MyHelloWorld Dockerized

This guide shows how to set up a maven project that automatically builds a docker image for a Java application and pushes it to docker hub repository.

Pre requisites

Create your Repository on Docker Hub

create an account
create a private repository

Follow the official guide in case you have difficulties in process.

In this guide I'll use my private repository: adarko22/tutorial

Maven Plugins

In order to build and push to your repo the image for your Java application you first need to:

create a Jar with all the dependencies required to run your application; for this task maven-assembly-plugin is ideal!
create the image with a Dockerfile and push it to your repo; the dockerfile-maven-plugin is what we need!

maven-assembly-plugin

The Assembly Plugin for Maven enables to combine the project output into a single distributable archive that also contains dependencies, modules, site documentation, and other files. The plugin is easy to configure, see my-hello-world pom.xml, the most important property is your application's main class.

dockerfile-maven-plugin

todo add some info We'll be using Authentication with maven settings.xml.

todo specify how to configure:

contextDirectory
repository
tag
useMavenSettingsForAuth & authentication via settings.xml

authentication

add to settings.xml:

<pluginGroups>
    <pluginGroup>com.spotify</pluginGroup>
</pluginGroups>

<server>
    <id>docker.io</id>
    <username>FOO</username>
    <password>BAR</password>
</server>

Deploying

mvn clean install -Dmaven.deploy.skip to deploy only Docker images (default deploy phase is skipped)

This is necessary because we haven't configured any distribution management for maven default deploy (see Distribution Management

In case something goes wrong try to:

logout from docker: docker logout
delete config.json: rm ~/.docker/config.json
restart docker: service docker restart
login into docker using your docker.io credentials: docker login docker.io

Running the image

Once deployed the image is available in the local repository; verify it with:

docker images

In my case the output is:

REPOSITORY           TAG              IMAGE ID       CREATED         SIZE
adarko22/tutorial    my-hello-world   8ebfd19a3dc1   4 minutes ago   132MB

When running the image with:

docker run adarko22/tutorial:my-hello-world

The image is retrieved from the local repo. In order to get the image from the remote repo remove the image from the local repo with:

docker rmi -f 8ebfd19a3dc1

(where 8ebfd19a3dc1 is the image-id to remove); at this point the docker run command automatically pulls the image from the remote repo.

ADarko22/MyHelloWorldDockerized