More tips on using the maven2 release plugin

This blog's most frequently visited post was the one I did over a year ago titled "How to create a release using the maven2 release plugin". Automating this portion of our frequent release process without a doubt has saved my team hundreds of hours over the past year. For that reason I would like to provide some new tips I discovered yesterday when I needed to change the subversion comment used by the release plugin when committing any changes.

For teams not using the maven-release-plugin yet, this handy plugin helps automate the complete process when releasing your software. It helps save time by doing the following and more:

• First it will build your project running any tests you specify
• If successful, it will then commit your project into a tag
• Update the tag pom versions from say 1.0.0-SNAPSHOT to 1.0.0
• Change the tag pom SCM URL to correctly point to the tag instead of HEAD
• Most importantly, it will build the release (1.0.0) and upload the artifacts to your companies maven2 repository (archiva now in our case; was artifactory).
• Finally, it will increment the pom versions in HEAD to be the next release (1.0.1-SNAPSHOT).
  

Tip #1 - Change Commmit Comment
By default the maven-release-plugin uses a comment like, [maven-release-plugin] prepare release project-1.0.0, when doing any type of commit such as creating a tag/branch or incrementing the pom versions. Which works wonderful until your team implements a Subversion pre-commit hook requiring all commits to start with certain keywords (Story: ZZZ, Jira: ZZ-N). Luckily the maven-release-plugin has an option to override the comment.

There are two simple ways to provide the plugin with the comment. The first sets the system property, scmCommentPrefix, to the predefined prefix. The second, provides the prefix comment in the pom.

mvn release:clean release:prepare -DscmCommentPrefix=Jira: AC-100 [maven-release-plugin]

<plugins>
 <plugin>
     <groupId>org.apache.maven.plugins</groupId>
     <artifactId>maven-release-plugin</artifactId>
     <configuration>
         <scmCommentPrefix>Jira: AC-100 [maven-release-plugin]</scmCommentPrefix>
     </configuration>
 </plugin>
<plugins>

Tip #2 - Configuration Options via -D
Disappointed that I didn't catch this earlier, especially since I have been using -DpreparationGoals for awhile now, but all of the optional parameters for the prepare goal can be defined with -D rather than in the POM (as above). So if you wanted to change the default tagBase to use /branches instead of the default /tags do the following. However, I would still put this static value in the pom.

mvn release:clean release:prepare -DtagBase=http://project.svn.org/svn/project/branches

Tip #3 - Allow SNAPSHOT dependencies
This new feature is going to be huge for legacy projects who weren't raised with the release plugin. As mentioned in my previous post, previous versions of the release plugin didn't allow you to have SNAPSHOT dependencies; rightfully so too since that wouldn't be a very good practice to have a release depend on a changing dependency. However, I think this feature prevented many projects from using the release plugin because their snapshot depenencies were too many to change and it was just easier to continue doing same old.

Even though I have not used this feature, it would seem now one could release a project using this plugin and still have SNAPSHOT dependencies. However, after creating the release it would still be a good idea to go back in the release and change any SNAPSHOT dependencies to releases.

I believe this is a new feature so you might also want to upgrade to the latest version.