java堆栈信息查看，以及JVM性能查看工具-jconsole+jmap

java-core  P487 P515

chapter11，主要讲java的异常，里面很多内容收获良多，之前一直没注意过的。

一，Throwable类获得StackTraceElement ，可进行堆栈跟踪，用法如下：

Throwable t = new Throwable();
StackTraceElement [] frames = t.getStackTrace();
for(StackTraceElement frame :frames)
 analyze frame

Map<Thread,StackTraceElement[] map>=Thread.getAllStackTraces();
for(Thread t :map.keySet()){
  StackTraceElement[] frames k= map.get(t);
  analyze frames
}

示例:

public class TestHeap {
    public static void main(String[]args){
        Throwable t = new Throwable();
        StringWriter out = new StringWriter();
        t.printStackTrace(new PrintWriter(out));
        String description = out.toString();
        System.out.println(description);
        System.out.println("——————分割线——————");
        StackTraceElement[]frames = t.getStackTrace();
        for(StackTraceElement frame:frames){
            System.out.println(frame);
        }
        System.out.println("——————分割线——————");
        Map<Thread,StackTraceElement[]> map = Thread.getAllStackTraces();
        for(Thread t1:map.keySet()){
            StackTraceElement []fram=map.get(t1);
            for(StackTraceElement element :fram){
                System.out.println("--- "+element.getClassName()+"--- "
                        +element.getClass().getName()+" ---"+element.getFileName()
                        +",--- "+element.getMethodName()+",--- "+element.getLineNumber());
            }

        }
    }
}

　　

输出结果：

java.lang.Throwable
	at enums.TestHeap.main(TestHeap.java:9)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

——————分割线——————
enums.TestHeap.main(TestHeap.java:9)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:498)
com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
——————分割线——————
--- java.lang.ClassLoader$NativeLibrary--- java.lang.StackTraceElement ---ClassLoader.java,--- load,--- -2
--- java.lang.ClassLoader--- java.lang.StackTraceElement ---ClassLoader.java,--- loadLibrary0,--- 1941
--- java.lang.ClassLoader--- java.lang.StackTraceElement ---ClassLoader.java,--- loadLibrary,--- 1845
--- java.lang.Runtime--- java.lang.StackTraceElement ---Runtime.java,--- loadLibrary0,--- 870
--- java.lang.System--- java.lang.StackTraceElement ---System.java,--- loadLibrary,--- 1122
--- java.net.AbstractPlainSocketImpl$1--- java.lang.StackTraceElement ---AbstractPlainSocketImpl.java,--- run,--- 84
--- java.net.AbstractPlainSocketImpl$1--- java.lang.StackTraceElement ---AbstractPlainSocketImpl.java,--- run,--- 82
--- java.security.AccessController--- java.lang.StackTraceElement ---AccessController.java,--- doPrivileged,--- -2
--- java.net.AbstractPlainSocketImpl--- java.lang.StackTraceElement ---AbstractPlainSocketImpl.java,--- <clinit>,--- 81
--- java.net.ServerSocket--- java.lang.StackTraceElement ---ServerSocket.java,--- setImpl,--- 288
--- java.net.ServerSocket--- java.lang.StackTraceElement ---ServerSocket.java,--- <init>,--- 230
--- java.net.ServerSocket--- java.lang.StackTraceElement ---ServerSocket.java,--- <init>,--- 128
--- com.intellij.rt.execution.application.AppMain$1--- java.lang.StackTraceElement ---AppMain.java,--- run,--- 77
--- java.lang.Thread--- java.lang.StackTraceElement ---Thread.java,--- run,--- 748
--- java.lang.Thread--- java.lang.StackTraceElement ---Thread.java,--- dumpThreads,--- -2
--- java.lang.Thread--- java.lang.StackTraceElement ---Thread.java,--- getAllStackTraces,--- 1610
--- enums.TestHeap--- java.lang.StackTraceElement ---TestHeap.java,--- main,--- 20
--- sun.reflect.NativeMethodAccessorImpl--- java.lang.StackTraceElement ---NativeMethodAccessorImpl.java,--- invoke0,--- -2
--- sun.reflect.NativeMethodAccessorImpl--- java.lang.StackTraceElement ---NativeMethodAccessorImpl.java,--- invoke,--- 62
--- sun.reflect.DelegatingMethodAccessorImpl--- java.lang.StackTraceElement ---DelegatingMethodAccessorImpl.java,--- invoke,--- 43
--- java.lang.reflect.Method--- java.lang.StackTraceElement ---Method.java,--- invoke,--- 498
--- com.intellij.rt.execution.application.AppMain--- java.lang.StackTraceElement ---AppMain.java,--- main,--- 147
--- java.lang.Object--- java.lang.StackTraceElement ---Object.java,--- wait,--- -2
--- java.lang.ref.ReferenceQueue--- java.lang.StackTraceElement ---ReferenceQueue.java,--- remove,--- 143
--- java.lang.ref.ReferenceQueue--- java.lang.StackTraceElement ---ReferenceQueue.java,--- remove,--- 164
--- java.lang.ref.Finalizer$FinalizerThread--- java.lang.StackTraceElement ---Finalizer.java,--- run,--- 209
--- java.lang.Object--- java.lang.StackTraceElement ---Object.java,--- wait,--- -2
--- java.lang.Object--- java.lang.StackTraceElement ---Object.java,--- wait,--- 502
--- java.lang.ref.Reference--- java.lang.StackTraceElement ---Reference.java,--- tryHandlePending,--- 191
--- java.lang.ref.Reference$ReferenceHandler--- java.lang.StackTraceElement ---Reference.java,--- run,--- 153

