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95 lines
3.5 KiB
Plaintext
95 lines
3.5 KiB
Plaintext
ognl
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===
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[`ognl` online tutorial](https://arthas.aliyun.com/doc/arthas-tutorials?language=en&id=command-ognl)
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> Execute ognl expression.
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Since 3.0.5.
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### Parameters
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|Name|Specification|
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|---:|:---|
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|*express*|expression to be executed|
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|`[c:]`| The hashcode of the ClassLoader that executes the expression, default ClassLoader is SystemClassLoader. |
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|`[classLoaderClass:]`| The class name of the ClassLoader that executes the expression. |
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|[x]|Expand level of object (1 by default).|
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### Usage
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* [Special usages](https://github.com/alibaba/arthas/issues/71)
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* [OGNL official guide](https://commons.apache.org/proper/commons-ognl/language-guide.html)
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Call static method:
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```bash
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$ ognl '@java.lang.System@out.println("hello")'
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null
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```
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Get static field:
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```bash
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$ ognl '@demo.MathGame@random'
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@Random[
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serialVersionUID=@Long[3905348978240129619],
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seed=@AtomicLong[125451474443703],
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multiplier=@Long[25214903917],
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addend=@Long[11],
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mask=@Long[281474976710655],
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DOUBLE_UNIT=@Double[1.1102230246251565E-16],
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BadBound=@String[bound must be positive],
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BadRange=@String[bound must be greater than origin],
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BadSize=@String[size must be non-negative],
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seedUniquifier=@AtomicLong[-3282039941672302964],
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nextNextGaussian=@Double[0.0],
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haveNextNextGaussian=@Boolean[false],
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serialPersistentFields=@ObjectStreamField[][isEmpty=false;size=3],
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unsafe=@Unsafe[sun.misc.Unsafe@28ea5898],
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seedOffset=@Long[24],
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]
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```
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Specify ClassLoader by hashcode:
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```bash
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$ classloader -t
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+-BootstrapClassLoader
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+-jdk.internal.loader.ClassLoaders$PlatformClassLoader@301ec38b
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+-com.taobao.arthas.agent.ArthasClassloader@472067c7
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+-jdk.internal.loader.ClassLoaders$AppClassLoader@4b85612c
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+-org.springframework.boot.loader.LaunchedURLClassLoader@7f9a81e8
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$ ognl -c 7f9a81e8 @org.springframework.boot.SpringApplication@logger
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@Slf4jLocationAwareLog[
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FQCN=@String[org.apache.commons.logging.LogAdapter$Slf4jLocationAwareLog],
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name=@String[org.springframework.boot.SpringApplication],
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logger=@Logger[Logger[org.springframework.boot.SpringApplication]],
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]
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$
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```
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Note that the hashcode changes, you need to check the current ClassLoader information first, and extract the hashcode corresponding to the ClassLoader.
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For ClassLoader with only unique instance, it can be specified by class name, which is more convenient to use:
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```bash
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$ ognl --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader @org.springframework.boot.SpringApplication@logger
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@Slf4jLocationAwareLog[
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FQCN=@String[org.apache.commons.logging.LogAdapter$Slf4jLocationAwareLog],
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name=@String[org.springframework.boot.SpringApplication],
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logger=@Logger[Logger[org.springframework.boot.SpringApplication]],
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]
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```
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Execute a multi-line expression, and return a list:
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```bash
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$ ognl '#value1=@System@getProperty("java.home"), #value2=@System@getProperty("java.runtime.name"), {#value1, #value2}'
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@ArrayList[
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@String[/opt/java/8.0.181-zulu/jre],
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@String[OpenJDK Runtime Environment],
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]
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``` |