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Maven: How to Create a Release

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You are working on your project and now the time has come where you would like to create a release of your project. So how to do this with Maven?

There are existing in general several solutions to achieve the goal. Those different solutions will be described in this article.

Maven Release Plugin

The most obvious one and probbaly most suggested variant is to use the Maven Release Plugin to create a release.

So as a short overview how the Maven Release plugins works is:

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mvn release:prepare ..

So you call the prepare goal of the plugin which will do several checks to be sure you will get a reproducible state of your project. By default you can give the release version of your project interactivaly or if you like to take the defaults you can handle this via --batch-mode option. So after changing the pom file a build will run to make sure everything works well and finally a tag in your version control will be created and the next development version will be set in your pom files.

So next you will call the final part of Maven Release plugin the perform goal which will checkout the code you have tagged in the previous step and run deploy site-deploy on this checked out state. Often you call the above goal in one go which means:

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mvn release:prepare release:perform --batch-mode

All your pom files will automatically updated with the new version etc. So no manual work needed here.

If you think about this scenario you might say: Why do I need to build my project during the release creation cause I already built my project before? The intention for the Maven Release Plugin is to use it from your own computer or where you do not have the support of a CI solution which creates the releases. Furhtermore this can also be based on the usage of GPG keys to sign artifacts etc. which only exist on your own machine so the Maven Release Plugin is a good way to handle releases from your own machine. Maven Release Plugin is also used to release all Maven Plugins of the Apache Maven Project.

Versions Maven Plugin

So an other variant to create a release can be achieved by using the Versions Maven Plugin which you can use to create a release.

What you have to do is more or less the same as Maven Release Plugin would do. You need to check if you missed to checkin sources etc. and afterwards you can change the pom versions of your project by using the following:

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mvn versions:set -DnewVersion=1.0.0

and all pom versions will be changed accordingly. Now you can simply checkin the changed pom files and tag the code state and make:

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mvn clean deploy

which will build your whole project and deploys the generated artifacts into the configured remote repositories. Now you would like to continue developement so you need to change the pom versions via:

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mvn version:set -DnewVersion=1.0.1-SNAPSHOT

And you need to checkin in the changed pom files and now you can continue with your developement for the next release.

You can of course script the above steps or better is to move those steps into a CI solution like Jenkins.

This approach prevents some builds of your project but you need to change the pom versions and do some checkins.

Super Fast Releases

Starting with Maven 3.2.1 you can define the pom version by using the following possible properties: ${revision}, ${sha1} and ${changelist}. The example below will show one usage of this:

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  ..
  <parent>
    <groupId>com.soebes.smpp</groupId>
    <artifactId>smpp</artifactId>
    <version>2.2.1</version>
  </parent>

  <groupId>com.soebes.examples.j2ee</groupId>
  <artifactId>parent</artifactId>
  <version>${revision}</version>
  <packaging>pom</packaging>
  ..

This is a parent of a larger multi module build which contains serveral childs which look like this:

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  <modelVersion>4.0.0</modelVersion>

  <parent>
    <groupId>com.soebes.examples.j2ee</groupId>
    <artifactId>parent</artifactId>
    <version>${revision}</version>
  </parent>

  <artifactId>service</artifactId>
  <dependencies>
    <dependency>
      <groupId>com.soebes.examples.j2ee</groupId>
      <artifactId>service-client</artifactId>
      <version>${project.version}</version>
    </dependency>
    ...

   ..

Based on that you can now build your project simply by using the following:

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mvn -Drevision=1.0.0-SNAPSHOT clean package

or to deploy a SNAPSHOT you can simply do this via:

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mvn -Drevision=1.0.0-SNAPSHOT clean deploy

So there is no need to change the pom files and checkin. But there exists a drawback. You need to define the -Drevision=... for every call of Maven which is not very convenient.

You can handle this by using the following profile:

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  <profiles>
    <profile>
      <id>default-version</id>
      <activation>
        <property>
          <name>!revision</name>
        </property>
      </activation>
      <properties>
        <revision>1-SNAPSHOT</revision>
      </properties>
    </profile>
  </profiles>

which will define the revison in case the property has not been given on command line by using a default value 1-SNAPSHOT.

Starting with Maven 3.3.1 you can configure Maven command line parameters in a .mvn/maven.config file which contains the following for our case:

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-Drevision=1.0.0-SNAPSHOT

So with Maven 3.3.1+ you can now simply call Maven via:

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mvn clean deploy

More convenient? No profile needed.

But wait. What if i like to create a different version? Yes you need to change the .mvn/maven.config file and you should of course checkin the change in your version control.

Unfortunately you can’t overwrite the property which you have defined in the .mvn/maven.config via command line like this:

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mvn clean deploy -Drevision=2.0.0-SNAPSHOT

This problem has already been adressed and solved for the upcoming Maven 3.4.0 release where you can simply do that via the latter.

Starting with Maven 3.4.0 you do not need a profile so you can define a default value for your revision in .mvn/maven.config file and overwrite the value always via command line. This is very convenient in CI tools etc. and furthermore eliminates the usage of those version numbers in your pom file which always produce conflicts if you do a merge from one branch to another.

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