jstack:Java堆栈跟踪工具

jstack（Stack  Trace  for  Java）命令用于生成虚拟机当前时刻的线程快照（一般称为threaddump或者javacore文件）。线程快照就是当前虚拟机内每一条线程正在执行的方法堆栈的集合，生成线程快照的主要目的是定位线程出现长时间停顿的原因，如线程间死锁、死循环、请求外部资源导致的长时间等待等都是导致线程长时间停顿的常见原因。线程出现停顿的时候通过jstack来查看各个线程的调用堆栈，就可以知道没有响应的线程到底在后台做些什么事情，或者等待着什么资源。

命令格式:

jstack [option] vmid



例子:

C:\Users\hasee>jstack -l 14800

2017-11-08 15:13:07

Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.66-b17 mixed mode):

"http-apr-8080-exec-10" #50 daemon prio=5 os_prio=0 tid=0x000000002007e800 nid=0x3108 waiting on co
4000
ndition [0x00000000312ce000]

   java.lang.Thread.State: WAITING (parking)

        at sun.misc.Unsafe.park(Native Method)

        - parking to wait for  <0x00000006c2bfb310> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)

        at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)

        at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)

        at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)

        at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:103)

        at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:31)

        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 org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)

        at java.lang.Thread.run(Thread.java:745)

   Locked ownable synchronizers:

        - None

"http-apr-8080-exec-9" #49 daemon prio=5 os_prio=0 tid=0x000000002007e000 nid=0x47cc waiting on condition [0x00000000311ce000]

   java.lang.Thread.State: WAITING (parking)

        at sun.misc.Unsafe.park(Native Method)

        - parking to wait for  <0x00000006c2bfb310> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)

        at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)

        at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)

        at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)

        at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:103)

        at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:31)

        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 org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)

        at java.lang.Thread.run(Thread.java:745)

   Locked ownable synchronizers:

        - None

"http-apr-8080-exec-8" #48 daemon prio=5 os_prio=0 tid=0x000000002007d000 nid=0x4364 waiting on condition [0x00000000310ce000]

   java.lang.Thread.State: WAITING (parking)

        at sun.misc.Unsafe.park(Native Method)

        - parking to wait for  <0x00000006c2bfb310> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)

        at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)

        at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)

        at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)

        at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:103)

        at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:31)

        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 org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)

        at java.lang.Thread.run(Thread.java:745)

   Locked ownable synchronizers:

        - None

..........................

在JDK  1.5中，java.lang.Thread类新增了一个getAllStackTraces（）方法用于获取虚拟机中所有线程的StackTraceElement对象。使用这个方法可以通过简单的几行代码就完成jstack的大部分功能，在实际项目中不妨调用这个方法做个管理员页面，可以随时使用浏览器来查看线程堆栈:

<%@page import="java.util.Map"%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>服务器线程信息</title>
</head>
<body>
<pre>
<%
for( Map.Entry<Thread,StackTraceElement[]>stackTrace : Thread.getAllStackTraces().entrySet() ){
Thread thread = (Thread)stackTrace.getKey();
StackTraceElement[] stack = (StackTraceElement[])stackTrace.getValue();
if(thread.equals(Thread.currentThread())){
continue;
}
out.print("\n线程："+thread.getName()+"\n");
for(StackTraceElement element : stack){
out.print("\t"+element+"\n");
}
}
%>
</pre>
</body>
</html>