1. dashboard—当前系统的实时数据面板
第二章节已说，这里不再赘述
2. thread—查看当前 JVM 的线程堆栈信息
第二章节已说，这里不再赘述
3. jvm—查看当前 JVM 的信息
jvm
4. sysprop—查看和修改JVM的系统属性
4.1 查看全部
$ sysprop
KEY VALUE
-------------------------------------------------------------------------------------------------------------------------------------
java.runtime.name Java(TM) SE Runtime Environment
sun.boot.library.path /Library/Java/JavaVirtualMachines/jdk1.8.0_51.jdk/Contents/Home/jre/lib
java.vm.version 25.51-b03
user.country.format CN
gopherProxySet false
java.vm.vendor Oracle Corporation
java.vendor.url http://java.oracle.com/
path.separator :
java.vm.name Java HotSpot(TM) 64-Bit Server VM
file.encoding.pkg sun.io
user.country US
sun.java.launcher SUN_STANDARD
sun.os.patch.level unknown
java.vm.specification.name Java Virtual Machine Specification
user.dir /private/var/tmp
java.runtime.version 1.8.0_51-b16
java.awt.graphicsenv sun.awt.CGraphicsEnvironment
java.endorsed.dirs /Library/Java/JavaVirtualMachines/jdk1.8.0_51.jdk/Contents/Home/jre/lib/endors
ed
os.arch x86_64
java.io.tmpdir /var/folders/2c/tbxwzs4s4sbcvh7frbcc7n000000gn/T/
line.separator
java.vm.specification.vendor Oracle Corporation
os.name Mac OS X
sun.jnu.encoding UTF-8
java.library.path /Users/wangtao/Library/Java/Extensions:/Library/Java/Extensions:/Network/Libra
ry/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java:.
sun.nio.ch.bugLevel
java.specification.name Java Platform API Specification
java.class.version 52.0
sun.management.compiler HotSpot 64-Bit Tiered Compilers
os.version 10.12.6
user.home /Users/wangtao
user.timezone Asia/Shanghai
java.awt.printerjob sun.lwawt.macosx.CPrinterJob
file.encoding UTF-8
java.specification.version 1.8
user.name wangtao
java.class.path .
java.vm.specification.version 1.8
sun.arch.data.model 64
java.home /Library/Java/JavaVirtualMachines/jdk1.8.0_51.jdk/Contents/Home/jre
sun.java.command Test
java.specification.vendor Oracle Corporation
user.language en
awt.toolkit sun.lwawt.macosx.LWCToolkit
java.vm.info mixed mode
java.version 1.8.0_51
java.ext.dirs /Users/wangtao/Library/Java/Extensions:/Library/Java/JavaVirtualMachines/jdk1.
8.0_51.jdk/Contents/Home/jre/lib/ext:/Library/Java/Extensions:/Network/Library
/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java
sun.boot.class.path /Library/Java/JavaVirtualMachines/jdk1.8.0_51.jdk/Contents/Home/jre/lib/resour
ces.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_51.jdk/Contents/Home/jre/li
b/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_51.jdk/Contents/Home/jre/l
ib/sunrsasign.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_51.jdk/Contents/H
ome/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_51.jdk/Content
s/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_51.jdk/Conte
nts/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_51.jd
k/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_51.
jdk/Contents/Home/jre/classes
java.vendor Oracle Corporation
file.separator /
java.vendor.url.bug http://bugreport.sun.com/bugreport/
sun.cpu.endian little
sun.io.unicode.encoding UnicodeBig
sun.cpu.isalist
4.2 查看指定属性
$ sysprop java.version
4.3 修改单个属性
-- 查看
$ sysprop user.country
user.country=US
-- 修改
$ sysprop user.country CN
Successfully changed the system property.
user.country=CN
5. sysenv—查看JVM的环境变量
5.1 查看全部环境变量
sysenv
5.2 查看指定环境变量
sysenv 环境变量KEY
如：sysenv JAVA_HOME
6. vmoption—查看和修改JVM里诊断相关的option
6.1 查看全部option
vmoption
6.2 查看指定option
vmoption key
如：vmoption MaxHeapFreeRatio
6.3 更新指定option
[arthas@56963]$ vmoption PrintGCDetails true
Successfully updated the vm option.
PrintGCDetails=true
7. perfcounter—查看当前 JVM 的Perf Counter信息使用参考
$ perfcounter
java.ci.totalTime 2325637411
java.cls.loadedClasses 3403
java.cls.sharedLoadedClasses 0
java.cls.sharedUnloadedClasses 0
java.cls.unloadedClasses 0
java.property.java.version 11.0.4
java.property.java.vm.info mixed mode
java.property.java.vm.name OpenJDK 64-Bit Server VM
...
