JEP 220 questions

Martijn Verburg martijnverburg at
Thu Oct 30 18:58:22 UTC 2014

Hi Mark/All,

I've just had a read through JEP 220 and it made for a good read!  I do
have a couple of questions though. I apologise in advance if my archive
searching skills failed with regards to any duplicated questions.

1. The endorsed-standards override mechanism & The extension mechanism

>... "To help identify any existing uses of this mechanism we will modify
the compiler and the
>launcher to fail if this system property is set or if the lib/endorsed
directory exists"...

Are these tools intended to be released before Java 9/10 (e.g. Like jdeps)
to help developers prepare, or will it be a deprecation warning in 9 (10)
with view to removal in 10 (11)? Most endorsed libraries I've run across in
the wild do tend to be of the legacy kind and sometimes these projects
don't have their original source code / authors / projects associated.
Several App servers which serve the Java EE space still use the ext
mechanism. Getting them shifted may take some time...

I note in the testing section there was reference to early access builds.
Great and we'll work with Rory et al in QA to get that to the wider
community as soon as possible, but I'm still uncertain whether the time
frames will long enough to get projects to be ready for the change.

> 2. Removed: rt.jar and tools.jar

Stating/Repeating the obvious but the major IDE manufacturers will need to
get enlisted in an early access program to use the rt.jar and tools.jar
replacements. They'll likely? have to build a parallel mechanism as they'll
have to support developers working on Java (dare I say it) 6 through to 9.

I also understand that this is effectively a breaking change for <= Java 7
developers (jrt-fs.jar support for Java 8). That's OK by me, it helps
encourage the world to be on a modern/safe Java and it should be less of an
issue by 2016 anyhow given Java 8's adoption rates.

3. Some of our products certainly do poke and prod at various JDK/JRE/JVM
internals/rarer APIs, as do that of other performance tool vendors. I'm
really not sure how all of these changes will impact us until we get the
early access builds, if we start seeing those in Q1/2 2015 then I'm pretty
confident we'll be able to figure out the new paths required in time. I can
put together a list of players in the market that try to do 'interesting'
things here as well and get them testing early also.


Overall it looks like a major challenge will be to have the community test
their projects, IDEs, App Servers early enough. I can think of a few
surveys & research on Maven Central, BlackDuck etc that could go out to
identify the most important projects to reach out to first. The hardest
part will be getting to the private organisations (The iceberg under the
water that you don't see) that aren't always tied in to the channels which
the typical outreach goes to.

Will do some thinking on this as this mail is now firmly trailing off into
non-jigsaw technical matters :-).

Thanks for the hard work on this, nice to see it coming together, ran
across an annoying logging lib classpath clash today which had me thinking
that "a module system would be really nice around now".


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