How to Use Docker Compose with Spring Boot

To use docker-compose with a Spring Boot app, create a Dockerfile to containerize your app, then define services in a docker-compose.yml file specifying the image build and ports. Run docker-compose up to start your Spring Boot app inside a Docker container easily.

Syntax

The docker-compose.yml file defines services, networks, and volumes for your app. Key parts include:

• version: Compose file format version.
• services: Defines containers to run.
• build: Path to Dockerfile to build the image.
• ports: Maps container ports to host ports.

The Dockerfile describes how to build your Spring Boot app image, usually starting from a Java base image, copying the jar, and setting the startup command.

yaml

version: '3.8'
services:
  springboot-app:
    build: .
    ports:
      - "8080:8080"

Example

This example shows a simple Spring Boot app containerized with a Dockerfile and run using docker-compose.

plaintext

### Dockerfile
FROM eclipse-temurin:17-jdk-alpine
ARG JAR_FILE=target/*.jar
COPY ${JAR_FILE} app.jar
ENTRYPOINT ["java","-jar","/app.jar"]

---

### docker-compose.yml
version: '3.8'
services:
  springboot-app:
    build: .
    ports:
      - "8080:8080"

Output

Starting springboot-app ... done
Attaching to springboot-app
springboot-app | 2024-06-01 12:00:00.000  INFO 1 --- [           main] com.example.Application                  : Started Application in 3.5 seconds (JVM running for 4.0)

Common Pitfalls

Common mistakes include:

• Not exposing the correct port in docker-compose.yml (e.g., mapping wrong ports).
• Forgetting to build the jar before running docker-compose.
• Using an incorrect base image in the Dockerfile that doesn't support your Java version.
• Not setting the correct ENTRYPOINT or CMD to start the Spring Boot app.

yaml

### Wrong port mapping example
version: '3.8'
services:
  springboot-app:
    build: .
    ports:
      - "9090:8080"  # Host port 9090 mapped to container 8080

### Correct port mapping example
version: '3.8'
services:
  springboot-app:
    build: .
    ports:
      - "8080:8080"

Quick Reference

Tips for using Docker Compose with Spring Boot:

• Always build your jar with ./mvnw clean package before building the Docker image.
• Use a lightweight Java base image like eclipse-temurin:17-jdk-alpine for smaller images.
• Map container port 8080 to a host port to access your app in the browser.
• Use docker-compose up --build to rebuild images when code changes.

Key Takeaways

Create a Dockerfile to containerize your Spring Boot app with a Java base image and jar copy.

Define your app service in docker-compose.yml with build context and port mapping.

Run your app using docker-compose up to start the container easily.

Ensure ports are correctly mapped and the jar is built before running containers.

Use docker-compose up --build to rebuild images after code changes.