可以用-d参数打印更多信息：
$ perfcounter -d
Name Variability Units Value
---------------------------------------------------------------------------------
java.ci.totalTime Monotonic Ticks 3242526906
java.cls.loadedClasses Monotonic Events 3404
java.cls.sharedLoadedClasses Monotonic Events 0
java.cls.sharedUnloadedClasses Monotonic Events 0
java.cls.unloadedClasses Monotonic Events 0
如果没有打印出信息，应用在启动时，加下面的参数：
--add-opens java.base/jdk.internal.perf=ALL-UNNAMED --add-exports java.base/jdk.internal.perf=ALL-UNNAMED
8. logger—查看和修改logger
8.1 查看所有logger信息
[arthas@2062]$ logger
name ROOT
class ch.qos.logback.classic.Logger
classLoader sun.misc.Launcher$AppClassLoader@2a139a55
classLoaderHash 2a139a55
level INFO
effectiveLevel INFO
additivity true
codeSource file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar
appenders name CONSOLE
class ch.qos.logback.core.ConsoleAppender
classLoader sun.misc.Launcher$AppClassLoader@2a139a55
classLoaderHash 2a139a55
target System.out
name APPLICATION
class ch.qos.logback.core.rolling.RollingFileAppender
classLoader sun.misc.Launcher$AppClassLoader@2a139a55
classLoaderHash 2a139a55
file app.log
name ASYNC
class ch.qos.logback.classic.AsyncAppender
classLoader sun.misc.Launcher$AppClassLoader@2a139a55
classLoaderHash 2a139a55
appenderRef [APPLICATION]
从appenders的信息里，可以看到
CONSOLElogger的target是System.outAPPLICATIONlogger是RollingFileAppender，它的file是app.logASYNC它的appenderRef是APPLICATION，即异步输出到文件里
8.2 查看指定logger
[arthas@2062]$ logger -n org.springframework.web
name org.springframework.web
class ch.qos.logback.classic.Logger
classLoader sun.misc.Launcher$AppClassLoader@2a139a55
classLoaderHash 2a139a55
level null
effectiveLevel INFO
additivity true
codeSource file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar
8.3 查看指定classloader的logger
其中，classloader为上述8.1或8.2中返回的
[arthas@2062]$ logger -c 2a139a55
name ROOT
class ch.qos.logback.classic.Logger
classLoader sun.misc.Launcher$AppClassLoader@2a139a55
classLoaderHash 2a139a55
level DEBUG
effectiveLevel DEBUG
additivity true
codeSource file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar
appenders name CONSOLE
class ch.qos.logback.core.ConsoleAppender
classLoader sun.misc.Launcher$AppClassLoader@2a139a55
classLoaderHash 2a139a55
target System.out
name APPLICATION
class ch.qos.logback.core.rolling.RollingFileAppender
classLoader sun.misc.Launcher$AppClassLoader@2a139a55
classLoaderHash 2a139a55
file app.log
name ASYNC
class ch.qos.logback.classic.AsyncAppender
classLoader sun.misc.Launcher$AppClassLoader@2a139a55
classLoaderHash 2a139a55
appenderRef [APPLICATION]
8.4 更新全局logger level
[arthas@2062]$ logger --name ROOT --level debug
update logger level success.
8.5 更新指定classloader logger level
默认情况下，logger命令会在SystemClassloader下执行，如果应用是传统的war应用，或者spring boot fat jar启动的应用，那么需要指定classloader。
可以先用 sc-dyourClassName 来查看具体的 classloader hashcode，然后在更新level时指定classloader：
[arthas@2062]$ logger -c 2a139a55 --name ROOT --level debug
8.6 查看没有appender的logger
默认情况下，logger命令只打印有appender的logger的信息。如果想查看没有appender的logger的信息，可以加上参数--include-no-appender。
注意，通常输出结果会很长
[arthas@2062]$ logger --include-no-appender
name ROOT
class ch.qos.logback.classic.Logger
classLoader sun.misc.Launcher$AppClassLoader@2a139a55
classLoaderHash 2a139a55
level DEBUG
effectiveLevel DEBUG
additivity true
codeSource file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar
appenders name CONSOLE
class ch.qos.logback.core.ConsoleAppender
classLoader sun.misc.Launcher$AppClassLoader@2a139a55
classLoaderHash 2a139a55
target System.out
name APPLICATION
class ch.qos.logback.core.rolling.RollingFileAppender
classLoader sun.misc.Launcher$AppClassLoader@2a139a55
classLoaderHash 2a139a55
file app.log
name ASYNC
class ch.qos.logback.classic.AsyncAppender
classLoader sun.misc.Launcher$AppClassLoader@2a139a55
classLoaderHash 2a139a55
appenderRef [APPLICATION]
name com
class ch.qos.logback.classic.Logger
classLoader sun.misc.Launcher$AppClassLoader@2a139a55
classLoaderHash 2a139a55
level null
effectiveLevel DEBUG
additivity true
codeSource file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar
name com.alibaba
class ch.qos.logback.classic.Logger
classLoader sun.misc.Launcher$AppClassLoader@2a139a55
classLoaderHash 2a139a55
level null
effectiveLevel DEBUG
additivity true
codeSource file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar
...
9. getstatic—查看类的静态属性
有需再更
10. ognl—执行ognl表达式
有需再更
11. mbean—查看 Mbean 的信息
有需再更
