Separate logging for JPMS module/layer

[Luke Hutchison]

Thanks David for the detailed response!

On Mon, Oct 8, 2018 at 7:27 AM David Lloyd <david.lloyd at redhat.com> wrote:

> I think it's pretty reasonable to
> document that user programs that wish to have context-sensitive
> loggers should grant the "getStackWalkerWithClassReference"
> RuntimePermission to the logging JAR/module.


I looked for documentation on how to grant runtime permissions for a
specific module via the commandline or in a policy file, but I couldn't
figure out how to do this. The closest I found was "grant codeBase <URL>"
-- is this the right mechanism, used with the module location URL?


> I think a single clear
> behavior plus a documentation note would result in a better user
> experience than falling back through multiple potentially differing
> behaviors based on run time factors which may not be immediately clear
> to the user.
>

You make good points about predictability and expectations, although in my
current implementation the series of fallbacks is mostly intended to
support both JDK 9+ and JDK 7/8. (I implemented the StackWalker code using
reflection so that the code can be compiled for JDK 7.) The last
`Exception#getStackTrace()` fallback is there in case the main mechanism
for JDK 9+ or 7/8 doesn't work due to a SecurityException, so maybe that's
the case that should be removed in favor of clear documentation about the
need for runtime permissions if a SecurityManager is installed.