Year: 2010

A pattern for WebStart in Maven

Java WebStart and JNLP can be finicky beasts, especially when paired with Maven-generated websites and artifact repositories. Over the last few months I’ve developed POM and JNLP template patterns that I think are useful when used with the webstart-maven-plugin:jnlp goal; the main advantage is that applications can be WebStarted directly from the repository, which means that the version available is always the latest -SNAPSHOT or release.

In the POM I define two variables, site.baseUrl and artifactUrl. site.baseUrl defines the server and root path where all Maven-generated websites are published; it has a prefix because usually I’d only set it once in the corporate POM. artifactUrl is the full URL of the project-specific website.

By default both site.baseUrl and artifactUrl point to the location where -SNAPSHOT sites are published, usually by a CI system. They’re overridden in two profiles: release switches site.baseUrl to the release website (which is applied to artifactUrl, so there’s no need to set it again), and devel sets artifactUrl to the local target directory (and omits site.baseUrl, which ends up unused).

<project>
...
  <properties>
    <site.baseUrl>http://repository/snapshot-site/</site.baseUrl>
    <artifactUrl>${site.baseUrl}/${project.artifactId}</artifactUrl>
  </properties>
...
  <profiles>
    <profile>
      <id>release</id>
      <properties>
        <site.baseUrl>http://repository/release-site/</site.baseUrl>
      </properties>
      <distributionManagement>
        <site>
          <id>release-site</id>
          <url>dav:${artifactUrl}</url>
        </site>
      </distributionManagement>
    </profile>
    <profile>
      <id>devel</id>
      <properties>
        <artifactUrl>file://${project.build.directory}</artifactUrl>
      </properties>
    </profile>
  </profiles>
...
</project>

In the JNLP template, the codebase is set to artifactUrl, which means that the resulting JNLP will retrieve any artifact dependencies from the snapshot, release or local output directories.

<jnlp
  spec="$jnlpspec"
  codebase="${artifactUrl}/jnlp/"
  version="$project.Version"
>
...
</jnlp>

Note that the artifact dependencies still need to be copied into the jnlp directory, which webstart-maven-plugin:jnlp does by default. It would be nice to be able to get them from their canonical locations on the repository, but that’s not easily accomplished.