[101] Quickstart Containerized Java application

This repository is a quickstart guide for building a simple Java SpringBoot application into a container image using Gradle, maven-jib-plugin. Local tests are enabled by Docker & Minikube.

What you will need?

• Some Software Development experience with Java, Docker, Kubernetes
• Java 11+
• Gradle 7+
• Docker (for local build)
• Minikube (for local testing)
• A Github public repo (for CI)

What you will learn?

1. Build: Build a container image for a Java Springboot app using maven-jib-plugin
2. Run: Run the container image in Kubernetes (Minikube), Gotchas in the Minikube / Docker setup
3. Github Workflows: build container image, publish Junit test results as Artifacts

Quickstart

Build

Build JAR file & run Junit tests

./gradlew clean test

Build Container Image (using Docker)

./gradlew clean test jibDockerBuild

Build Container Image (for CI/CD pipelines)

./gradlew clean test jib

Run

Minikube / Docker

# !! Important Note !!
# Minikube comes with its own docker daemon and won't be able to find your local images by default

# 1. Start afresh
minikube delete
minikube start --driver=docker

# 2. Set environment variables (this is important)
eval $(minikube docker-env)

# 3. Build the container image
./gradlew clean test jibDockerBuild

# 4. Create deployment
kubectl run novarasa-java-pod --image=novarasa/quickstart-java-springboot --image-pull-policy=Never

# 5. See status of deployment & pods
kubectl get pods

# 5. On a separate terminal (to launch the Dashboard)
minikube dashboard

Changes required in an Enterprise setup

Within an Enterprise, you wouldn't typically be directly using the online Maven Repository (or) Docker Hub to pull / push artifacts. So some modifications to the gradle configurations will be required.

• gradle/gradle-wrapper.properties - amend distributionUrl to point to Gradle distributions available in your enterprise's artifact repository (JFrog Artifactory / Sonatype Nexus)
• build.gradle - jib.from.image jib.to.image should point to fully qualified paths in your enterprise's container registry and jib.from.auth jib.to.auth should the developer / API credentials used to pull / push images. Do not hardcode credentials instead pass them as environment variables from your CI pipeline.

References

• https://github.com/claudioaltamura/springboot-jib-helloworld
• https://spring.io/guides/gs/testing-web/
• https://github.com/marketplace/actions/publish-unit-test-results
• actions/starter-workflows#171 (gradlew chmod)
• https://medium.com/bb-tutorials-and-thoughts/how-to-use-own-local-doker-images-with-minikube-2c1ed0b0968