java自带命令行工具(jmap,jhat,jinfo) 推荐

（1）JMAP

1.作用
打印进程，core文件,和远程进程的共享对象存储map或堆存储器的详细信息。
2.使用

jmap [ options ] pid
jmap [ options ] executable core
jmap [ options ] [ pid ] server-id@ ] remote-hostname-or-IP

如果指定的进程是在64位Java虚拟机（JVM）上运行，那么你可能需要指定-J-d64选项，例如：jmap -J-d64 -heap pid。
3.参数选项
3.1 <no option>
当不使用选项，该jmap命令打印共享对象映射
如

C:\Users\Administrator>jmap 9208
Attaching to process ID 9208, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.75-b04
0x00000000623c0000      8016K   D:\Java\jdk1.7.0_75\jre\bin\server\jvm.dll
0x0000000062ba0000      840K    D:\Java\jdk1.7.0_75\jre\bin\msvcr100.dll
0x0000000062cc0000      144K    D:\Java\jdk1.7.0_75\jre\bin\sunec.dll
0x0000000062cf0000      68K     D:\Java\jdk1.7.0_75\jre\bin\nio.dll
0x0000000062d10000      100K    D:\Java\jdk1.7.0_75\jre\bin\net.dll
0x0000000062d30000      160K    D:\Java\jdk1.7.0_75\jre\bin\java.dll
0x00000000634d0000      84K     D:\Java\jdk1.7.0_75\jre\bin\zip.dll
0x0000000065950000      44K     D:\Java\jdk1.7.0_75\jre\bin\sunmscapi.dll
0x0000000065960000      60K     D:\Java\jdk1.7.0_75\jre\bin\verify.dll
0x0000000065970000      44K     D:\Java\jdk1.7.0_75\jre\bin\management.dll
...

3.2
-dump:[live,] format=b, file=filename
转储Java堆hprof二进制格式。指定live,标识转储active状态的对象。生成的文件可以由jhat命令查看。

C:\Users\Administrator>jmap -dump:format=b,file=9208_0413.hprof 9208
Dumping heap to C:\Users\Administrator\9208_0413.hprof ...
Heap dump file created

3.3 -finalizerinfo
打印将要结束的对象的信息

C:\Users\Administrator>jmap -finalizerinfo  9208
Attaching to process ID 9208, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.75-b04
Number of objects pending for finalization: 0

3.4 -heap
打印垃圾收集和heap摘要信息，以及生成-wise 堆使用的堆摘要

C:\Users\Administrator>jmap -heap 9208
Attaching to process ID 9208, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.75-b04

using thread-local object allocation.
Parallel GC with 4 thread(s)

Heap Configuration:
MinHeapFreeRatio = 0
MaxHeapFreeRatio = 100
MaxHeapSize      = 2124414976 (2026.0MB)
NewSize          = 1310720 (1.25MB)
MaxNewSize       = 17592186044415 MB
OldSize          = 5439488 (5.1875MB)
NewRatio         = 2
SurvivorRatio    = 8
PermSize         = 21757952 (20.75MB)
MaxPermSize      = 85983232 (82.0MB)
G1HeapRegionSize = 0 (0.0MB)

Heap Usage:
PS Young Generation
Eden Space:
capacity = 68157440 (65.0MB)
used     = 16646688 (15.875518798828125MB)
free     = 51510752 (49.124481201171875MB)
24.423875075120193% used
From Space:
capacity = 5242880 (5.0MB)
used     = 5228248 (4.986045837402344MB)
free     = 14632 (0.01395416259765625MB)
99.72091674804688% used
To Space:
capacity = 15728640 (15.0MB)
used     = 0 (0.0MB)
free     = 15728640 (15.0MB)
0.0% used
PS Old Generation
capacity = 88080384 (84.0MB)
used     = 27239848 (25.977943420410156MB)
free     = 60840536 (58.022056579589844MB)
30.9261231195359% used
PS Perm Generation
capacity = 22020096 (21.0MB)
used     = 15369592 (14.657585144042969MB)
free     = 6650504 (6.342414855957031MB)
69.7980244954427% used

10057 interned Strings occupying 867832 bytes.

3.5 -histo[:live]
打印堆的直方图

num     #instances         #bytes  class name
----------------------------------------------
...

