The goal of this tutorial is to configure our project so that executing the following commands on the CI server:

  • mvn release-candidate:updateVersion - sets the pom.xml project version according to the format we specify
  • mvn clean package - produces an artifact of our project and outputs its version in a format the CI server understands

Target version format

For the purpose of this tutorial let’s assume that we’re working on version 1.0.0 of an awesome-app project, and we’d like the target version format to include:

  • the API version - 1.0.0
  • a build timestamp - 20150801
  • and a git hash - 1b4d455

which means that the version format looks like this:

{{ api_version }}-{{ timestamp('YYYYMMdd') }}.${revision}

and an example version would be:

1.0.0-20150801.1b4d455

Note: Maven compares the qualifiers of two versions with an identical api version part using string comparison and for this reason when using both a timestamp and a git hash in the qualifier it makes sense to have the timestamp occur first.

POM configuration

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <groupId>com.example</groupId>
    <artifactId>awesome-app</artifactId>

    <version>1.0.0-SNAPSHOT</version> <!-- (1) -->

    <properties>
      <revision>0000000</revision>    <!-- (2) -->

        [...]
    </properties>

    <build>
      <plugins>                       <!-- (3) -->
        <plugin>
          <groupId>com.smartcodeltd</groupId>
          <artifactId>release-candidate-maven-plugin</artifactId>
          <version>1.0-201609171818.3e8187b</version>
          <executions>                <!-- (4) -->
            [ todo: configure the plugin ]
          </executions>
        </plugin>
      </plugins>
    </build>

    [...]
</project>

As you can see, we’ve done several things in the pom:

  1. the project version is set to 1.0.0-SNAPSHOT
  2. the ${revision} parameter we’ll use in the final version number has a default value of 0000000 (this value will be replaced by an actual git hash injected during the build process)
  3. release-candidate-maven-plugin is added to build/plugins and ready to be configured (4)

Note: You can find more on configuring Maven build plugins in the official documentation.

Release Candidate configuration

Due to a limitation in Maven, release-candidate goals need to be run in two stages:

  • first, to update the pom.xml file
  • second, to build the project artifact and let the CI server know the new version number

Because of that, two <execution /> sections need to be present.

First execution

In order to configure the first execution, add the following section under <executions>:

<execution>
  <id>default-cli</id>
  <goals>
    <goal>updateVersion</goal>
  </goals>
  <configuration>
    <releaseVersionFormat>{{ api_version }}-{{ timestamp('YYYYMMddHHmm') }}.${revision}</releaseVersionFormat>
  </configuration>
</execution>

Note: Setting the execution id to default-cli and the goal to updateVersion means that the configuration will be applied when mvn release-candidate:updateVersion command is executed on the CI server. (Learn more).

To learn more about the {{ tokens }} used to configure the releaseVersionFormat, consult the documentation of the updateVersion goal.

Second execution

To configure the second execution, add the below section:

<execution>
  <goals>
    <goal>version</goal>
  </goals>
  <configuration>
    <outputTemplate>PROJECT_VERSION={{ version }}</outputTemplate>
  </configuration>
</execution>

Specifying the outputTemplate as above makes the plugin produce the following output:

[INFO] Scanning for projects...
[...]
[INFO] --- release-candidate-maven-plugin:1.0-201609171818.3e8187b:version (default) @ release-candidate-maven-plugin ---
[INFO] Detected version: '1.0.0-SNAPSHOT'
PROJECT_VERSION=1.0.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[...]

A deterministic output format makes it easy for the CI server to parse the output and set the build description for example.

The version goal is tied to the package phase of the Maven build lifecycle by default, which means that whenever you call mvn package, the version goal will get invoked as well.

Note that the outputTemplate parameter can be a multi-line string, and that it also understands {{ tokens }}.

Summary

So far our plugin configuration looks like this:

<plugin>
    <groupId>com.smartcodeltd</groupId>
    <artifactId>release-candidate-maven-plugin</artifactId>
    <version>1.0-201609171818.3e8187b</version>
    <executions>
      <execution>
        <id>default-cli</id>
        <goals>
          <goal>updateVersion</goal>
        </goals>
        <configuration>
          <releaseVersionFormat>{{ api_version }}-{{ timestamp('YYYYMMddHHmm') }}.${revision}</releaseVersionFormat>
        </configuration>
      </execution>
      <execution>
        <goals>
          <goal>version</goal>
        </goals>
        <configuration>
          <outputTemplate>PROJECT_VERSION={{ version }}</outputTemplate>
        </configuration>
      </execution>
    </executions>
</plugin>

and allows the following commands to be executed on the CI server:

mvn release-candidate:updateVersion -Drevision=`git rev-parse --short HEAD`

which updates the pom.xml project version, and

mvn clean package

which now also produces output the CI server can parse in order to set the build description.

Optional: Enforcer configuration

As you’ve noticed, the revision parameter is injected by the CI server when the updateVersion goal is called.

If you want to make sure that the parameters passed to Maven are valid - use the Maven Enforcer Plugin.

In the case of our example project where the injected parameter is a git hash, an appropriate enforcer rule might looks as follows:

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-enforcer-plugin</artifactId>
  <version>1.4</version>
  <executions>
    <execution>
      <id>default-cli</id>
      <goals>
        <goal>enforce</goal>
      </goals>
      <configuration>
        <rules>
          <requireProperty>
            <property>revision</property>
            <message>Please specify the `revision` property</message>
            <regex>[a-f0-9]{7}</regex>
            <regexMessage>revision should be a 7 character long identifier, generated by running `git rev-parse --short HEAD`</regexMessage>
          </requireProperty>
        </rules>
        <fail>true</fail>
      </configuration>
    </execution>
  </executions>
</plugin>

To make sure that the enforcer rule is called, add the validate goal when invoking updateVersion:

mvn validate release-candidate:updateVersion -Drevision=`git rev-parse --short HEAD`

Next: find out more about the updateVersion and version goals.


Your feedback matters!

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Found a bug? ⇒ Raise an issue or submit a pull request

Have feedback, interested in the project news? ⇒ Get in touch and follow me on twitter: @JanMolak

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Version: 1.0-201609171818.3e8187b. Last Published: 2016-09-17.