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@ -31,12 +31,12 @@ JConsole（Java Monitoring and Management Console）是一款基于 JMX（Java M
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打开位于 bin 目录下的 `jconsole` 程序后，它会自动扫描当前主机上的所有 JVM 进程：
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jconsole-start.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jconsole-start.png"/> </div>
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选中需要监控的进程后，点击连接，即可进入监控界面。监控界面包含了 *概览*、*内存*、*线程*、*类*、*VM 概要*、*MBean* 六个选项卡。其中概览界面显示的是 *内存*、*线程*、*类* 等三个选项卡界面的概览信息，如下所示：
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jconsole-概览.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jconsole-概览.png"/> </div>
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@ -45,7 +45,7 @@ JConsole（Java Monitoring and Management Console）是一款基于 JMX（Java M
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jconsole-内存.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jconsole-内存.png"/> </div>
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@ -54,14 +54,14 @@ JConsole（Java Monitoring and Management Console）是一款基于 JMX（Java M
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jconsole-检测死锁.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jconsole-检测死锁.png"/> </div>
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点击死锁选项卡则可以看到造成死锁的线程：
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jconsole-死锁.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jconsole-死锁.png"/> </div>
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@ -70,7 +70,7 @@ JConsole（Java Monitoring and Management Console）是一款基于 JMX（Java M
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jconsole-概要.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jconsole-概要.png"/> </div>
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@ -91,7 +91,7 @@ VisualVM（All-in-One Java Troubleshooting Tool）是 Oracle 提供的功能最
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打开位于 bin 目录下的 `jvisualvm` 程序， 它会自动扫描当前主机上的所有 JVM 进程：
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jvisual.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jvisual.png"/> </div>
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@ -100,7 +100,7 @@ VisualVM（All-in-One Java Troubleshooting Tool）是 Oracle 提供的功能最
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jvisual-监视.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jvisual-监视.png"/> </div>
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@ -111,7 +111,7 @@ VisualVM（All-in-One Java Troubleshooting Tool）是 Oracle 提供的功能最
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jvisual-堆dump.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jvisual-堆dump.png"/> </div>
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@ -120,7 +120,7 @@ VisualVM（All-in-One Java Troubleshooting Tool）是 Oracle 提供的功能最
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在线程界面可以查看所有线程的状态，如果出现死锁，该界面还会进行提示：
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jvisual-线程.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jvisual-线程.png"/> </div>
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@ -129,7 +129,7 @@ VisualVM（All-in-One Java Troubleshooting Tool）是 Oracle 提供的功能最
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jvisual-dump.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jvisual-dump.png"/> </div>
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@ -138,7 +138,7 @@ VisualVM（All-in-One Java Troubleshooting Tool）是 Oracle 提供的功能最
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在 Profiler 界面，可以进行 CPU 和 内存的性能分析。要开始性能分析，需要先选择 **CPU** 或 **内存** 按钮中的一个，VisualVM 将会开始记录应用程序执行过的所有方法：如果是进行的是 CPU 执行时间分析，将会统计每个方法的执行次数、执行耗时；如果是内存分析，则会统计每个方法关联的对象数以及这些对象所占的空间。想要结束性能分析，点击停止按钮即可：
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jvisual-性能分析.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jvisual-性能分析.png"/> </div>
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@ -147,7 +147,7 @@ VisualVM（All-in-One Java Troubleshooting Tool）是 Oracle 提供的功能最
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Visual GC 面板默认是不显示的，需要通过插件进行扩展。它会实时监控虚拟机的状态，在功能上类似于 jstat 命令：
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jvisual-gc.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jvisual-gc.png"/> </div>
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@ -156,7 +156,7 @@ Visual GC 面板默认是不显示的，需要通过插件进行扩展。它会
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在主界面，点击 **工具 => 插件** ，可以打开插件面板。右击插件选项或者点击安装按钮即可完成对应插件的安装：
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jvisual-插件安装.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jvisual-插件安装.png"/> </div>
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@ -165,7 +165,7 @@ Visual GC 面板默认是不显示的，需要通过插件进行扩展。它会
