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arthas/_sources/ognl.md.txt

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ognl
===
> 执行ognl表达式
从3.0.5版本增加
### 参数说明
|参数名称|参数说明|
|---:|:---|
|*express*|执行的表达式|
|`[c:]`|执行表达式的 ClassLoader 的 hashcode默认值是SystemClassLoader|
|[x]|结果对象的展开层次默认值1|
### 使用参考
* OGNL特殊用法请参考[https://github.com/alibaba/arthas/issues/71](https://github.com/alibaba/arthas/issues/71)
* OGNL表达式官方指南[https://commons.apache.org/proper/commons-ognl/language-guide.html](https://commons.apache.org/proper/commons-ognl/language-guide.html)
调用静态函数:
```bash
$ ognl '@java.lang.System@out.println("hello")'
null
```
获取静态类的静态字段:
```bash
$ ognl '@demo.MathGame@random'
@Random[
serialVersionUID=@Long[3905348978240129619],
seed=@AtomicLong[125451474443703],
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@28ea5898],
seedOffset=@Long[24],
]
```
执行多行表达式赋值给临时变量返回一个List
```bash
$ ognl '#value1=@System@getProperty("java.home"), #value2=@System@getProperty("java.runtime.name"), {#value1, #value2}'
@ArrayList[
@String[/opt/java/8.0.181-zulu/jre],
@String[OpenJDK Runtime Environment],
]
```