Add Automatic-Module-Name clause to jar manifest

[bjorndarri]

Add Automatic-Module-Name clause to jar manifest

[msteiger]

Yes, sounds good. Need to brush up my knowledge about new Java features first a bit. Will review asap.

[msteiger]

Makes sense, thanks for your patience!

[msteiger]

From what I understood now, this should be automatically created when importing the jar in a Java9+ project. Maybe we should instead aim for a explicit module definition through a module-info.java file. What do you think?

[bjorndarri]

I'm all for proper modularization, but the problem is with Java 8 compatibility, which will be broken if you upgrade to Java 9 and add a module-info.java file, although there are ways to mitigate that with multi-release-jar files, but I haven't experimented with that personally.

This way of adding 'Automatic-Module-Name' to the manifest is the simplest way to allow usage in both Java 8 and modularized Java >=9 applications.

I'm using jxmapviewer2 in an application that has both Java 8 and Java 11 versions, so this solution still gets my vote :).

[msteiger]

Okay, sounds reasonable. Thanks. Isn't the Automatic-Module-Name generated by default if you include a jar file without that attribute? Will experiment a bit with it asap and merge your PR then.

[bjorndarri]

Without the manifest attribute a module name is derived from the jar file name, which is basically an unstable fallback mechanism and quite inconvenient to work with.

See for example: Automatic-Module-Name: Calling all Java Library Maintainers
and Explicitly Naming Automatic Java Modules.