windows下 的 jvisualvm,jstack参数查看运行程序的线程状况。

今天在复习多线程的时候写了一个死锁，突然看到网上有人用jstack的命令参数可以查看程序中每个线程的运行情况，于是就尝试着自己动手操作了一下。在cmd下运行jstack -h 

看到图中有一个jstack中所有的命令后面都要接上一个pid（进程id，就是我们运行程序的id）。但是这个我不知道啊。于是又去网上找了一些博客看了一下。发现了jvisualvm这个参数，抱着试试看的心里。在dos命令行中输入jvisualvm。输入之后才发现了自己学习java一直错过了一个新天地。

这里面不仅有我们现在运行程序的pid还有我们程序线程的运行状态，还有jvm底层参数的各种信息，而且是图形化界面。

好了，这个东西以后慢慢再研究，可以当成我们学习并发编程的一个监控工具使用。

因为我写了一个死锁程序。我在dos命令行中启动死锁程序：

死锁代码

public class DeadLock extends Thread
{
    public static Object m=new Object();
    public  static Object n=new Object();
    public   static  void dead() throws InterruptedException {
        synchronized (m){
            Thread.sleep(2000);
            synchronized (n) {
                System.out.println(1);
            }
        }
    }
    public static void d()
    {
        synchronized (n)
        {
            synchronized (m)
            {
                System.out.println(2);
            }
        }
    }
    public static void main(String[] args){
        DeadLock lock=new DeadLock();
        Thread t1=new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    dead();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });t1.start();
        Thread t2=new Thread(new Runnable() {
            @Override
            public void run() {
                d();
            }
        });t2.start();
    }
}

可以看到完全锁住了。

我们使用jvisualvm代开图形化工具查看死锁程序的pid

其实我们在这里面就可以看到visualvm会给我们报错，发现死锁。Thread-1，Thread-2处于监视状态。我们看到程序的pid为122480.。在dos命令行中输入 jstack -l 122480

如图中所示，线程二想要去获取对象m的监视器锁，而这个锁被线程一所占有，线程一想要去获取对象n的监视器锁，而这个锁被线程二所占有。

 

除开Thread-1和Thread-2之外，其实jstack罗列了所有的线程。

 

d:\java>jstack -l 122480
2018-08-21 17:08:19
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.112-b15 mixed mode):

"JMX server connection timeout 19" #19 daemon prio=5 os_prio=0 tid=0x000000001bef4000 nid=0x199ec in Object.wait() [0x000000001c6ff000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at com.sun.jmx.remote.internal.ServerCommunicatorAdmin$Timeout.run(ServerCommunicatorAdmin.java:168)
        - locked <0x00000000d7a10178> (a [I)
        at java.lang.Thread.run(Thread.java:745)

   Locked ownable synchronizers:
        - None

"RMI Scheduler(0)" #18 daemon prio=5 os_prio=0 tid=0x000000001bef3000 nid=0x1b320 waiting on condition [0x000000001c5fe000]
   java.lang.Thread.State: TIMED_WAITING (parking)
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x00000000d7a00730> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
        at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078)
        at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1093)
        at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809)
        at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)

   Locked ownable synchronizers:
        - None

"RMI TCP Connection(1)-192.168.1.104" #17 daemon prio=5 os_prio=0 tid=0x000000001a74d800 nid=0x1def0 runnable [0x000000001bcfe000]
   java.lang.Thread.State: RUNNABLE
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
        at java.net.SocketInputStream.read(SocketInputStream.java:170)
        at java.net.SocketInputStream.read(SocketInputStream.java:141)
        at java.io.BufferedInputStream.fill(BufferedInputStream.java:246)
        at java.io.BufferedInputStream.read(BufferedInputStream.java:265)
        - locked <0x00000000d7a18818> (a java.io.BufferedInputStream)
        at java.io.FilterInputStream.read(FilterInputStream.java:83)
        at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:550)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:826)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:683)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$1/1821163498.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:682)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)

   Locked ownable synchronizers:
        - <0x00000000d7a6afd0> (a java.util.concurrent.ThreadPoolExecutor$Worker)

"RMI TCP Accept-0" #16 daemon prio=5 os_prio=0 tid=0x000000001a692000 nid=0x1dd38 runnable [0x000000001bafe000]
   java.lang.Thread.State: RUNNABLE
        at java.net.DualStackPlainSocketImpl.accept0(Native Method)
        at java.net.DualStackPlainSocketImpl.socketAccept(DualStackPlainSocketImpl.java:131)
        at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:409)
        at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:199)
        - locked <0x00000000d7a08940> (a java.net.SocksSocketImpl)
        at java.net.ServerSocket.implAccept(ServerSocket.java:545)
        at java.net.ServerSocket.accept(ServerSocket.java:513)
        at sun.management.jmxremote.LocalRMIServerSocketFactory$1.accept(LocalRMIServerSocketFactory.java:52)
        at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.executeAcceptLoop(TCPTransport.java:400)
        at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.run(TCPTransport.java:372)
        at java.lang.Thread.run(Thread.java:745)

