Project Jigsaw: Phase Two

David Bosschaert david.bosschaert at
Wed Jul 2 19:22:45 UTC 2014

Thanks for posting this Mark.

One thing that I think should also be a requirement is that the module
metadata should be in an easily extensible format so that tools and
other module systems such as OSGi can augment it with additional

In OpenJDK project Penrose [1] we prototyped a solution based on the
previous incarnation of Jigsaw that used JSON for this, but another
option could be XML or something similar. I think that storing the
module metadata in the .class file is certainly not a good option
here, as it's very hard to extend by other tools.

Best regards,



On 2 July 2014 17:47,  <mark.reinhold at> wrote:
> Project Jigsaw has, for the last several years, been in an exploratory
> phase in which we've designed and prototyped one particular approach [1]
> to addressing a draft set of requirements [2].
> It's now time to switch gears and focus on creating a production-quality
> design and implementation suitable for JDK 9 and thence Java SE 9, as
> previously proposed [3].
> To begin this phase I've drafted a new document to collect goals and
> requirements [4].  It reflects a new emphasis on security, as motivated
> by recent experience [5], it takes into account lessons learned from the
> prototype, and it's written at a broader and more abstract level than the
> previous document [2] so as not to over-constrain the solution space.
> This document will be one of the starting points of the upcoming Java
> Platform Module System JSR.
> Please send comments and suggestions on the new goals and requirements
> document [4] to this list, jigsaw-dev at
> Jigsaw as a whole will bring enormous changes to the JDK; it would be
> unwise to wait until it's completely finished before merging any of it.
> Our intent, therefore, is to proceed in large steps, each of which will
> have a corresponding JEP.  The first three JEPs, which I'll also post
> here for review, will propose a specific modular structure for the JDK,
> reorganize the JDK source code (but not binaries) along those lines,
> and then later modularize the binary images.
> A fourth JEP will introduce the module system itself, which will be
> aligned with the module-system JSR.  It may seem odd that the module
> system JEP comes last, but the earlier JEPs need make only minimal
> assumptions about its capabilities, hence work on them can proceed
> in parallel with work on the module-system JEP and JSR.
> - Mark
> [1]
> [2]
> [3]
> [4]
> [5]

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