Could use a module name

[ghost314]

I decided to try building my latest project with the java module system so I can better understand how it works. I found myself needing to generate a package URL so I dropped in a reference to this project and a warning popped up.

Since no module name is declared in the jar manifest, it seems the module system defaults to using the jar file name as the module name. Apparently this can cause a major problem if the name changes (either because a proper name was picked, or because the name of the jar file changed) and 2 different modules try to reference it with different names. Maven even goes as far as to beg me not to publish my project until the issue is fixed.

Personally I wonder if it's really that big a deal when I could presumably just release a new version of my project referencing the new module name, but anyhow it's an easy fix. You basically just need to pick a module name and add it to the manifest, which can be done while still compiling and running on JDK 8. For instance here is the jar manifest for the apache commons codec project.

This post has a lot more info on the matter.

[ppkarwasz]

Some Maven plugins like Moditect or BND allow the generation of a proper module-info.class descriptor during the build (even on JDK 8).
I am a big fan of the latter, since it is a fully-fledged solution that:

• Generates an OSGi bundle descriptor.
• Generates a JPMS module doescriptor.
• It detects subtle relationships with dependencies, e.g. when a requires transitive is required.
• The bnd-baseline-maven-plugin detects and categorizes changes into MICRO, MINOR and MAJOR.

[jeremylong]

I'm all for using BND.

[ppkarwasz]

I can make a PR then.

[dwalluck]

Some Maven plugins like Moditect or BND allow the generation of a proper module-info.class descriptor during the build (even on JDK 8).

I somehow thought that a proper module would make it incompatible with Java 8. If your pull request supersedes #96, feel free to add "Closes #96" to yours, in which case it would close this one automatically when merged.

[ppkarwasz]

I somehow thought that a proper module would make it incompatible with Java 8.

Java 8 does not know anything about module-info.class, so it doesn't look for this file. Only Java 9+ will try to retrieve it.