jconsole, jstat, jmap, jstack, gc

通过工具jconsole查看：

直接执行命令:jconsole即可，通过jconsole可以手动执行gc，检测死锁，查看内存信息

一：分析死锁：

参考资料（http://www.cnblogs.com/ilahsa/archive/2013/06/03/3115410.html）

模拟死锁代码：DemoServiceImpl.java

package com.tch.test.dubbo_service_provider.serviceImpl;import com.tch.test.dubbo_service_model.service.DemoService;public class DemoServiceImpl implements DemoService {private Object resource1 = new Object();private Object resource2 = new Object();public String sayHello(String name) {deadLock();return "Hello " + name;}public void deadLock(){lockResource1();lockResource2();}private void lockResource1() {new Thread(new Runnable() {public void run() {synchronized(resource1){System.out.println(Thread.currentThread().getId() + ": i have get the lock of resource1");try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(Thread.currentThread().getId() + ": i begin to get the lock of resource2");synchronized(resource2){System.out.println(Thread.currentThread().getId() + ": i have get the lock of resource2");}}				}}).start();}private void lockResource2() {new Thread(new Runnable() {public void run() {synchronized(resource2){System.out.println(Thread.currentThread().getId() + ": i have get the lock of resource2");try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(Thread.currentThread().getId() + ": i begin to get the lock of resource1");synchronized(resource1){System.out.println(Thread.currentThread().getId() + ": i have get the lock of resource1");}}				}}).start();}}

执行命令：

jps

显示出Java进程，其中5900 Jps是我们执行jps的进程，6464 Provider则是我们应用程序的进程，6464也就是我们需要的进程号。

6464 Provider

2712

5900 Jps

然后执行：jstack -l 6464

就会显示出来很多信息，其中信息的最后是：

Found one Java-level deadlock:

=============================

"Thread-2":

  waiting to lock monitor 0x0000000057437088 (object 0x00000000d5db1d70, a java.lang.Object),

  which is held by "Thread-1"

"Thread-1":

  waiting to lock monitor 0x0000000057436b08 (object 0x00000000d5db1d80, a java.lang.Object),

  which is held by "Thread-2"

Java stack information for the threads listed above:

===================================================

"Thread-2":

        at com.tch.test.dubbo_service_provider.serviceImpl.DemoServiceImpl$2.run(DemoServiceImpl.java:52)

        - waiting to lock <0x00000000d5db1d70> (a java.lang.Object)

        - locked <0x00000000d5db1d80> (a java.lang.Object)

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

"Thread-1":

        at com.tch.test.dubbo_service_provider.serviceImpl.DemoServiceImpl$1.run(DemoServiceImpl.java:33)

        - waiting to lock <0x00000000d5db1d80> (a java.lang.Object)

        - locked <0x00000000d5db1d70> (a java.lang.Object)

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

Found 1 deadlock.

明确显示了死锁的位置。。。

二：查看应用程序的内存信息：

参考资料（http://liudaoru.iteye.com/blog/540772）

执行：jmap -dump:format=b,file=dumpFile.bin 6464

会在当前目录生成文件：dumpFile.bin，就可以查看应用程序（jps显示的进程号：6464）内存信息，包含有哪些对象等等

但是该文件是二进制的文件，需要通过：

jhat dumpFile.bin，然后在浏览器地址：http://localhost:7000/即可查看应用程序的内存信息

三：查看应用程序GC信息：

参考资料（http://www.cnblogs.com/alipayhutu/archive/2012/08/20/2647353.html）

执行命令：

jstat -gc 6464 3000

可以每隔三秒显示一次应用程序的GC信息