Separate logging for JPMS module/layer

[David Lloyd]

On Mon, Oct 8, 2018 at 9:38 AM Luke Hutchison <luke.hutch at gmail.com> wrote:
> On Mon, Oct 8, 2018 at 7:27 AM David Lloyd <david.lloyd at redhat.com> wrote:
>> 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.

You might want to consider doing a multi-release JAR instead.  Your
base image could support Java 7, and there could be a Java 9-specific
layer which implements just the StackWalker stuff, overlaying the
legacy code.

The reflection approach works in a pinch, but it gets unwieldy pretty
quickly as the differences mount.
-- 
- DML