Review Request: JDK-8157464: StackWalker.getCallerClass() is not

[Mandy Chung]

Webrev:
 http://cr.openjdk.java.net/~mchung/jdk9/webrevs/8157464/webrev.01

This revises the proposal posted some time ago [1].

StackWalker::getCallerClass is a convenient method to find the caller class. It will return the invoker of the MethodHandle and java.lang.reflect.Method for the method calling StackWalker::getCallerClass, as it’s currently specified.

This issue is related to MethodHandle for @CallerSensitive method.  It behaves as if the caller is the lookup class and in the current implementation, the actual caller class is not the lookup class but a generated class.

One intended usage of StackWalker::getCallerClass is to be called by library code acting as an agent that calls @CallerSensitive method on behalf of the true caller and typically it will call an appropriate method with the appropriate parameter (e.g. ResourceBundle.getBundle(String, ClassLoader).

Given that StackWalker::getCallerClass is not expected to be used by any @CS method, this patch proposes to catch and throw an exception if StackWalker::getCallerClass is called by a @CS method.  This will allow time to revisit this when such need is identified.

thanks
Mandy
[1] http://mail.openjdk.java.net/pipermail/core-libs-dev/2016-July/042345.html