通过编程发现Java死锁-白红宇

通过stack也可以发现死锁。

测试类

import java.util.concurrent.TimeUnit;public class Test {    public static void main(String[] args) {        DeadlockDetector deadlockDetector = new DeadlockDetector(new DeadlockConsoleHandler(), 5, TimeUnit.SECONDS);        deadlockDetector.start();        final Object lock1 = new Object();        final Object lock2 = new Object();        Thread thread1 = new Thread(()->{            synchronized (lock1) {                System.out.println("Thread1 acquired lock1");                try {                    TimeUnit.MILLISECONDS.sleep(500);                } catch (InterruptedException ignore) {                }                synchronized (lock2) {                    System.out.println("Thread1 acquired lock2");                }            }        });        thread1.start();        Thread thread2 = new Thread(()->{            synchronized (lock2) {                System.out.println("Thread2 acquired lock2");                synchronized (lock1) {                    System.out.println("Thread2 acquired lock1");                }            }        });        thread2.start();    }}

处理类

public class DeadlockConsoleHandler implements DeadlockHandler {    @Override    public void handleDeadlock(final ThreadInfo[] deadlockedThreads) {        if (deadlockedThreads != null) {            System.err.println("Deadlock detected!");            Map
     
       stackTraceMap = Thread.getAllStackTraces();            for (ThreadInfo threadInfo : deadlockedThreads) {                if (threadInfo != null) {                    for (Thread thread : Thread.getAllStackTraces().keySet()) {                        if (thread.getId() == threadInfo.getThreadId()) {                            System.err.println(threadInfo.toString().trim());                            for (StackTraceElement ste : thread.getStackTrace()) {                                System.err.println("t" + ste.toString().trim());                            }                        }                    }                }            }        }    }}import java.lang.management.ThreadInfo;public interface DeadlockHandler {    void handleDeadlock(final ThreadInfo[] deadlockedThreads);}

关键类

import java.lang.management.ManagementFactory;import java.lang.management.ThreadInfo;import java.lang.management.ThreadMXBean;import java.util.concurrent.Executors;import java.util.concurrent.ScheduledExecutorService;import java.util.concurrent.TimeUnit;public class DeadlockDetector {    private final DeadlockHandler deadlockHandler;    private final long period;    private final TimeUnit unit;    private final ThreadMXBean mbean = ManagementFactory.getThreadMXBean();    private final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);    final Runnable deadlockCheck = new Runnable() {        @Override        public void run() {            long[] deadlockedThreadIds = mbean.findDeadlockedThreads();            if (deadlockedThreadIds != null) {                ThreadInfo[] threadInfos = mbean.getThreadInfo(deadlockedThreadIds);                deadlockHandler.handleDeadlock(threadInfos);            }        }    };    public DeadlockDetector(final DeadlockHandler deadlockHandler, final long period, final TimeUnit unit) {        this.deadlockHandler = deadlockHandler;        this.period = period;        this.unit = unit;    }    public void start() {        this.scheduler.scheduleAtFixedRate(this.deadlockCheck, this.period, this.period, this.unit);    }}

测试结果

Thread1 acquired lock1Thread2 acquired lock2Deadlock detected!"Thread-1" Id=12 BLOCKED on java.lang.Object@6a80bb83 owned by "Thread-0" Id=11ttest.Test.lambda$main$1(Test.java:32)ttest.Test$$Lambda$2/363771819.run(Unknown Source)tjava.lang.Thread.run(Thread.java:745)"Thread-0" Id=11 BLOCKED on java.lang.Object@6ebf220b owned by "Thread-1" Id=12ttest.Test.lambda$main$0(Test.java:23)ttest.Test$$Lambda$1/668386784.run(Unknown Source)tjava.lang.Thread.run(Thread.java:745)Deadlock detected!