Spring Boot

Capstone – Article 15: Dockerization & Deployment (Expense Tracker)

By Utility Zone · 2026-01-27T18:33:49.370299

1. Introduction

You’ve built a complete, secure, production-ready backend. Now it’s time to package and deploy it like real applications.

In this article, you will:

  • Dockerize the Expense Tracker
  • Run it as a container
  • Prepare it for cloud deployment

This is the final technical milestone of the capstone.

2. Why Docker Matters

Docker allows you to:

  • Package app + runtime together
  • Eliminate environment issues
  • Deploy consistently across platforms

In industry: ✔ Almost all Spring Boot apps are containerized

3. Creating a Dockerfile

Create a file named Dockerfile in the project root.

3.1 Recommended Dockerfile

FROM eclipse-temurin:17-jdk-alpine
VOLUME /tmp
ARG JAR_FILE=target/expense-tracker-0.0.1-SNAPSHOT.jar
COPY ${JAR_FILE} app.jar
ENTRYPOINT ["java","-jar","/app.jar"]

Why this works:

  • Small image
  • Java 17 compatible
  • Fast startup

4. Adding .dockerignore

Create .dockerignore:

target/
.git
.gitignore
README.md

This reduces image size and speeds up builds.

5. Building the Docker Image

First, build the JAR:

mvn clean package

Then build the image:

docker build -t expense-tracker:1.0 .

6. Running the Container Locally

docker run -p 8080:8080 expense-tracker:1.0

Verify:

http://localhost:8080/actuator/health

App should be UP.

7. Passing Environment Variables

Example:

docker run -p 8080:8080   -e SPRING_PROFILES_ACTIVE=prod   -e JWT_SECRET=secure-secret   expense-tracker:1.0

Spring Boot automatically reads these.

8. Preparing for Cloud Deployment

Before deploying: ✔ Externalize configuration
✔ Secure secrets
✔ Disable Swagger in prod
✔ Use Actuator health check

9. Deployment Options

Beginner-friendly:

  • Render
  • Railway

Enterprise:

  • AWS (Elastic Beanstalk / ECS)
  • Azure
  • GCP

All support Docker-based deployment.

10. Deploying to Render (Example)

Steps:

  1. Push code to GitHub
  2. Create new Web Service on Render
  3. Select Docker
  4. Set environment variables
  5. Deploy

You’ll get a public URL.

11. Common Deployment Issues

❌ App fails due to missing env vars
❌ Port mismatch
❌ Insufficient memory
❌ DB connectivity issues

Always check:

  • Logs
  • Health endpoint

12. Git Commit (Important)

git add .
git commit -m "Dockerize expense tracker and prepare for deployment"

13. What You Should Have Now

At this point:

  • App runs in Docker
  • Configuration is externalized
  • Ready for cloud deployment

You now have a real production backend.

14. What’s Next?

➡ Capstone – Final Article: Project Wrap-Up & Interview Readiness

  • How to explain this project
  • Resume & interview tips
  • Next learning steps

Type Next when you’re ready 🎯🚀