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With inspiration from other libraries
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.commons.lang3;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
/**
*
* Helpers for {@code java.lang.Thread} and {@code java.lang.ThreadGroup}.
*
*
* #ThreadSafe#
*
*
* @see java.lang.Thread
* @see java.lang.ThreadGroup
* @since 3.5
*/
public class ThreadUtils {
/**
* Return the active thread with the specified id if it belongs to the specified thread group.
*
* @param threadId The thread id
* @param threadGroup The thread group
* @return The thread which belongs to a specified thread group and the thread's id match the specified id.
* {@code null} is returned if no such thread exists
* @throws IllegalArgumentException if the specified id is zero or negative or the group is null
* @throws SecurityException
* if the current thread cannot access the system thread group
*
* @throws SecurityException if the current thread cannot modify
* thread groups from this thread's thread group up to the system thread group
*/
public static Thread findThreadById(final long threadId, final ThreadGroup threadGroup) {
Validate.isTrue(threadGroup != null, "The thread group must not be null");
final Thread thread = findThreadById(threadId);
if(thread != null && threadGroup.equals(thread.getThreadGroup())) {
return thread;
}
return null;
}
/**
* Return the active thread with the specified id if it belongs to a thread group with the specified group name.
*
* @param threadId The thread id
* @param threadGroupName The thread group name
* @return The threads which belongs to a thread group with the specified group name and the thread's id match the specified id.
* {@code null} is returned if no such thread exists
* @throws IllegalArgumentException if the specified id is zero or negative or the group name is null
* @throws SecurityException
* if the current thread cannot access the system thread group
*
* @throws SecurityException if the current thread cannot modify
* thread groups from this thread's thread group up to the system thread group
*/
public static Thread findThreadById(final long threadId, final String threadGroupName) {
Validate.isTrue(threadGroupName != null, "The thread group name must not be null");
final Thread thread = findThreadById(threadId);
if(thread != null && thread.getThreadGroup() != null && thread.getThreadGroup().getName().equals(threadGroupName)) {
return thread;
}
return null;
}
/**
* Return active threads with the specified name if they belong to a specified thread group.
*
* @param threadName The thread name
* @param threadGroup The thread group
* @return The threads which belongs to a thread group and the thread's name match the specified name,
* An empty collection is returned if no such thread exists. The collection returned is always unmodifiable.
* @throws IllegalArgumentException if the specified thread name or group is null
* @throws SecurityException
* if the current thread cannot access the system thread group
*
* @throws SecurityException if the current thread cannot modify
* thread groups from this thread's thread group up to the system thread group
*/
public static Collection findThreadsByName(final String threadName, final ThreadGroup threadGroup) {
return findThreads(threadGroup, false, new NamePredicate(threadName));
}
/**
* Return active threads with the specified name if they belong to a thread group with the specified group name.
*
* @param threadName The thread name
* @param threadGroupName The thread group name
* @return The threads which belongs to a thread group with the specified group name and the thread's name match the specified name,
* An empty collection is returned if no such thread exists. The collection returned is always unmodifiable.
* @throws IllegalArgumentException if the specified thread name or group name is null
* @throws SecurityException
* if the current thread cannot access the system thread group
*
* @throws SecurityException if the current thread cannot modify
* thread groups from this thread's thread group up to the system thread group
*/
public static Collection findThreadsByName(final String threadName, final String threadGroupName) {
Validate.isTrue(threadName != null, "The thread name must not be null");
Validate.isTrue(threadGroupName != null, "The thread group name must not be null");
final Collection threadGroups = findThreadGroups(new NamePredicate(threadGroupName));
if(threadGroups.isEmpty()) {
return Collections.emptyList();
}
final Collection result = new ArrayList<>();
final NamePredicate threadNamePredicate = new NamePredicate(threadName);
for(final ThreadGroup group : threadGroups) {
result.addAll(findThreads(group, false, threadNamePredicate));
}
return Collections.unmodifiableCollection(result);
}
/**
* Return active thread groups with the specified group name.
*
* @param threadGroupName The thread group name
* @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.
* @throws IllegalArgumentException if group name is null
* @throws SecurityException
* if the current thread cannot access the system thread group
*
* @throws SecurityException if the current thread cannot modify
* thread groups from this thread's thread group up to the system thread group
*/
public static Collection findThreadGroupsByName(final String threadGroupName) {
return findThreadGroups(new NamePredicate(threadGroupName));
}
/**
* Return all active thread groups excluding the system thread group (A thread group is active if it has been not destroyed).
