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.
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. The command will not execute and exit if there's illegal OGNL grammar or unexpected variable in the expression.