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jvisual-插件中心.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jvisual-插件中心.png"/> </div>
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@ -174,7 +174,7 @@ Visual GC 面板默认是不显示的，需要通过插件进行扩展。它会
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jvisual-配置插件中心.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jvisual-配置插件中心.png"/> </div>
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@ -232,7 +232,7 @@ chown root:root /usr/local/jmxremote.password
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之后在使用 VisualVM 进行远程连接时，配置如下：
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jvisual-连接远程主机.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jvisual-连接远程主机.png"/> </div>
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需要注意的是这里的端口号是配置的 `Dcom.sun.management.jmxremote.port` 的值，而不是 Java 程序的端口号。连接完成后，即可查看到对应进程的监控状态。
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@ -22,7 +22,7 @@
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jps（JVM Process Status Tool）用于列出正在运行的虚拟机进程的主类名称和 LVMID（Local Virtual Machine Identifier，本地虚拟机唯一标识），这里得到的 LVMID 是进行后续其它查询的基础。示例如下：
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```shell
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C:\Users>jps
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C:/Users>jps
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10848 Main
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14560 Jps
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7040 Launcher
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@ -65,7 +65,7 @@ jstat -<option> [-t] [-h<lines>] <vmid> [<interval> [<count>]]
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jstat -gc 9492 3s 5 # 每3s输出一次，一共输出5次
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```
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jstat_gc.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jstat_gc.png"/> </div>
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输出信息中各个参数含义分别如下：
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@ -115,7 +115,7 @@ jinfo -flags 13604
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jinfo -flag CMSInitiatingOccupancyFraction 13604
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```
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jinfo.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jinfo.png"/> </div>
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@ -145,7 +145,7 @@ jmap [option] <pid>
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jmap -dump:format=b,file=test.bin 3260
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```
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jmap.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jmap.png"/> </div>
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@ -170,22 +170,22 @@ public class StackOverFlowTest {
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其最终会抛出 `java.lang.OutOfMemoryError: Java heap space` 异常，意味着在 JVM 堆上发生了内存溢出。在程序运行期间，我们可以使用上面的 jmap 命令生成堆转储快照，并使用 jhat 命令进行分析：
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jhat.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jhat.png"/> </div>
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jhat 命令最终的分析结果会以网页的方式进行提供，端口为 7000，界面如下：
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jhat_web.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jhat_web.png"/> </div>
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jhat 分析的结果并不够直观，因此我们还可以借助第三方工具来分析堆转储快照，这里以 JProfiler 为例，该软件可以直接从[官网](https://www.ej-technologies.com/products/jprofiler/overview.htm)下载并安装，安装完成后，点击 `session` 选项卡，并使用 `Open Snapshot` 打开 jmap 命令生成的堆转储快照：
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jprofiler-1.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jprofiler-1.png"/> </div>
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之后程序会自动进行分析，分析结果如下：
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jprofiler-2.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jprofiler-2.png"/> </div>
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通过以上可视化的统计结果，我们就可以很快定位到导致内存溢出的原因。
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@ -250,7 +250,7 @@ jstack 8112
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输出结果如下：
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures\jstack.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/Full-Stack-Notes/raw/master/pictures/jstack.png"/> </div>
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从输出中结果中可以看出，出现了一个死锁，该死锁由线程 Thread-0 和 Thread-1 导致，原因是 Thread-0 锁住了对象 `<0x00000000d6d8d610>` ，并尝试获取 `<0x00000000d6d8d640>` 对象的锁；但是 Thread-0 却恰恰相反，锁住了对象 `<0x00000000d6d8d640>` ，并尝试获取 `<0x00000000d6d8d610>` 对象的锁，由此导致死锁。
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