*
* @return all thread groups excluding the system thread group. The collection returned is always unmodifiable.
* @throws SecurityException
* if the current thread cannot access the system thread group
*
* @throws SecurityException if the current thread cannot modify
* thread groups from this thread's thread group up to the system thread group
*/
public static Collection getAllThreadGroups() {
return findThreadGroups(ALWAYS_TRUE_PREDICATE);
}
/**
* Return the system thread group (sometimes also referred as "root thread group").
*
* @return the system thread group
* @throws SecurityException if the current thread cannot modify
* thread groups from this thread's thread group up to the system thread group
*/
public static ThreadGroup getSystemThreadGroup() {
ThreadGroup threadGroup = Thread.currentThread().getThreadGroup();
while(threadGroup.getParent() != null) {
threadGroup = threadGroup.getParent();
}
return threadGroup;
}
/**
* Return all active threads (A thread is active if it has been started and has not yet died).
*
* @return all active threads. The collection returned is always unmodifiable.
* @throws SecurityException
* if the current thread cannot access the system thread group
*
* @throws SecurityException if the current thread cannot modify
* thread groups from this thread's thread group up to the system thread group
*/
public static Collection getAllThreads() {
return findThreads(ALWAYS_TRUE_PREDICATE);
}
/**
* Return active threads with the specified name.
*
* @param threadName The thread name
* @return The threads with the specified name or an empty collection if no such thread exists. The collection returned is always unmodifiable.
* @throws IllegalArgumentException if the specified name is null
* @throws SecurityException
* if the current thread cannot access the system thread group
*
* @throws SecurityException if the current thread cannot modify
* thread groups from this thread's thread group up to the system thread group
*/
public static Collection findThreadsByName(final String threadName) {
return findThreads(new NamePredicate(threadName));
}
/**
* Return the active thread with the specified id.
*
* @param threadId The thread id
* @return The thread with the specified id or {@code null} if no such thread exists
* @throws IllegalArgumentException if the specified id is zero or negative
* @throws SecurityException
* if the current thread cannot access the system thread group
*
* @throws SecurityException if the current thread cannot modify
* thread groups from this thread's thread group up to the system thread group
*/
public static Thread findThreadById(final long threadId) {
final Collection result = findThreads(new ThreadIdPredicate(threadId));
return result.isEmpty() ? null : result.iterator().next();
}
/**
*
* ThreadUtils instances should NOT be constructed in standard programming. Instead, the class should be used as
* {@code ThreadUtils.getAllThreads()}
*
*
* This constructor is public to permit tools that require a JavaBean instance to operate.
*
*/
public ThreadUtils() {
super();
}
/**
* A predicate for selecting threads.
*/
//if java minimal version for lang becomes 1.8 extend this interface from java.util.function.Predicate
public interface ThreadPredicate /*extends java.util.function.Predicate*/{
/**
* Evaluates this predicate on the given thread.
* @param thread the thread
* @return {@code true} if the thread matches the predicate, otherwise {@code false}
*/
boolean test(Thread thread);
}
/**
* A predicate for selecting threadgroups.
*/
//if java minimal version for lang becomes 1.8 extend this interface from java.util.function.Predicate
public interface ThreadGroupPredicate /*extends java.util.function.Predicate*/{
/**
* Evaluates this predicate on the given threadgroup.
* @param threadGroup the threadgroup
* @return {@code true} if the threadGroup matches the predicate, otherwise {@code false}
*/
boolean test(ThreadGroup threadGroup);
}
/**
* Predicate which always returns true.
*/
public static final AlwaysTruePredicate ALWAYS_TRUE_PREDICATE = new AlwaysTruePredicate();
/**
* A predicate implementation which always returns true.
*/
private static final class AlwaysTruePredicate implements ThreadPredicate, ThreadGroupPredicate{
private AlwaysTruePredicate() {
}
@Override
public boolean test(final ThreadGroup threadGroup) {
return true;
}
@Override
public boolean test(final Thread thread) {
return true;
}
}
/**
* A predicate implementation which matches a thread or threadgroup name.
*/
public static class NamePredicate implements ThreadPredicate, ThreadGroupPredicate {
private final String name;
/**
* Predicate constructor
*
* @param name thread or threadgroup name
* @throws IllegalArgumentException if the name is {@code null}
*/
public NamePredicate(final String name) {
super();
Validate.isTrue(name != null, "The name must not be null");
this.name = name;
}
@Override
public boolean test(final ThreadGroup threadGroup) {
return threadGroup != null && threadGroup.getName().equals(name);
}
@Override
public boolean test(final Thread thread) {
return thread != null && thread.getName().equals(name);
}
}
/**
* A predicate implementation which matches a thread id.
