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Java的每个Thread都希望拥有自己的名称

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10/04
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一. 介绍

平时工作中可能会碰到排查多线程的bug，而在排查的时候，如果线程（单个线程或者是线程池的线程）没有一个比较明确的名称，那么在排查的时候就比较头疼，因为排查问题首先需要找出“问题线程”，如果连“问题线程”都找不到，就很难找出问题原因，本文就针对多线程中涉及到的线程池、线程组、线程名称，介绍如果对其进行设置名称，方便排查问题时快速定位。

二. 设置线程名称

2.1 使用Thread+Runnable接口形式

如果是使用实现Runnable接口，然后使用Thread构造器来直接创建线程时，有两种方式设置线程名称：

1.在调用Thread的构造器时，传入第二个参数即可，构造器定义如下

Thread Thread(Runnable target, String threadName)

2.调用Thread对象的setName方法，设置线程名称即可；

上面两种方法的示例代码如下：

package cn.ganlixin;import lombok.extern.slf4j.Slf4j;
import org.junit.Test;@Slf4j
public class DefineThreadName { /**
* 不设置线程名称，使用默认的线程名称
*/
@Test
public void defaultThreadName() {
new Thread(() -> {
String threadName = Thread.currentThread().getName();
String threadGroupName = Thread.currentThread().getThreadGroup().getName();
long threadId = Thread.currentThread().getId();
log.info("threadName:{}, threadGroupName:{}, threadId:{}", threadName, threadGroupName, threadId);
}).start();
// 输出 threadName:Thread-1, threadGroupName:main, threadId:13
} /**
* 自定义线程的名称
*/
@Test
public void customThreadName() {
// 方式一：指定Thread构造方法的第二个参数，也就是线程的名称
new Thread(() -> {
String threadName = Thread.currentThread().getName();
String threadGroupName = Thread.currentThread().getThreadGroup().getName();
long threadId = Thread.currentThread().getId();
log.info("threadName:{}, threadGroupName:{}, threadId:{}", threadName, threadGroupName, threadId);
}, "my-custom-thread-name-1").start(); // 输出 threadName:my-custom-thread-name-1, threadGroupName:main, threadId:13 // 方式二：使用Thread对象的setName方法，设置线程名称
Thread thread = new Thread(() -> {
String threadName = Thread.currentThread().getName();
String threadGroupName = Thread.currentThread().getThreadGroup().getName();
long threadId = Thread.currentThread().getId();
log.info("threadName:{}, threadGroupName:{}, threadId:{}", threadName, threadGroupName, threadId);
});
thread.setName("my-custom-thread-name-2");
thread.start();
// 输出 threadName:my-custom-thread-name-2, threadGroupName:main, threadId:14
}
}

2.2 继承Thread类的形式

如果是继承Thread类，那么可以在子类中调用Thread仅接受一个字符串作为线程名称的构造器，像下面这么做：

package cn.ganlixin;import lombok.extern.slf4j.Slf4j;
import org.junit.Test;@Slf4j
public class DefineThreadName { /**
* 自定义的继承自Thread的线程类
*/
private static class MyThread extends Thread {
private MyThread(String threadName) {
super(threadName); // Thread有一个构造器接收一个字符串类型的参数，作为线程名称
} @Override
public void run() {
// 因为继承自Thread，所以下面可以直接调用这些方法，而不需要通过Thread.currentThread()获取当前线程
String threadName = getName();
String threadGroupName = getThreadGroup().getName();
long threadId = getId();
log.info("threadName:{}, threadGroupName:{}, threadId:{}", threadName, threadGroupName, threadId);
}
} /**
* 测试设置、更改线程名称
*/
@Test
public void testInheritThread() {
MyThread t1 = new MyThread("my-extends-thread-name-1");
t1.start();
// 输出 threadName:my-extends-thread-name-1, threadGroupName:main, threadId:13 MyThread t2 = new MyThread("my-extends-thread-name-2");
t2.setName("changed-thread-name"); // 手动修改线程名称
t2.start();
// 输出 threadName:changed-thread-name, threadGroupName:main, threadId:14
}
}

