mirror of https://github.com/alibaba/arthas.git
You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
42 lines
3.1 KiB
Markdown
42 lines
3.1 KiB
Markdown
3 years ago
|
# Fundamental Fields in Expressions
|
||
|
|
|
||
|
|
There is a very fundamental class `Advice` for the expressions used in filtering, tracing or monitoring and other aspects in commands.
|
||
|
|
|
||
|
|
```java
|
||
|
|
public class Advice {
|
||
|
|
|
||
|
|
private final ClassLoader loader;
|
||
|
|
private final Class<?> clazz;
|
||
|
|
private final ArthasMethod method;
|
||
|
|
private final Object target;
|
||
|
|
private final Object[] params;
|
||
|
|
private final Object returnObj;
|
||
|
|
private final Throwable throwExp;
|
||
|
|
private final boolean isBefore;
|
||
|
|
private final boolean isThrow;
|
||
|
|
private final boolean isReturn;
|
||
|
|
|
||
|
|
// getter/setter
|
||
|
|
}
|
||
|
|
```
|
||
|
|
|
||
|
|
Description for the variables in the class `Advice`:
|
||
|
|
|
||
|
|
| Name | Specification |
|
||
|
|
| --------: | :------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
|
||
|
|
| loader | the class loader for the current called class |
|
||
|
|
| clazz | the reference to the current called class |
|
||
|
|
| method | the reference to the current called method |
|
||
|
|
| target | the instance of the current called class |
|
||
|
|
| params | the parameters for the current call, which is an array (when there's no parameter, it will be an empty array) |
|
||
|
|
| returnObj | the return value from the current call - only available when the method call returns normally (`isReturn==true`), and `null` is for `void` return value |
|
||
|
|
| throwExp | the exceptions thrown from the current call - only available when the method call throws exception (`isThrow==true`) |
|
||
|
|
| isBefore | flag to indicate the method is about to execute. `isBefore==true` but `isThrow==false` and `isReturn==false` since it's no way to know how the method call will end |
|
||
|
|
| isThrow | flag to indicate the method call ends with exception thrown |
|
||
|
|
| isReturn | flag to indicate the method call ends normally without exception thrown |
|
||
|
|
|
||
|
|
All variables listed above can be used directly in the [OGNL expression](https://commons.apache.org/proper/commons-ognl/language-guide.html). The command will not execute and exit if there's illegal OGNL grammar or unexpected variable in the expression.
|
||
|
|
|
||
|
|
- [typical use cases](https://github.com/alibaba/arthas/issues/71);
|
||
|
|
- [OGNL language guide](https://commons.apache.org/proper/commons-ognl/language-guide.html).
|