*/
public static class ThreadIdPredicate implements ThreadPredicate {
private final long threadId;
/**
* Predicate constructor
*
* @param threadId the threadId to match
* @throws IllegalArgumentException if the threadId is zero or negative
*/
public ThreadIdPredicate(final long threadId) {
super();
if (threadId <= 0) {
throw new IllegalArgumentException("The thread id must be greater than zero");
}
this.threadId = threadId;
}
@Override
public boolean test(final Thread thread) {
return thread != null && thread.getId() == threadId;
}
}
/**
* Select all active threads which match the given predicate.
*
* @param predicate the predicate
* @return An unmodifiable {@code Collection} of active threads matching the given predicate
*
* @throws IllegalArgumentException if the predicate is null
* @throws SecurityException
* if the current thread cannot access the system thread group
* @throws SecurityException if the current thread cannot modify
* thread groups from this thread's thread group up to the system thread group
*/
public static Collection findThreads(final ThreadPredicate predicate){
return findThreads(getSystemThreadGroup(), true, predicate);
}
/**
* Select all active threadgroups which match the given predicate.
*
* @param predicate the predicate
* @return An unmodifiable {@code Collection} of active threadgroups matching the given predicate
* @throws IllegalArgumentException if the predicate is null
* @throws SecurityException
* if the current thread cannot access the system thread group
* @throws SecurityException if the current thread cannot modify
* thread groups from this thread's thread group up to the system thread group
*/
public static Collection findThreadGroups(final ThreadGroupPredicate predicate){
return findThreadGroups(getSystemThreadGroup(), true, predicate);
}
/**
* Select all active threads which match the given predicate and which belongs to the given thread group (or one of its subgroups).
*
* @param group the thread group
* @param recurse if {@code true} then evaluate the predicate recursively on all threads in all subgroups of the given group
* @param predicate the predicate
* @return An unmodifiable {@code Collection} of active threads which match the given predicate and which belongs to the given thread group
* @throws IllegalArgumentException if the given group or predicate is null
* @throws SecurityException if the current thread cannot modify
* thread groups from this thread's thread group up to the system thread group
*/
public static Collection findThreads(final ThreadGroup group, final boolean recurse, final ThreadPredicate predicate) {
Validate.isTrue(group != null, "The group must not be null");
Validate.isTrue(predicate != null, "The predicate must not be null");
int count = group.activeCount();
Thread[] threads;
do {
threads = new Thread[count + (count / 2) + 1]; //slightly grow the array size
count = group.enumerate(threads, recurse);
//return value of enumerate() must be strictly less than the array size according to javadoc
} while (count >= threads.length);
final List result = new ArrayList<>(count);
for (int i = 0; i < count; ++i) {
if (predicate.test(threads[i])) {
result.add(threads[i]);
}
}
return Collections.unmodifiableCollection(result);
}
/**
* Select all active threadgroups which match the given predicate and which is a subgroup of the given thread group (or one of its subgroups).
*
* @param group the thread group
* @param recurse if {@code true} then evaluate the predicate recursively on all threadgroups in all subgroups of the given group
* @param predicate the predicate
* @return An unmodifiable {@code Collection} of active threadgroups which match the given predicate and which is a subgroup of the given thread group
* @throws IllegalArgumentException if the given group or predicate is null
* @throws SecurityException if the current thread cannot modify
* thread groups from this thread's thread group up to the system thread group
*/
public static Collection findThreadGroups(final ThreadGroup group, final boolean recurse, final ThreadGroupPredicate predicate){
Validate.isTrue(group != null, "The group must not be null");
Validate.isTrue(predicate != null, "The predicate must not be null");
int count = group.activeGroupCount();
ThreadGroup[] threadGroups;
do {
threadGroups = new ThreadGroup[count + (count / 2) + 1]; //slightly grow the array size
count = group.enumerate(threadGroups, recurse);
//return value of enumerate() must be strictly less than the array size according to javadoc
} while(count >= threadGroups.length);
final List result = new ArrayList<>(count);
for(int i = 0; i < count; ++i) {
if(predicate.test(threadGroups[i])) {
result.add(threadGroups[i]);
}
}
return Collections.unmodifiableCollection(result);
}
}