docker-maven-plugin

A Maven plugin for building and pushing Docker images.

Why?

You can use this plugin to create a Docker image with artifacts built from your Maven project. For example, the build process for a Java service can output a Docker image that runs the service.

Setup

You can specify the base image, entry point, cmd, maintainer and files you want to add to your image directly in the pom, without needing a separate Dockerfile. If you need other commands such as RUN or VOLUME, then you will need to create a Dockerfile and use the dockerDirectory element.

Specify build info in the POM

This example creates a new image named example, copies the project's jar file into the image, and sets an entrypoint which runs the jar. Change VERSION GOES HERE to the latest tagged version.

<build>
  <plugins>
    ...
    <plugin>
      <groupId>com.spotify</groupId>
      <artifactId>docker-maven-plugin</artifactId>
      <version>VERSION GOES HERE</version>
      <configuration>
        <imageName>example</imageName>
        <baseImage>java</baseImage>
        <entryPoint>["java", "-jar", "/${project.build.finalName}.jar"]</entryPoint>
        <!-- copy the service's jar file from target into the root directory of the image --> 
        <resources>
           <resource>
             <targetPath>/</targetPath>
             <directory>${project.build.directory}</directory>
             <include>${project.build.finalName}.jar</include>
           </resource>
        </resources>
      </configuration>
    </plugin>
    ...
  </plugins>
</build>

Use a Dockerfile

To use a Dockerfile, you must specify the dockerDirectory element. If specified, the baseImage, maintainer, cmd and entryPoint elements will be ignored. The contents of the dockerDirectory will be copied into ${project.build.directory}/docker. Use the resources element to copy additional files, such as the service's jar file.

<build>
  <plugins>
    ...
    <plugin>
      <groupId>com.spotify</groupId>
      <artifactId>docker-maven-plugin</artifactId>
      <version>VERSION GOES HERE</version>
      <configuration>
        <imageName>example</imageName>
        <dockerDirectory>docker</dockerDirectory>
        <resources>
           <resource>
             <targetPath>/</targetPath>
             <directory>${project.build.directory}</directory>
             <include>${project.build.finalName}.jar</include>
           </resource>
        </resources>
      </configuration>
    </plugin>
    ...
  </plugins>
</build>

Usage

You can build an image with the above configurations by running this command.

mvn clean package docker:build

To push the image you just built to the registry, specify the pushImage flag.

mvn clean package docker:build -DpushImage

By default the plugin will try to connect to docker on localhost:2375. Set the DOCKER_HOST environment variable to connect elsewhere.

DOCKER_HOST=tcp://<host>:2375

You can also bind the build goal to the package phase, so the container will be built when you run just mvn package. If you have a multi-module project where a sub-module builds an image, you will need to do this binding so the image gets built when maven is run from the parent project.

<plugin>
  <groupId>com.spotify</groupId>
  <artifactId>docker-maven-plugin</artifactId>
  <version>VERSION GOES HERE</version>
  <executions>
    <execution>
      <phase>package</phase>
      <goals>
        <goal>build</goal>
      </goals>
    </execution>
  </executions>
</plugin>

To remove the image named foobar run the following command:

mvn docker:removeImage -DimageName=foobar

For a complete list of configuration options run: mvn com.spotify:docker-maven-plugin:<version>:help -Ddetail=true

Authenticating with Private Registries

To push to a private Docker image registry that requires authentication, you can put your credentials in your Maven's global settings.xml file as part of the <servers></servers> block.

<servers>
  <server>
    <id>docker-hub</id>
    <username>foo</username>
    <password>secret-password</password>
  </server>
</servers>

Now use the server id in your project pom.xml.

<plugin>
  <plugin>
    <groupId>com.spotify</groupId>
    <artifactId>docker-maven-plugin</artifactId>
    <version>VERSION GOES HERE</version>
    <configuration>
      [...]
      <serverId>docker-hub</serverId>
      <registryUrl>https://index.docker.io/v1/</registryUrl>
    </configuration>
  </plugin>
</plugins>

<registryUrl></registryUrl> is optional and defaults to https://index.docker.io/v1/ in the Spotify docker-client dependency.

Releasing

Commits to the master branch will trigger our continuous integration agent to build the jar and release by uploading to Sonatype. If you are a project maintainer with the necessary credentials, you can also build and release locally by running the below.

mvn release:clean
mvn release:prepare
mvn release:perform