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Plexus parent POM

Every project in the Codehaus Plexus organization inherits this parent POM. It sets plugin versions, the Java and Maven baselines, code formatting, reporting, and the release setup, so each project carries almost no build configuration of its own.

To inherit it, add the following to your project's POM:

<parent>
  <groupId>org.codehaus.plexus</groupId>
  <artifactId>plexus</artifactId>
  <version>VERSION</version>
</parent>

Replace VERSION with a released version. The badge on the project page links to them.

What you get

Baselines

The following table lists the settings the parent POM fixes:

Setting Value
Java, through the javaVersion property 8, which sets maven.compiler.source, target, and release
Minimum Maven to build 3.9.0, raised from 3.6.3 in version 27
Source encoding UTF-8
Annotation processing Off, through maven.compiler.proc=none

To raise the Java baseline, override the javaVersion property in your own POM. The plexus-sec-dispatcher and plexus-xml 4.x projects set it to 17.

To use annotation processing, turn it on deliberately in your own POM.

Enforced at build time

The maven-enforcer-plugin plugin fails the build on a Maven version below the minimum and on a JDK below the baseline. Through extra-enforcer-rules, it also fails on any dependency containing bytecode newer than your compiler target.

That last rule surprises people. A dependency compiled for a later JDK than you target fails the build rather than the application.

Formatting

Spotless runs at the process-sources phase and formats three kinds of file:

  • Java, with palantir-java-format. Spotless removes unused imports and orders the rest as javax, java, everything else, then static imports.
  • POM files, sorted with sortPom.
  • Markdown, with flexmark.

What Spotless does with a violation depends on where the build runs. On your own machine, where the CI environment variable isn't set, the format profile sets spotless.action=apply and the build rewrites your sources. In CI, where CI is set, the format-check profile sets the action to check and the build fails instead. When CI fails on formatting, run mvn spotless:apply and commit the result.

Note: Spotless formats every **/*.md file. Parent 26 and later exclude **/src/site/markdown/**, because flexmark rewrites the fence that closes a YAML front matter block, which drops the page's title and author without reporting an error. Parent 25 has no such exclusion. If you use parent 25 and keep site sources in Markdown, add the exclusion to your own POM.

Reproducible builds

The project.build.outputTimestamp property is set, and Reproducible Central verifies every project here. Keep the property set, and change its value only as part of a release.

Reporting

Project information reports run by default. The reporting profile adds Javadoc, JXR, surefire, PMD/CPD, and taglist. To build a site with all of them:

mvn -Preporting site

A site built without the reporting profile contains no API documentation, so pass the profile whenever you publish.

Publishing

Snapshots and releases go to the Sonatype Central Portal. Your project inherits distributionManagement, but each project overrides the site element to point at its own gh-pages branch:

<distributionManagement>
  <site>
    <id>github:gh-pages</id>
    <url>${project.scm.developerConnection}</url>
  </site>
</distributionManagement>

The maven-site-plugin plugin runs with skipDeploy, so the maven-scm-publish-plugin plugin publishes sites rather than the site:deploy goal.

Releasing

For the full procedure, including site publishing, see RELEASING.md. The short version:

mvn release:prepare
mvn release:perform

The maven-release-plugin plugin is configured with <goals>deploy</goals> and <releaseProfiles>plexus-release</releaseProfiles>, so release:perform activates the plexus-release profile. That profile turns on GPG signing, attaches sources and a source-release assembly, and enables Njord, which is registered as a build extension.

Njord is configured with autoPublish=true and publishingType=automatic, so it publishes the deployment to Maven Central without a manual step in the Portal UI. Outside the release profile, njord.enabled is false, so ordinary builds are unaffected.

Set up a release manager

Add a Central Portal token to your personal settings.xml file:

<settings xmlns="http://maven.apache.org/SETTINGS/1.2.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.2.0 https://maven.apache.org/xsd/settings-1.2.0.xsd">
  <servers>
    <server>
      <id>sonatype-central-portal</id>
      <username>TOKEN_USERNAME</username>
      <password>TOKEN_PASSWORD</password>
    </server>
  </servers>
</settings>

Replace the following:

  • TOKEN_USERNAME: the username half of a Central Portal token pair
  • TOKEN_PASSWORD: the password half of the same pair

Generate the pair from your Central Portal account. A token pair isn't your account password.

You also need a published GPG key, because releases are signed.

Reference