Hello Docker

A simple Spring Boot application demonstrating various Docker containerization approaches for Java applications.

Description

This project showcases how to containerize a Spring Boot application using different Docker strategies:

• Standard JAR-based containerization
• Multi-stage builds for optimized images
• GraalVM native image compilation for smaller footprint and faster startup

The application itself is a minimal REST API with a single endpoint:

• GET / - Returns the greeting message "Hello Docker 👋"

Prerequisites

• Java 21
• Docker
• Docker Compose
• Maven 3.9+ (or use the included Maven wrapper)

Getting Started

Clone the Repository

git clone https://github.com/buzzcosm/hello-docker.git
cd hello-docker

Build and Run Locally

./mvnw clean package
java -jar target/hello-docker.jar

The application will be available at http://localhost:8080

🐳 Docker Containerization Benchmark

🐳🔧 Dockerfile commands

• FROM initializes the build stage and defines the base image to build on.
• WORKDIR sets the working directory for any RUN, CMD, ENTRYPOINT, COPY, and ADD directives that follow in the Dockerfile.
• COPY copies new files or directories into the Docker image.
• RUN executes commands on top of the current image as a new layer and commits the results.
• EXPOSE configures Docker to open a specific network port for listening on the container, in this case port 8080.
• ENV sets environment variables.
• CMD provides the default execution command when the container is run.

🧪 Automated Build & Test Scripts

s. directory: scripts/build_and_test_image_v*.sh

This script will:

• Check if Docker is running
• Automatically build the image
• Start the container using docker-compose.yml
• Test the HTTP response for the string Hello Docker
• Print the result
• Stop and remove the container afterward

🧩(optional) Java containers with Jib

• Building Java containers with Jib

Helper - Get Digest if image:

docker inspect <image>:<tag> --format='{{index .RepoDigests 0}}'

Build Docker Image

./mvnw clean compile jib:dockerBuild

Test

docker run --platform linux/amd64 -it --rm -p 8080:8080 --name hello-docker-jib hello-docker:jib  

🧩(optional) Spring-Boot Container

• Packaging OCI Images

./mvnw spring-boot:build-image -Dspring-boot.build-image.imageName=hello-docker:spring-boot-build