Hello all
This is a proposal for a major restructuring of Apache SIS source code.
This proposal would impact SIS developers, but not users. For all users,
package names and Maven coordinates will stay unchanged.
The goal is to apply Java Platform Module System (JPMS) modularisation,
also known as "Jigsaw", on the Apache SIS project. At the minimum, JPMS
requires that we add a "module-info.java" file at the root of every
modules. It has various consequences, some of them already resolved
(e.g. ensuring that no module use the same package name, adapting
various usages of ServiceLoader, resources and reflections for module
encapsulation). However while some JPMS is possible with Maven, taking
full advantage of JPMS requires source code restructuring. This is
because all Java versions up to Java 8 supported only one way to
organize the source code, known as Package Hierarchy, but Java 9
introduced a second way to organized source code, known as Module
Hierarchy. Not many peoples are aware of this second layout, maybe
because it is not supported by Maven or Gradle. But it is the layout
used by OpenJDK for example.
Getting Maven to work with Module Hierarchy would be very difficult.
However it is possible with Gradle, because of its flexibility. So the
proposal to restructure source code according the Module Hierarchy
implies migrating from Maven to Gradle. This work has been done and
tested on a branch, and has reached a point where I think it can be
submitted to SIS PMC. The following link describes in more details what
is a Module Source Hierarchy, how we propose to restructure SIS source
code, and how to get Gradle to work with it.
https://geomatys.github.io/draft/Modularization.html
Content:
* Overview of directory layout change
* Apache SIS restructuring
* Gradle configuration for Module Source Hierarchy
o Gradle issues and workarounds
* Advantages of Source Module Hierarchy
* Limitations of Source Module Hierarchy
* Quasi-blocker Maven bug
* Conclusion
o Ideas for Gradle evolution
I would like to start a discussion about whether peoples agree/disagree
with the proposed plan. If we reach an agreement, I will prepare later
in August a pull request to be submitted to PMC vote. In the meantime, I
plan to fill issues on Gradle GitHub for making proposals for easier
support of Module Hierarchy in Gradle.
Reminder: this change should have no significant impact on users. The
same Apache SIS JAR files will continue to be deployed on Maven Central
under the same groupId and artifactId, with the same "org.apache.sis"
packages.
Martin
