🚀 Docker Multi-Stage Builds with Java (Spring Boot)

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Welcome to the official repository for exploring Docker Multi-Stage Builds with a real-world Spring Boot example! This project demonstrates how to optimize Docker image size and performance using a two-stage build process.

🔗 Live Blog Post: Docker Multi-Stage Builds Demystified
📦 Repo URL: https://github.com/moshclouds/Docker-multi-stage-builds

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📁 Project Structure

moshclouds-docker-multi-stage-builds/
├── Dockerfile                  # Multi-stage Docker build file
├── pom.xml                     # Maven project descriptor
├── .dockerignore              # Excludes unnecessary files from Docker context
├── mvnw, mvnw\.cmd              # Maven wrapper for consistent builds
├── src/
│   ├── main/java               # Application source code
│   ├── resources/             # Configuration (e.g., application.properties)
│   └── test/java              # Unit tests
└── .mvn/wrapper               # Maven wrapper properties

🛠️ Multi-Stage Dockerfile Explained

This project uses two stages in the Dockerfile:

🔨 Stage 1: Build the Application

FROM maven:3.9.6-eclipse-temurin-21 as build
WORKDIR /app
COPY pom.xml .
RUN mvn dependency:go-offline
COPY src ./src
RUN mvn clean package -DskipTests

• Image: Uses official Maven with JDK 21
• Caching: Downloads dependencies before copying source to cache Maven layers
• Result: Compiles the project and packages it into a .jar

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🚀 Stage 2: Run the Application

FROM eclipse-temurin:21-jdk-alpine
WORKDIR /app
COPY --from=build /app/target/*.jar app.jar
EXPOSE 8890
ENTRYPOINT ["java", "-jar", "app.jar"]

• Image: Lightweight Alpine with JDK 21
• Copy: Only the JAR from the build stage is added
• Runtime: Starts the Spring Boot app with exposed port 8890

✅ Result: Smaller, secure, and production-optimized Docker image

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🧪 Run the Project Locally

Step 1: Build the Docker Image

docker build -t moshclouds/multi-stage-app .

Step 2: Run the Container

docker run -p 8890:8890 moshclouds/multi-stage-app

🧭 Visit: http://localhost:8890/ You should see: Server is up and running 🚀

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✨ Why Multi-Stage Builds?

• ✅ Smaller Image Sizes
• ✅ Secure – no build tools in final image
• ✅ Clean separation of concerns
• ✅ Better CI/CD pipeline efficiency

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📌 Tech Stack

• Java 21
• Spring Boot
• Maven
• Docker

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📬 Contributing

If you'd like to contribute or enhance this project, feel free to fork the repo and make a pull request.

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