[gentoo-soc] Gentoo Maven Integration - Weekly Report #10

[Kasun Gajasinghe]

Hi all,
-----------------Goal-----------------
The goal of this project is to be easily able to write ebuilds for
upstream projects that use Apache Maven as the build system. The Maven
integration allows to natively use Apache Maven in Java packages in
the main tree. The current system work around the support for Maven
projects by transforming them to Ant. It generates build.xml via “mvn
ant:ant” command and sanitizes that. This conversion too has some
problems and needs to fixed. With this project, developers gains the
ability to use native Maven support for writing ebuilds and will get
full support for using maven-to-ant feature.

-----------------Progress-----------------
Last week has been spent on the java-maven-2 eclass as well as on pom
rewriting. The eclass is responsible for invoking maven for packaging
the maven-based builds, and installing the artifacts. There were few
additions to the eclass, but not very large scale. Written
documentation for the eclass.
In the mean time, I've been looking at the remaining plugins including
maven-surefire-plugin, and fixing the configuration bits. Right now,
all the basic plugins required are up and running for simple projects.
There is several compatibility issues I've been facing these days when
it comes to maven's approach of building vs Gentoo build system. So,
some parts of the week has been spent on getting know the internals of
maven better. I've discussed with the maven community in mailing list
as well as irc for some insights. Some outcomes though sounded sweet,
but turned out misleading later on.

Two major issues I had was these. First, the issue with specifying the
maven plugin versions. Maven plugins are installed separately of maven
package. mvn needs the plugin versions to operate correctly. The
versions need to match the installed plugins in Gentoo. Discussion at
[1] was regarding this at Maven dev list. That was apart from the
discussions I had with mentor. Two suggested solutions (settings.xml
and plugin-registry.xml thing) turned out impossible after spending
valuable time on them. The remaining solution is not an ideal
solution, but we got to settle for it. Basically, the current idea is
to have a Gentoo maven super pom, that will override the
maven-super-pom and have the set of installed plugin versions
specified. This will continue in this week.

Second issue, was maven's enormous number of parent poms with
packaging 'pom'. Most of these are identical to each other, and
doesn't need to be/ can't be installed. So, we needed to have a
mechanism to have more control over the parent pom of a given project.
This has been implemented currently. Changed the pom rewriter as well
the eclass to conform to this. The controlling happens via
"MAVEN_PARENTPOM_UNIQUE_ID" and "MAVEN_REWRITE_PARENT_OF_SUBMODULES"
(=Y/N) variables. The format is -
MAVEN_PARENTPOM_UNIQUE_ID="parentGroupId:parentArtifactId:parentVersion"
or just "parentVersion".  MAVEN_REWRITE_PARENT_OF_SUBMODULES tells
whether to rewrite the parent-element of sub-modules as well.
maven-plugins-by-ant-2.2.1 is a sample ebuild for this [3].

[1] http://maven.40175.n5.nabble.com/Set-specific-plugin-versions-for-a-project-issue-in-plugin-registry-xml-maven-metada-local-xml-td4629803.html
[2] http://maven.40175.n5.nabble.com/surefire-api-not-relocating-the-classes-of-commons-lang-though-it-s-in-m-shade-p-config-td4658872.html#none
[3] http://overlays.gentoo.org/proj/java/browser/gsoc-maven-overlay/dev-java/maven-plugins-by-ant/maven-plugins-by-ant-2.2.1.ebuild?rev=8679

Thanks,
--Kasun

--
~~~*******'''''''''''''*******~~~
Kasun Gajasinghe,
University of Moratuwa,
Sri Lanka.
Blog: http://blog.kasunbg.org
Twitter: http://twitter.com/kasunbg