三. 设置线程组的名称

线程组名称需要在创建线程组的时候进行指定，然后使用线程组的时候将线程组作为Thread类的构造器参数传入即可，示例代码如下：

package cn.ganlixin.name;import lombok.extern.slf4j.Slf4j;
import org.junit.Test;@Slf4j
public class ThreadGroupName { @Test
public void defineThreadGroupName() {
// 定义一个线程组，传入线程组的名称（自定义）
ThreadGroup threadGroup = new ThreadGroup("my-thread-group-name"); Runnable runnable = () -> {
String threadGroupName = Thread.currentThread().getThreadGroup().getName();
String threadName = Thread.currentThread().getName();
long threadId = Thread.currentThread().getId(); log.info("threadGroupName:{}, threadName:{}, threadId:{}", threadGroupName, threadName, threadId);
}; Thread t1 = new Thread(threadGroup, runnable);
t1.start();
// 输出 threadGroupName:my-thread-group-name, threadName:Thread-1, threadId:13 // 第三个参数是线程名称
Thread t2 = new Thread(threadGroup, runnable, "my-thread-name");
t2.start();
// threadGroupName:my-thread-group-name, threadName:my-thread-name, threadId:14
}
}

四. 设置线程池名称

4.1 创建线程池的两种途径

创建线程池，有两种方式：

1.实例化ThreadPoolExecutor来创建线程池，可以指定相关的参数，方法定义如下：

2.使用Executors的静态方法创建线程池，实际是对ThreadPoolExecutor对象的创建过程进行了封装，可用的方法定义如下：

上面的诸多定义中，提到了一个ThreadFactory，“线程工厂”，这是一个接口，定义了创建线程的统一规范，实现类需要重写newThread方法，定义如下：

package java.util.concurrent;public interface ThreadFactory {
Thread newThread(Runnable r);
}

当我们调用Executors或者使用ThreadPoolExecutor来创建线程池，如果没有指定ThreadFactory，那么就会使用默认的Executors.DefaultThreadFactory：

static class DefaultThreadFactory implements ThreadFactory {
private static final AtomicInteger poolNumber = new AtomicInteger(1);
private final ThreadGroup group;
private final AtomicInteger threadNumber = new AtomicInteger(1);
private final String namePrefix; DefaultThreadFactory() {
SecurityManager s = System.getSecurityManager();
group = (s != null) ? s.getThreadGroup() :
Thread.currentThread().getThreadGroup();
namePrefix = "pool-" +
poolNumber.getAndIncrement() +
"-thread-";
} public Thread newThread(Runnable r) {
Thread t = new Thread(group, r,
namePrefix + threadNumber.getAndIncrement(),
0);
if (t.isDaemon())
t.setDaemon(false);
if (t.getPriority() != Thread.NORM_PRIORITY)
t.setPriority(Thread.NORM_PRIORITY);
return t;
}
}

如果我们要对线程池中的线程创建进行扩展，那么实现ThreadFactory接口，加入自己的扩展即可，此处对于线程池中线程的名称进行设置，也是可以在这里实现。

4.2 自定义线程工厂（ThreadFactory)

自己实现ThreadFactory接口，可以参考Executors.DefaultThreadFactory，做一下细微的修改就行了，下面是我创建的NameableThreadFactory，意为“可命名的线程工厂”：