   Locked ownable synchronizers:
        - None

"DestroyJavaVM" #14 prio=5 os_prio=0 tid=0x0000000003390800 nid=0x1df64 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"Thread-2" #13 prio=5 os_prio=0 tid=0x000000001a532000 nid=0x1d78c waiting for monitor entry [0x000000001b2fe000]
   java.lang.Thread.State: BLOCKED (on object monitor)
        at DeadLock.d(DeadLock.java:22)
        - waiting to lock <0x00000000d7a20300> (a java.lang.Object)
        - locked <0x00000000d7a202f0> (a java.lang.Object)
        at DeadLock$2.run(DeadLock.java:42)
        at java.lang.Thread.run(Thread.java:745)

   Locked ownable synchronizers:
        - None

"Thread-1" #12 prio=5 os_prio=0 tid=0x000000001a531000 nid=0x1df58 waiting for monitor entry [0x000000001b1ff000]
   java.lang.Thread.State: BLOCKED (on object monitor)
        at DeadLock.dead(DeadLock.java:11)
        - waiting to lock <0x00000000d7a202f0> (a java.lang.Object)
        - locked <0x00000000d7a20300> (a java.lang.Object)
        at DeadLock$1.run(DeadLock.java:33)
        at java.lang.Thread.run(Thread.java:745)

   Locked ownable synchronizers:
        - None

"Service Thread" #10 daemon prio=9 os_prio=0 tid=0x000000001a4a9800 nid=0x1d1c8 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"C1 CompilerThread3" #9 daemon prio=9 os_prio=2 tid=0x000000001a432800 nid=0x1da7c waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"C2 CompilerThread2" #8 daemon prio=9 os_prio=2 tid=0x000000001a42e800 nid=0x1dd68 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"C2 CompilerThread1" #7 daemon prio=9 os_prio=2 tid=0x000000001a420800 nid=0x1d028 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"C2 CompilerThread0" #6 daemon prio=9 os_prio=2 tid=0x000000001a41e800 nid=0x1dd70 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x000000001a419800 nid=0x1d638 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x000000001a3c7000 nid=0x1a310 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"Finalizer" #3 daemon prio=8 os_prio=1 tid=0x0000000018492800 nid=0x1dffc in Object.wait() [0x000000001a88f000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
        - locked <0x00000000d7a382f8> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)
        at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)

   Locked ownable synchronizers:
        - None

"Reference Handler" #2 daemon prio=10 os_prio=2 tid=0x0000000003486000 nid=0x1de38 in Object.wait() [0x000000001a38f000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at java.lang.Object.wait(Object.java:502)
        at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
        - locked <0x00000000d7a30a48> (a java.lang.ref.Reference$Lock)
        at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)

   Locked ownable synchronizers:
        - None

"VM Thread" os_prio=2 tid=0x0000000018488800 nid=0x1dcec runnable

"GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00000000033a6800 nid=0x1dda0 runnable

"GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00000000033a8000 nid=0x1dde8 runnable

"GC task thread#2 (ParallelGC)" os_prio=0 tid=0x00000000033a9800 nid=0x1cea0 runnable

"GC task thread#3 (ParallelGC)" os_prio=0 tid=0x00000000033ab000 nid=0x1d338 runnable

"GC task thread#4 (ParallelGC)" os_prio=0 tid=0x00000000033ad800 nid=0x1aee4 runnable

"GC task thread#5 (ParallelGC)" os_prio=0 tid=0x00000000033ae800 nid=0x1da8c runnable

"GC task thread#6 (ParallelGC)" os_prio=0 tid=0x00000000033b2000 nid=0x1d2c4 runnable

"GC task thread#7 (ParallelGC)" os_prio=0 tid=0x00000000033b3000 nid=0x14a3c runnable

"VM Periodic Task Thread" os_prio=2 tid=0x000000001a526800 nid=0x1d74c waiting on condition

JNI global references: 242

Found one Java-level deadlock:
=============================
"Thread-2":
  waiting to lock monitor 0x0000000018490cb8 (object 0x00000000d7a20300, a java.lang.Object),
  which is held by "Thread-1"
"Thread-1":
  waiting to lock monitor 0x0000000018492158 (object 0x00000000d7a202f0, a java.lang.Object),
  which is held by "Thread-2"

Java stack information for the threads listed above:
===================================================
"Thread-2":
        at DeadLock.d(DeadLock.java:22)
        - waiting to lock <0x00000000d7a20300> (a java.lang.Object)
        - locked <0x00000000d7a202f0> (a java.lang.Object)
        at DeadLock$2.run(DeadLock.java:42)
        at java.lang.Thread.run(Thread.java:745)
"Thread-1":
        at DeadLock.dead(DeadLock.java:11)
        - waiting to lock <0x00000000d7a202f0> (a java.lang.Object)
        - locked <0x00000000d7a20300> (a java.lang.Object)
        at DeadLock$1.run(DeadLock.java:33)
        at java.lang.Thread.run(Thread.java:745)

Found 1 deadlock.

这么多线程其实我也还搞不懂，只是想帮助大家学会使用一些java的底层工具。底层的东西可以让我们更加深入的了解一门语言，写出更安全，更漂亮，更高效的代码。