+
+
+
+
+
+
+
+ Critical 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
+}
+| Name | +Specification | +
|---|---|
| loader | +class loader of the class | +
| clazz | +the reference of the class | +
| method | +the reflective reference of the method | +
| target | +the instance of the class | +
| params | +the parameters of the method, which is an array (when there is no argument in the method, it will be an empty array) | +
| returnObj | +the return value of the method - only when isReturn==true, it's a valid result but if the return value is void then it will be a null |
+
| throwExp | +the exceptions thrown by the method invoking - only when isThrow==true, it's a valid thrown exception |
+
| isBefore | +assistant checking flag used in before-watching point and at this very moment: isBefore==true, isThrow==false and isReturn==false since it's before we invoke the method |
+
| isThrow | +assistant checking flag: whether the current method invoking ends with exceptions | +
| isReturn | +assistant checking flag: whether the method invoking exits normally without exceptions | +
F.Y.I
+-
+
- all the fields mentioned in the table above can be used directly in the
expressions;
+ - if the expressions are invalid OGNL, the command will be cancelled automatically with hints to correct the expressions; +
- typical use cases; +
- OGNL official usage guide. +
