Table of Contents

getstatic

getstatic online tutorial

Usage

• It is recommended to use the [OGNL] (ognl.md) command, which will be more flexible.

Check the static fields of classes conveniently, the usage is getstatic class_name field_name.

$ getstatic demo.MathGame random
field: random
@Random[
    serialVersionUID=@Long[3905348978240129619],
    seed=@AtomicLong[120955813885284],
    multiplier=@Long[25214903917],
    addend=@Long[11],
    mask=@Long[281474976710655],
    DOUBLE_UNIT=@Double[1.1102230246251565E-16],
    BadBound=@String[bound must be positive],
    BadRange=@String[bound must be greater than origin],
    BadSize=@String[size must be non-negative],
    seedUniquifier=@AtomicLong[-3282039941672302964],
    nextNextGaussian=@Double[0.0],
    haveNextNextGaussian=@Boolean[false],
    serialPersistentFields=@ObjectStreamField[][isEmpty=false;size=3],
    unsafe=@Unsafe[sun.misc.Unsafe@2eaa1027],
    seedOffset=@Long[24],
]

• Specify classLoader

Note that the hashcode changes, you need to check the current ClassLoader information first, and extract the hashcode corresponding to the ClassLoader using sc -d <ClassName>.

if you use-c, you have to manually type hashcode by -c <hashcode>.

$ getstatic -c 3d4eac69 demo.MathGame random

For classloader with only one instance, it can be specified by --classLoaderClass using class name, which is more convenient to use.

getstatic --classLoaderClass demo.MathGame random

• PS: Here the classLoaderClass in java 8 is sun.misc.Launcher$AppClassLoader, while in java 11 it's jdk.internal.loader.ClassLoaders$AppClassLoader. Currently katacoda using java 8.

The value of --classloaderclass is the class name of classloader. It can only work when it matches a unique classloader instance. The purpose is to facilitate the input of general commands. However, -c <hashcode> is dynamic.

Tip: if the static field is a complex class, you can even use OGNL to traverse, filter and access the inner properties of this class.

• OGNL official guide
• Special usages

E.g. suppose n is a Map and its key is a Enum, then you can achieve this if you want to pick the key with a specific Enum value:

$ getstatic com.alibaba.arthas.Test n 'entrySet().iterator.{? #this.key.name()=="STOP"}'
field: n
@ArrayList[
    @Node[STOP=bbb],
]
Affect(row-cnt:1) cost in 68 ms.


$ getstatic com.alibaba.arthas.Test m 'entrySet().iterator.{? #this.key=="a"}'
field: m
@ArrayList[
    @Node[a=aaa],
]