Moving a Spring Boot application's deployment process to Docker means replacing direct JAR execution on a server with building a container image and running it through Docker commands or an orchestrator, changing how the application is packaged, configured, and scaled.
Key Points: • Write a Dockerfile describing the base image and how the built JAR is packaged and started. • Replace manual server deployment scripts with docker build and docker push steps in the CI/CD pipeline. • Externalize configuration through environment variables instead of environment-specific property files baked into the artifact. • Introduce Docker Compose for local multi-container development, or Kubernetes for production orchestration, scaling, and self-healing. • Update health checks and logging to container-friendly patterns, like stdout logging and HTTP health check endpoints for the orchestrator to poll.
Example: Instead of SCP-ing a JAR to a server and restarting a systemd service, the CI pipeline now builds a Docker image, pushes it to a registry, and a Kubernetes deployment rolls out the new image with zero-downtime rolling updates.
Interview Tip: A concise interview answer is:
"I'd introduce a Dockerfile to package the app as an image, move configuration to environment variables, and update the CI/CD pipeline to build and push images instead of copying JAR files to servers. Then I'd run it through Docker Compose locally or Kubernetes in production, which gives me rolling updates, scaling, and self-healing that manual deployment didn't."