877:             1             32  [Lcom.sun.jndi.ldap.pool.Pool;
878:             2             32  com.sun.org.apache.xerces.internal.impl.dv.dtd.ENTITYDatatypeValidator
879:             2             32  java.lang.Shutdown$Lock
880:             1             32  org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler
881:             2             32  com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$DTDDriver
882:             1             32  java.lang.reflect.WeakCache$CacheKey
883:             1             32  java.text.FieldPosition
884:             1             32  java.util.concurrent.atomic.AtomicReferenceFieldUpdater$AtomicReferenceFieldUpdaterImpl
885:             2             32  sun.security.x509.CertificateVersion
886:             2             32  [Lorg.apache.catalina.deploy.ContextEnvironment;
887:             1             32  [Lorg.apache.tomcat.util.net.AbstractEndpoint$Acceptor$AcceptorState;
888:             1             32  sun.nio.cs.StandardCharsets
...

3.6 -clstats
java 堆的wise统计。1.7.0_75不支持该项
（2）jhat

2.1作用
分析Java堆。该jhat命令解析Java堆转储文件并启动Web服务器。jhat命令可以让你浏览堆转储。支持OQL语法。
2.2使用
jhat [ options ] heap-dump-file

2.3参数说明

1.-stack false|true

关闭跟踪对象分配调用堆栈。默认值是true。
-refs false|true
关闭对象的引用的跟踪。默认为true。
-port port-number
设置端口的jhatHTTP服务器。默认值是7000。
-exclude exclude-file
指定列出了应当从可及的对象查询排除数据成员的文件

-baseline exclude-file
指定基准堆转储。在具有相同的对象ID两个堆转储对象被标记为不是新对象。这是用于比较两个不同的堆转储有用。
-debug int
0级表示没有调试输出

C:\Users\Administrator>jhat -port 8000  9208_0413.hprof
Reading from 9208_0413.hprof...
Dump file created Thu Apr 13 21:18:58 CST 2017
Snapshot read, resolving...
Resolving 389761 objects...
Chasing references, expect 77 dots..........................................................................
Eliminating duplicate references............................................................................
Snapshot resolved.
Started HTTP server on port 8000
Server is ready.

接下来，就可以通过浏览器访问查看。http://localhost:8000/。
(3)jinfo
3.1作用
生成的配置信息。如果指定的进程是在64位JVM上运行，那么你可能需要指定-J-d64选项
3.2使用

jinfo [ option ] pid
jinfo [ option ] executable core
jinfo [ option ] [ servier-id ] remote-hostname-or-IP

3.3选项参数

no-option：既打印命令行标志和系统属性键值对。
-flag name
打印名和指定的命令行标志的值。
-flag [+|-]name
开启或禁止指定的布尔命令行标志。
-flag name=value
设置指定的命令行标志为指定值。

-flags
打印命令行标志传递给JVM。
-sysprops
打印Java系统属性键值对。

打印进程的命令行参数

C:\Users\Administrator>jinfo -flags 9208
Attaching to process ID 9208, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.75-b04

-Djava.util.logging.config.file=D:\apache-tomcat-7.0.67\conf\logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager
-Djava.endorsed.dirs=D:\apache-tomcat-7.0.67\endorsed -Dcatalina.base=D:\apache-tomcat-7.0.67 -Dcatalina.home=D:\apache-tomcat-7.0.67 -Djava.io.
tmpdir=D:\apache-tomcat-7.0.67\temp
#在catalina.sh中可以找到设置的地方

打印参数值

#值类型参数
C:\Users\Administrator>jinfo -flag NewSize 9208
-XX:NewSize=1310720

#开关类型参数
C:\Users\Administrator>jinfo -flag PrintGC 9208
-XX:-PrintGC

C:\Users\Administrator>jinfo -flag Xmn 9208
no such flag 'Xmn'

可以总结出：-xms,-xmn系列参数不能通过jinfo指定或打印；jinfo命令作用于-XX:***格式的参数。
设置参数值

C:\Users\Administrator>jinfo -flag PrintGC 9208
-XX:-PrintGC

C:\Users\Administrator>jinfo -flag +PrintGC 9208

C:\Users\Administrator>jinfo -flag PrintGC 9208
-XX:+PrintGC
//2 windows环境总是失败

C:\Users\Administrator>jinfo -flag PermSize=21750000 9208
Exception in thread "main" java.io.IOException: Command failed in target VM
at sun.tools.attach.WindowsVirtualMachine.execute(WindowsVirtualMachine.java:112)
at sun.tools.attach.HotSpotVirtualMachine.executeCommand(HotSpotVirtualMachine.java:217)
at sun.tools.attach.HotSpotVirtualMachine.setFlag(HotSpotVirtualMachine.java:190)
at sun.tools.jinfo.JInfo.flag(JInfo.java:123)
at sun.tools.jinfo.JInfo.main(JInfo.java:76)

http://docs.oracle.com/javase/8/docs/technotes/tools/unix/jhat.html
http://docs.oracle.com/javase/8/docs/technotes/tools/unix/jinfo.html
http://docs.oracle.com/javase/8/docs/technotes/tools/unix/jmap.html