Creating a container for a Vert.x app packaged as an executable uber-jar

What you will create

You will create a container for a Vert.x app packaged as an executable uber-jar.

The how-to consists in a couple of files:

1. the docker-maven/Dockerfile, for Maven users, or

2. the docker-gradle/Dockerfile, for Gradle users.

What you need

• A text editor or IDE

• Docker

Using Maven

Generate the project

First, generate the project from https://start.vertx.io:

1. Select the Maven build type

2. Set the artifactId to container-uber-jar

3. Select the JDK 11 JDK version

4. Click on generate and extract the content somewhere on your disk

Alternatively, open a terminal and run:

curl -G https://start.vertx.io/starter.zip -d "artifactId=container-uber-jar" -d "jdkVersion=11" -d "buildTool=maven" --output container-uber-jar.zip
unzip container-uber-jar.zip

Or, with HTTPie:

http https://start.vertx.io/starter.zip artifactId==container-uber-jar jdkVersion==11 buildTool==maven --output container-uber-jar.zip
unzip container-uber-jar.zip

Configuring the Docker build

At the root of the project, create a docker-maven/Dockerfile build file:

Docker build file for a Maven project

The Docker build has two stages:

1. Building the Maven project inside a maven:3.9.9-eclipse-temurin-11 container

2. Copying the output of the build in a eclipse-temurin:11 container and configuring the entry point

The benefits of this approach are:

• reproducible build: no matter who in the team runs the Docker build, it will always use the same Maven version and JDK version (both at build-time and run-time)

• small container image size: the final container will be based on a slim JDK image and will only add the uber-jar file

To build the container, open a terminal at the root of the project and run:

docker build -t com.example/container-uber-jar -f docker-maven/Dockerfile .

Using Gradle

Generate the project

First, generate the project from https://start.vertx.io:

1. Select the Gradle build type

2. Set the artifactId to container-uber-jar

3. Select the JDK 11 JDK version

4. Click on generate and extract the content somewhere on your disk

Alternatively, open a terminal and run:

curl -G https://start.vertx.io/starter.zip -d "artifactId=container-uber-jar" -d "jdkVersion=11" -d "buildTool=gradle" --output container-uber-jar.zip
unzip container-uber-jar.zip

Or, with HTTPie:

http https://start.vertx.io/starter.zip artifactId==container-uber-jar jdkVersion==11 buildTool==gradle --output container-uber-jar.zip
unzip container-uber-jar.zip

Configuring the Docker build

At the root of the project, create a docker-gradle/Dockerfile build file:

Docker build file for a Gradle project

The Docker build has two stages:

1. Building the Gradle project inside a gradle:8.1.1-jdk11 container

2. Copying the output of the build in a eclipse-temurin:11 container and configuring the entry point

The benefits of this approach are:

• reproducible build: no matter who in the team runs the Docker build, it will always use the same Gradle version and JDK version (both at build-time and run-time)

• small container image size: the final container will be based on a slim JDK image and will only add the uber-jar file

To build the container, open a terminal at the root of the project and run:

docker build -t com.example/container-uber-jar -f docker-gradle/Dockerfile .

Running the application

Now that you have built the container image, it is time to try it out!

Open a terminal and run:

docker run -p 8888:8888 com.example/container-uber-jar

You should see messages like these on the console output:

HTTP server started on port 8888
Dec 02, 2024 5:17:19 PM io.vertx.launcher.application.VertxApplication
INFO: Succeeded in deploying verticle

Then browse to http://localhost:8888 and get your greeting from the Vert.x app running in the container!

Summary

This document covered:

1. configuring a Docker build for Maven users,

2. configuring a Docker build for Gradle users.

See also

• Dockerfile reference

• Multi-stage builds introduction