Re: MJAR maven 4 usage and deps

let say I have a class AwesomeService, i want a java 8 impl (src/main/java)
which uses jackson 2 and a java 25 version which uses jackson 3
(META-INF/versions/25).
how do I handle that since both are literally like different codebase.
in other words it seems we only handle java specificities but in today's
world the java version related specificities is about transitive
dependencies too so we should be able to configure a <dependencies> block
per source directory IMHO with overrides of the default block.

The current maven 3 workaround to have a multimodule project works well but
if we want it to be a first citizen in maven 4 it seems we just missed the
core design of the feature if it is not possible.

Adding dependencies block in source dirs can be a no brainer but overrides
are harder since GA can be different - I even potentially have a case where
the lib is not the same at all, like serp (java 6+) vs asm (java 8+) vs
classfile API (java 25+, no dep).

(if unclear I'd like we limit the modelVersion we do promote with promoting
maven 4, I know we can change often but it is hurtful everytime we do so
trying to mitigate it ensuring we cover the common use cases)

Romain Manni-Bucau
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Le jeu. 27 août 2026 à 09:37, Martin Desruisseaux via dev <
[email protected]> a écrit :

> Le 27/08/2026 à 09:19, Romain Manni-Bucau a écrit :
>
> > I'm having a headache to see how our new design with types for
> dependencies
> > and mjar layout work together: how can i get different deps for different
> > java version in the same jar?
>
> I'm not sure which dependencies the question is about:
>
>   * The "Classpath" attribute in MANIFEST.MF?
>   * The module-info.class?
>   * The pom.xml in META-INF/maven directory?
>
> To my knowledge, there is no mechanism for providing different values of
> the above depending on the version. It could be possible for
> `module-info.class` but I'm not completely sure that it would work.
>
>      Martin
>
>