always returns true.
271     */
272    public static final AlwaysTruePredicate ALWAYS_TRUE_PREDICATE = new AlwaysTruePredicate();
273
274    /**
275     * A predicate implementation which always returns true.
276     */
277    private static final class AlwaysTruePredicate implements ThreadPredicate, ThreadGroupPredicate {
278
279        private AlwaysTruePredicate() {
280        }
281
282        @Override
283        public boolean test(final ThreadGroup threadGroup) {
284            return true;
285        }
286
287        @Override
288        public boolean test(final Thread thread) {
289            return true;
290        }
291    }
292
293    /**
294     * A predicate implementation which matches a thread or threadgroup name.
295     */
296    public static class NamePredicate implements ThreadPredicate, ThreadGroupPredicate {
297
298        private final String name;
299
300        /**
301         * Predicate constructor
302         *
303         * @param name thread or threadgroup name
304         * @throws IllegalArgumentException if the name is {@code null}
305         */
306        public NamePredicate(final String name) {
307            super();
308            Validate.isTrue(name != null, "The name must not be null");
309            this.name = name;
310        }
311
312        @Override
313        public boolean test(final ThreadGroup threadGroup) {
314            return threadGroup != null && threadGroup.getName().equals(name);
315        }
316
317        @Override
318        public boolean test(final Thread thread) {
319            return thread != null && thread.getName().equals(name);
320        }
321    }
322
323    /**
324     * A predicate implementation which matches a thread id.
325     */
326    public static class ThreadIdPredicate implements ThreadPredicate {
327
328        private final long threadId;
329
330        /**
331         * Predicate constructor
332         *
333         * @param threadId the threadId to match
334         * @throws IllegalArgumentException if the threadId is zero or negative
335         */
336        public ThreadIdPredicate(final long threadId) {
337            super();
338            if (threadId <= 0) {
339                throw new IllegalArgumentException("The thread id must be greater than zero");
340            }
341            this.threadId = threadId;
342        }
343
344        @Override
345        public boolean test(final Thread thread) {
346            return thread != null && thread.getId() == threadId;
347        }
348    }
349
350    /**
351     * Select all active threads which match the given predicate.
352     *
353     * @param predicate the predicate
354     * @return An unmodifiable {@code Collection} of active threads matching the given predicate
355     *
356     * @throws IllegalArgumentException if the predicate is null
357     * @throws  SecurityException
358     *          if the current thread cannot access the system thread group
359     * @throws  SecurityException  if the current thread cannot modify
360     *          thread groups from this thread's thread group up to the system thread group
361     */
362    public static Collection<Thread> findThreads(final ThreadPredicate predicate) {
363        return findThreads(getSystemThreadGroup(), true, predicate);
364    }
365
366    /**
367     * Select all active threadgroups which match the given predicate.
368     *
369     * @param predicate the predicate
370     * @return An unmodifiable {@code Collection} of active threadgroups matching the given predicate
371     * @throws IllegalArgumentException if the predicate is null
372     * @throws  SecurityException
373     *          if the current thread cannot access the system thread group
374     * @throws  SecurityException  if the current thread cannot modify
375     *          thread groups from this thread's thread group up to the system thread group
376     */
377    public static Collection<ThreadGroup> findThreadGroups(final ThreadGroupPredicate predicate) {
378        return findThreadGroups(getSystemThreadGroup(), true, predicate);
379    }
380
381    /**
382     * Select all active threads which match the given predicate and which belongs to the given thread group (or one of its subgroups).
383     *
384     * @param group the thread group
385     * @param recurse if {@code true} then evaluate the predicate recursively on all threads in all subgroups of the given group
386     * @param predicate the predicate
387     * @return An unmodifiable {@code Collection} of active threads which match the given predicate and which belongs to the given thread group
388     * @throws IllegalArgumentException if the given group or predicate is null
389     * @throws  SecurityException  if the current thread cannot modify
390     *          thread groups from this thread's thread group up to the system thread group
391     */
392    public static Collection<Thread> findThreads(final ThreadGroup group, final boolean recurse, final ThreadPredicate predicate) {
393        Validate.isTrue(group != null, "The group must not be null");
394        Validate.isTrue(predicate != null, "The predicate must not be null");
395
396        int count = group.activeCount();
397        Thread[] threads;
398        do {
399            threads = new Thread[count + (count / 2) + 1]; //slightly grow the array size
400            count = group.enumerate(threads, recurse);
401            //return value of enumerate() must be strictly less than the array size according to javadoc
402        } while (count >= threads.length);
403
404        final List<Thread> result = new ArrayList<>(count);
405        for (int i = 0; i < count; ++i) {
406            if (predicate.test(threads[i])) {
407                result.add(threads[i]);
408            }
409        }
410        return Collections.unmodifiableCollection(result);
411    }
412
413    /**
414     * Select all active threadgroups which match the given predicate and which is a subgroup of the given thread group (or one of its subgroups).
415     *
416     * @param group the thread group
417     * @param recurse if {@code true} then evaluate the predicate recursively on all threadgroups in all subgroups of the given group
418     * @param predicate the predicate
419     * @return An unmodifiable {@code Collection} of active threadgroups which match the given predicate and which is a subgroup of the given thread group
420     * @throws IllegalArgumentException if the given group or predicate is null
421     * @throws  SecurityException  if the current thread cannot modify
422     *          thread groups from this thread's thread group up to the system thread group
423     */
424    public static Collection<ThreadGroup> findThreadGroups(final ThreadGroup group, final boolean recurse, final ThreadGroupPredicate predicate) {
425        Validate.isTrue(group != null, "The group must not be null");
426        Validate.isTrue(predicate != null, "The predicate must not be null");
427
428        int count = group.activeGroupCount();
429        ThreadGroup[] threadGroups;
430        do {
431            threadGroups = new ThreadGroup[count + (count / 2) + 1]; //slightly grow the array size
432            count = group.enumerate(threadGroups, recurse);
433            //return value of enumerate() must be strictly less than the array size according to javadoc
434        } while (count >= threadGroups.length);
435
436        final List<ThreadGroup> result = new ArrayList<>(count);
437        for (int i = 0; i < count; ++i) {
438            if (predicate.test(threadGroups[i])) {
439                result.add(threadGroups[i]);
440            }
441        }
442        return Collections.unmodifiableCollection(result);
443    }
444}