Process finished with exit code 0

　　

二，jconsole和jmap

之前有了解过java的JVM性能监控工具，但是没有具体执行过，只是有个很模糊的概念。

　　jconsole原理：

　　java允许虚拟机中的代理装置跟踪内存消耗，线程使用，类加载等情况。jconsole就是一个展示这种功能的例子：用于显示虚拟机性能的统计结果。

　　jconsole 用法

>cmd
>jconsole
>jconsole pid

　　jconsole页面

　　jmap

　　可以使用jmap获得一个堆的存储，其中显示了堆中的每个对象，使用如下：

jmap pid

　　

　　结果如下

C:\Users\user>jmap 3128
Attaching to process ID 3128, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.144-b01
0x0000000053040000      36K     C:\Program Files\Java\jdk1.8.0_144\jre\bin\attach.dll
0x0000000053050000      840K    C:\Program Files\Java\jdk1.8.0_144\bin\MSVCR100.dll
0x0000000053130000      188K    C:\Program Files\Java\jdk1.8.0_144\bin\jli.dll
0x0000000053160000      840K    C:\Program Files\Java\jdk1.8.0_144\jre\bin\msvcr100.dll
0x0000000053240000      168K    C:\Program Files\Java\jdk1.8.0_144\jre\bin\dcpr.dll
0x00000000532c0000      264K    C:\Program Files\Java\jdk1.8.0_144\jre\bin\t2k.dll
0x0000000053390000      52K     C:\Program Files\Java\jdk1.8.0_144\jre\bin\management.dll
0x00000000533a0000      68K     C:\Program Files\Java\jdk1.8.0_144\jre\bin\nio.dll
0x00000000533c0000      104K    C:\Program Files\Java\jdk1.8.0_144\jre\bin\net.dll
0x00000000533e0000      284K    C:\Program Files\Java\jdk1.8.0_144\jre\bin\fontmanager.dll
0x0000000053430000      1632K   C:\Program Files\Java\jdk1.8.0_144\jre\bin\awt.dll
0x00000000535d0000      88K     C:\Program Files\Java\jdk1.8.0_144\jre\bin\zip.dll
0x0000000053620000      164K    C:\Program Files\Java\jdk1.8.0_144\jre\bin\java.dll
0x0000000053650000      60K     C:\Program Files\Java\jdk1.8.0_144\jre\bin\verify.dll
0x0000000053740000      8820K   C:\Program Files\Java\jdk1.8.0_144\jre\bin\server\jvm.dll
0x0000000180000000      804K    c:\program files (x86)\kingsoft\kingsoft antivirus\kwsui64.dll
0x00007ff6c24d0000      28K     C:\Program Files\Java\jdk1.8.0_144\bin\jconsole.exe

　　

另外，还有一个收费的工具，比较有名也直接，叫jprofiler。

可参考：

https://www.cnblogs.com/AmilyWilly/p/7272160.html?utm_source=itdadao&utm_medium=referral