Jigsaw Hackday in London - Anything in particular you want us to look at?

Alan Bateman Alan.Bateman at oracle.com
Tue Jun 23 11:10:04 UTC 2015

On 23/06/2015 10:34, Martijn Verburg wrote:
> Hi all,
> As part of the Adoption Group we're planning on holding a Hackday in London
> for the July/Aug timeframe, primarily as an education/awareness piece
> around Jigsaw (there's lots to catch up on).
> Is there anything in particular you'd like a group of 'users'/developers to
> look at?  I assume basing this off the latest jdk9 forest will be more
> stable than the jigsaw forest.
I would expect/hope that JSR 376 will be further along by then so there 
may be more to talk about and play with at this event.

In the mean-time there is a lot to discuss and prepare. We've been 
warning (and javac has emitted warnings) for many years that 
JDK-internal APIs will not be accessible out of the box so anything that 
reduces or eliminates dependences on internal APIs in popular libraries 
will be a big help. It might be fun to use jdeps on the say the 20 most 
popular libraries to get a feel for the problem.

We've had the initial changes for JEP 220 in JDK 9 for about 6 months. 
This is the JEP that changes the structure of the run-time images. This 
has implications for tools (mostly) that have been used to directly 
accessing rt.jar and other internal files in the legacy images. JEP 220 
comes with a supported interface for accessing classes and resources in 
the run-time image so that may be worth spending time on. There is a 
refresh of this in flight and it should be in by the time you have this 
event. It might be fun to try out the top 20 tools and plugins to see if 
they run with JDK 9 and maybe even hack on one or two of them to use the 
FileSystem API.

Another idea is to look at the module graph in JEP 200, or better still, 
the most up to date graph of modules in the JDK 9 forests. One idea is 
to hack on make/Images.gmk in the top-level repository to force the JDK 
build to produce run-time with a subset of the modules. The primitive 
image building tool that this make file runs will be replaced by a 
linker tool in time but there is enough to hack on to get a feel for the 
modules and what might run (or not run) with a small set of modules. The 
module graph is essentially an API so any feedback or usage of that API 
would be useful too.


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