Java multi-thread positioning deadlock--ThreadMXBean

Location deadlock-ThreadMXBean

Use ThreadMXBeanto detect the deadlocked thread in the program and obtain relevant information about the thread. Do some corresponding operations.

Compared with jstack viewing in the command. This way of writing code can do some corresponding operations when the thread is deadlocked.

The sample code is as follows:

package com.thread.deadlock;

import java.lang.management.ManagementFactory;
import java.lang.management.ThreadInfo;
import java.lang.management.ThreadMXBean;

/**
 * 类名称:ThreadMXBeanDetection
 * 类描述:  ThreadMXBean 检测死锁 
 *
 * @author: https://javaweixin6.blog.csdn.net/
 * 创建时间:2020/9/11 19:59
 * Version 1.0
 */
public class ThreadMXBeanDetection implements Runnable{
    
    
    //标记位, 不同的线程根据标记位执行不同的代码
    int flag = 1 ;

    //两把锁
    static Object o1 = new Object();
    static Object o2 = new Object();

    public static void main(String[] args) throws InterruptedException {
    
    
        ThreadMXBeanDetection r1 = new ThreadMXBeanDetection();
        ThreadMXBeanDetection r2 = new ThreadMXBeanDetection();
        //给不同的线程, 设置不同的标记位
        r1.flag=1;
        r2.flag=2;

        Thread t1 = new Thread(r1);
        Thread t2 = new Thread(r2);
        t1.start();
        t2.start();

        //让两个子线程执行
        Thread.sleep(1000);

        ThreadMXBean threadMXBean = ManagementFactory.getThreadMXBean();

        //获取发生死锁的线程id数组
        long[] deadlockedThreads = threadMXBean.findDeadlockedThreads();

        //判断发生死锁的线程是否为空
        if (deadlockedThreads != null && deadlockedThreads.length > 0) {
    
    

            for (int i = 0; i < deadlockedThreads.length; i++) {
    
    
                //传入发生死锁的线程id , 获取发生死锁的线程信息
                ThreadInfo threadInfo = threadMXBean.getThreadInfo(deadlockedThreads[i]);

                //打印出发生死锁线程的名称
                System.out.println("死锁的线程名称:  "+threadInfo.getThreadName());
            }
        }

    }

    @Override
    public void run() {
    
    
        //打印出标记位
        System.out.println("flag = "+flag);
        if (flag == 1) {
    
    
            synchronized (o1) {
    
    
                try {
    
    
                    //线程1持有锁o1, 并且等待500ms ,让线程2执行
                    Thread.sleep(500);
                } catch (InterruptedException e) {
    
    
                    e.printStackTrace();
                }
                //线程1尝试去获取锁o2
                synchronized (o2) {
    
    
                    System.out.println("线程1成功拿到两把锁");
                }

            }
        }

        if (flag == 2) {
    
    

            synchronized (o2) {
    
    

                try {
    
    
                    //持有锁o2, 并且等待500ms ,让线程1执行
                    Thread.sleep(500);
                } catch (InterruptedException e) {
    
    
                    e.printStackTrace();
                }

                //线程2尝试去获取锁o1
                synchronized (o1) {
    
    
                    System.out.println("线程2成功拿到两把锁");
                }
            }
        }
    }

}

The main code is as follows. Get all the deadlocked threads, traverse them, and get the habit information

of the deadlocked threads . The following deadlocked thread information can be obtained, this example is to print the thread name. The

running program is printed as follows, you can See that the deadlock thread name is successfully printed.