Java EE, Docker and Maven (Tech Tip #89)

Arun GuptaMay 22nd, 2015Last Updated: May 22nd, 2015

0 28 2 minutes read

Java EE applications are typically built and packaged using Maven. For example, github.com/javaee-samples/javaee7-docker-maven is a trivial Java EE 7 application and shows the Java EE 7 dependency:

<dependencies>
    <dependency>
        <groupId>javax</groupId>
        <artifactId>javaee-api</artifactId>
        <version>7.0</version>
        <scope>provided</scope>
    </dependency>
</dependencies>

And the two Maven plugins that compiles the source and builds the WAR file:

<plugin>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.1</version>
    <configuration>
        <source>1.7</source>
        <target>1.7</target>
    </configuration>
</plugin>
<plugin>
    <artifactId>maven-war-plugin</artifactId>
    <version>2.3</version>
    <configuration>
        <failOnMissingWebXml>false</failOnMissingWebXml>
    </configuration>
</plugin>

This application can then be deployed to a Java EE 7 container, such as WildFly, using the wildfly-maven-plugin:

<plugin>
    <groupId>org.wildfly.plugins</groupId>
    <artifactId>wildfly-maven-plugin</artifactId>
    <version>1.0.2.Final</version>
</plugin>

Tests can be invoked using Arquillian, again using Maven. So if you were to package this application as a Docker image and run it inside a Docker container, there should be a mechanism to seamlessly integrate in the Maven workflow.

Docker Maven Plugin

Meet docker-maven-plugin!

This plugin allows you to manage Docker images and containers from your pom.xml. It comes with predefined goals:

Goal	Description
`docker:start`	Create and start containers
`docker:stop`	Stop and destroy containers
`docker:build`	Build images
`docker:push`	Push images to a registry
`docker:remove`	Remove images from local docker host
`docker:logs`	Show container logs

Introduction provides a high level introduction to the plugin including building images, running containers and configuration.

Run Java EE 7 Application as Docker Container using Maven

TLDR;

Create and Configure a Docker Machine as explained in Docker Machine to Setup Docker Host
Clone the workspace as: git clone https://github.com/javaee-samples/javaee7-docker-maven.git
Build the Docker image as: mvn package -Pdocker
Run the Docker container as: mvn install -Pdocker
Find out IP address of the Docker Machine as: docker-machine ip mydocker

Access your application

javaee7-docker-maven> curl http://192.168.99.100:8080/javaee7-docker-maven/resources/persons
<?xml version="1.0" encoding="UTF-8" standalone="yes"?><collection><person><name>Penny</name></person><person><name>Leonard</name></person><person><name>Sheldon</name></person><person><name>Amy</name></person><person><name>Howard</name></person><person><name>Bernadette</name></person><person><name>Raj</name></person><person><name>Priya</name></person></collection>

Docker Maven Plugin Configuration

Lets look little deeper in our sample application.

pom.xml is updated to include docker-maven-plugin as:

<plugin>
    <groupId>org.jolokia</groupId>
    <artifactId>docker-maven-plugin</artifactId>
    <version>0.11.5-M1</version>
    <configuration>
        <images>
            <image>
                <alias>user</alias>
                <name>arungupta/javaee7-docker-maven</name>
                <build>
                    <from>arungupta/wildfly:8.2</from>
                    <assembly>
                        <descriptor>assembly.xml</descriptor>
                        <basedir>/</basedir>
                    </assembly>
                    <ports>
                        <port>8080</port>
                    </ports>
                </build>
                <run>
                    <ports>
                        <port>8080:8080</port>
                    </ports>
                </run>
            </image>
        </images>
    </configuration>
    <executions>
        <execution>
            <id>docker:build</id>
            <phase>package</phase>
            <goals>
                <goal>build</goal>
            </goals>
        </execution>
        <execution>
            <id>docker:start</id>
            <phase>install</phase>
            <goals>
                <goal>start</goal>
            </goals>
        </execution>
    </executions>
</plugin>

Each image configuration has three parts:

Image name and alias

<build> that defines how the image is created. Base image, build artifacts and their dependencies, ports to be exposed, etc to be included in the image are specified here.Assembly descriptor format is used to specify the artifacts to be included and is defined in src/main/docker directory. assembly.xml in our case looks like:

<assembly . . .>
  <id>javaee7-docker-maven</id>
  <dependencySets>
    <dependencySet>
      <includes>
        <include>org.javaee7.sample:javaee7-docker-maven</include>
      </includes>
      <outputDirectory>/opt/jboss/wildfly/standalone/deployments/</outputDirectory>
      <outputFileNameMapping>javaee7-docker-maven.war</outputFileNameMapping>
    </dependencySet>
  </dependencySets>
</assembly>