Versioning in the java platform module system - proof of concept

[Tom De Wolf]

I am working out a proof of concept to use the module version property and
the version of a ‘requires’    in a useful manner. Details and a link to
github can be found on:

https://devcreativity.wordpress.com/2017/12/29/semantic-versions-in-java-9-modules-as-a-safety-net/

However, I stumbled on behaviour I don’t completely understand:
- printing out the module.getDescription().version() showed a non-empty
value for the jdk modules, explicit modules which got the version through
‘jar --module-version’, and automatic modules like spring.core
- as I understand the Requires.compiledVersion() gets a value when the
dependency module has a version in module.getDescription().version()

The latter is seen when requiring explicit modules, however requiring an
automatic module does not fill in the compiledVersion? Why is that, even
when the module.getDescription().version() shows a value (e.g. spring.core)?

What is used for an automatic module such as spring.core to show
5.0.0.RELEASE as version?

Thanks in advance for any helpful and insightful reply! Any thoughts,
suggestions, remarks on my proof of concept itself are also more than
welcome.

Tom De Wolf