package cn.ganlixin.name;import org.apache.commons.lang3.StringUtils;import java.util.Objects;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicInteger;/**
* 描述:
* 参照Executors.DefaultThreadFactory，自定义ThreadFactory实现类
*
* @author ganlixin
* @create 2020-05-23
*/
public class NameableThreadFactory implements ThreadFactory {
/**
* 对线程池的数量进行计数，注意是类属性
*/
private static final AtomicInteger poolNumber = new AtomicInteger(1); /**
* 线程组名称
*/
private ThreadGroup group; /**
* 对线程池中的线程数据进行计数，注意是实例属性
*/
private final AtomicInteger threadNumber = new AtomicInteger(1); /**
* 线程名称的前缀
*/
private String namePrefix; /**
* Executors.DefaultThreadFactory中默认的方式（设置线程组、线程名称前缀）
*/
public NameableThreadFactory() {
SecurityManager s = System.getSecurityManager();
group = (s != null) ? s.getThreadGroup() : Thread.currentThread().getThreadGroup();
namePrefix = "pool-" + poolNumber.getAndIncrement() + "-thread-";
} /**
* 创建线程工厂，指定线程名称前缀
*
* @param threadNamePrefix 线程名称前缀
*/
public NameableThreadFactory(String threadNamePrefix) {
if (StringUtils.isBlank(threadNamePrefix)) {
throw new IllegalArgumentException("线程名称的前缀不能为空");
} // 线程组，仍旧使用旧规则
SecurityManager s = System.getSecurityManager();
group = (s != null) ? s.getThreadGroup() : Thread.currentThread().getThreadGroup(); // 指定线程的名称前缀，设置为传入的名称前缀
this.namePrefix = threadNamePrefix + "-";
} /**
* 创建线程工厂，指定线程组、以及线程名称前缀
*
* @param threadGroup 线程组实例
* @param threadNamePrefix 线程名称前缀
*/
public NameableThreadFactory(ThreadGroup threadGroup, String threadNamePrefix) {
if (Objects.isNull(threadGroup)) {
throw new IllegalArgumentException("线程组不能为空");
} if (StringUtils.isBlank(threadNamePrefix)) {
throw new IllegalArgumentException("线程名称的前缀不能为空");
} this.group = threadGroup;
this.namePrefix = threadNamePrefix + "-";
} public Thread newThread(Runnable r) {
Thread t = new Thread(group, r, namePrefix + threadNumber.getAndIncrement(), 0);
if (t.isDaemon()) {
t.setDaemon(false);
}
if (t.getPriority() != Thread.NORM_PRIORITY) {
t.setPriority(Thread.NORM_PRIORITY);
}
return t;
}
}

进行测试，因为Executors和ThreadPoolExecutor的本质是一样的，所以这里使用Executors进行测试，只需要在用到ThreadFactory的时候，引入自己的创建NameableThreadFactory即可：

package cn.ganlixin.name;import lombok.extern.slf4j.Slf4j;
import org.junit.Test;import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;@Slf4j
public class TestNameableThreadFactory { @Test
public void test() throws InterruptedException {
ExecutorService executorService1 = Executors.newFixedThreadPool(3, new NameableThreadFactory("自定义线程池one")); Runnable runnable = () -> {
String threadGroupName = Thread.currentThread().getThreadGroup().getName();
String threadName = Thread.currentThread().getName();
long threadId = Thread.currentThread().getId();
log.info("threadGroupName:{}, threadName:{}, threadId:{}", threadGroupName, threadName, threadId);
}; for (int i = 0; i < 3; i++) {
executorService1.submit(runnable);
}
// 输出
// threadGroupName:main, threadName:自定义线程池one-1, threadId:14
// threadGroupName:main, threadName:自定义线程池one-2, threadId:15
// threadGroupName:main, threadName:自定义线程池one-3, threadId:16
Thread.sleep(100); // 创建线程组
ThreadGroup threadGroup = new ThreadGroup("自定义线程组one");
ExecutorService executorService2 = Executors.newFixedThreadPool(3, new NameableThreadFactory(threadGroup, "自定义线程池two"));
for (int i = 0; i < 3; i++) {
executorService2.submit(runnable);
}
// 输出：
// threadGroupName:自定义线程组one, threadName:自定义线程池two-1, threadId:16
// threadGroupName:自定义线程组one, threadName:自定义线程池two-2, threadId:17
// threadGroupName:自定义线程组one, threadName:自定义线程池two-3, threadId:18 Thread.sleep(1000);
}
}