Dockerfile for Spring Boot in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of a Dockerfile in a Spring Boot project?

A Dockerfile defines the steps to create a Docker image that packages the Spring Boot application and its environment so it can run consistently anywhere.

beginner

Which base image is commonly used for building a Spring Boot Docker image?

OpenJDK base images like 'openjdk:17-jdk-slim' are commonly used because Spring Boot apps run on Java.

beginner

What command in a Dockerfile copies the Spring Boot jar file into the image?

The 'COPY' command copies files from your project into the Docker image, e.g., 'COPY target/app.jar app.jar'.

beginner

How do you specify the command to run the Spring Boot app inside the Docker container?

Use the 'ENTRYPOINT' or 'CMD' instruction with 'java -jar app.jar' to start the Spring Boot application.

intermediate

Why is it useful to use a multi-stage Dockerfile for Spring Boot?

Multi-stage builds separate building the jar and running it, making the final image smaller and faster to deploy.

Which Dockerfile instruction copies your Spring Boot jar into the image?

A COPY

B RUN

C ADD

D EXPOSE

COPY copies files from your local project into the Docker image.

What base image is best for running a Spring Boot app with Java 17?

A openjdk:17-jdk-slim

B node:latest

C python:3.12

D ubuntu:20.04

openjdk:17-jdk-slim provides Java 17 runtime needed for Spring Boot.

Which Dockerfile instruction sets the command to start the Spring Boot app?

A WORKDIR

B ENV

C CMD

D VOLUME

CMD or ENTRYPOINT defines the command to run inside the container.

Why use a multi-stage Dockerfile for Spring Boot?

A To build and run in one step

B To reduce final image size

C To add more layers

D To run multiple apps

Multi-stage builds keep the final image small by excluding build tools.

What does the EXPOSE instruction do in a Spring Boot Dockerfile?

A Sets environment variables

B Copies files

C Runs the app

D Declares the port the app listens on

EXPOSE tells Docker which port the container listens on.

Describe the key steps to create a Dockerfile for a Spring Boot application.

Think about how to package and run a Java app inside Docker.

Explain the benefits of using a multi-stage Dockerfile for Spring Boot projects.

Consider how to keep the Docker image small and efficient.