Callback method parameter annotation @ReturnValue

Callback parameter annotated with @ReturnValue provides the instrumented method's return value.

In which callbacks can be used

Parameter annotated with @ReturnValue can be used in only in onReturn() and onExit().

Declaration type

Parameter annotated with @ReturnValue can be declared as a reference type or as a primitive type.

If the callback parameter is declared as java.lang.Object, it will be assigned with object reference as is if the actual parameter type is a reference type, or with a boxed value if the actual parameter type is primitive.

If the callback parameter is declared as some reference type other than java.lang.Object, it will be assigned with the actual method parameter value only if it is declared as strictly the same type. Otherwise, the callback parameter value will be null.

If the callback parameter is declared as a primitive type, it will be assigned with the actual method parameter value only if it is declared as strictly the same type. Otherwise, it will be assigned with 0; no type conversions will be performed. For example, int will not be cast to long.

Type of callback parameter annotated with @ReturnValue	Actual instrumented method return value type	Resulting value of the callback parameter
java.lang.Object	any reference type	the value as is
	any primitive type	a boxed value
	void	null
some reference type T1 other than java.lang.Object	same reference type T1	the value as is
	any reference or primitive type T2 != T1	null
	void	null
some primitive type T1	same primitive type T1	the value as is
	any reference or primitive type T2 != T1	0
	void	0

Note: The type matching rules for @ReturnValue are similar to ones for @Param and differ from the rules for @This