Maven : Multimodule projects and versioning

Question

What are the best practices for software versioning and multimodules projects with Maven?

I mean, when I create a multimodules project with Maven, what is the best approach for the versioning? To use a single version for all the modules (defined in the top project)? To use a version for each module (defined in the POM of each module)? Is there another approach that I'm missing? What are the pros and cons of each approach?

In general, are the different modules released together (possibly sharing the same version number)?

Thanks

Answer 1

Honestly it depends on what you would like to do. Multimodule projects are created for multiple reasons, one of them being you only need to deploy what has changed instead of all modules.

Think about it this way: if you had a non-multi-module project and you only had to change one line in the services layer, you have to rebuild the entire project and deploy all of the code again...even though only your services layer will change.

With multi-module projects, you can regenerate your project and deploy only what changed...your services. This reduces risk and you're assured that only your services module changed.

You also have a multitude of benefits to using multi-module projects that I'm not listing here but there is certainly a huge benefit to NOT keeping your version numbers of your modules in sync.

When you build your project, consider deploying it to a repository that will hold all compatible jars together for builds (each build creates a new folder with the parent-most pom version number). That way, you don't need to keep documentation about which jars are compatible...they're all just deployed together with a build number.