Mixin POM fragments

yes, surprisingly there doesn't appear to be an issue for it, though lots of related ones. Adding to that version.

I've been in greater need of this lately - I'll kick a discussion on the development list

Hi,
I've some code to share - tested on Maven 3.0.2 - which composes a Maven POM from different tiles; it's a spike of 2 days work, but I think results are very interesting.

The implementation consists of:

• an implementation of MavenLifecycleParticipant.java (120 lines)
• a components.xml

The attached ZIP file contains a Maven build to produce a JAR that needs to be copied in M2_HOME/lib, a README.txt and a working sample; there are still some issues (e.g. properties inheritance), which are reported in the README, but I think that it gives the idea.

I really hope this could help with this feature implementation.

Just to make sure there is an appropriate discussion on other points-of-view: as a consumer of different maven plugins/other projects there are times when each individual plugin/project requires a large amount of configuration within the pom (particularly third-party plugins). If mixin is intended to help mitigate this problem, great, just didn't want to assume without asking

Examples include the maven-gwt-plugin which requires a good amount of configuration, as well as Enunciate. Having those plugins be able to provide example mixin file that only focuses on their particular plugin will avoid a lot of merging problems that usually occur in sometimes very large pom.xml files.

Maurizio, your maven-tiles seems very promising.

Do you still use it today?
Have you made any improvements to it?
By using it, have you bumped into new problems that you haven't thought of?
How about making it into a github project, or something?

Use "import" scope; that's how you can define a POM for particular types of projects (see issue description) and then add those dependencies to your project. I would say the "import" scope is the Mixin you want.

http://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html

@Tony

• Yes, I still use it sometimes, but being a customisation on the Maven distro (and not a plugin) it is really hard to distribute and build collaboration around it
• No improvements have been made so far
• As above, no changes were made, but probably the biggest issue right now is find a way to implement it as a Maven plugin
• I'm in, will create a github project in the weekend

@Paul, the Mixin feature aims to inherit <build> behaviours, not (only) dependencies. Read more here http://stackoverflow.com/questions/2456375/how-to-use-maven-3-mixins

Dunno.
IMO, import scope was a very important step for maven as it is a move towards the "favor composition over inheritance" design principle for poms.
However that limits using composition for project dependencies.

There's nothing that import scopes can do for me if I want to make a reusable piece of build behaviour, like for example, using the maven-dependency-plugin to unpack a few dependencies during the proccess-resources phase.

Please see

• MNG-5127
• http://stackoverflow.com/questions/11749375/import-maven-plugin-configuration-by-composition-rather-than-inheritance-can-it
• http://stackoverflow.com/questions/10245621/how-to-inherit-from-a-multimodule-maven-project-with-all-its-goodies

Now that maven-tiles has been successfully packed as an open source project,
I made a small project that demonstrates how, using maven-tiles, one can get the desired mixin behaviour.

See attached daddy3.zip

Thanks Maurizio!