Dockerizing & Deploying Spring Boot

# Stage 1: Extract layers from the Spring Boot fat JAR
FROM eclipse-temurin:21-jre-alpine AS builder
WORKDIR /app
COPY target/*.jar app.jar
RUN java -Djarmode=layertools -jar app.jar extract

# Stage 2: Final minimal image
FROM eclipse-temurin:21-jre-alpine

# Security: run as non-root
RUN addgroup -S spring && adduser -S spring -G spring
USER spring:spring

WORKDIR /app

# Copy layers in order of least-to-most frequently changing
# (maximizes Docker cache reuse)
COPY --from=builder /app/dependencies/           ./
COPY --from=builder /app/spring-boot-loader/     ./
COPY --from=builder /app/snapshot-dependencies/  ./
COPY --from=builder /app/application/            ./

EXPOSE 8080

HEALTHCHECK --interval=30s --timeout=3s \
  CMD wget -qO- http://localhost:8080/actuator/health || exit 1

ENTRYPOINT ["java", "org.springframework.boot.loader.launch.JarLauncher"]

version: "3.9"
services:
  api:
    build: .
    ports: ["8080:8080"]
    environment:
      SPRING_PROFILES_ACTIVE: prod
      SPRING_DATASOURCE_URL: jdbc:postgresql://postgres:5432/mydb
      SPRING_DATASOURCE_USERNAME: postgres
      SPRING_DATASOURCE_PASSWORD: ${DB_PASSWORD}
      APP_SECURITY_JWT_SECRET: ${JWT_SECRET}
    depends_on:
      postgres:
        condition: service_healthy
    restart: unless-stopped

  postgres:
    image: postgres:16-alpine
    environment:
      POSTGRES_DB: mydb
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: ${DB_PASSWORD}
    volumes:
      - pg_data:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 10s
      timeout: 5s
      retries: 5

volumes:
  pg_data:

# Build JAR
mvn clean package -DskipTests

# Build Docker image
docker build -t my-api:1.0.0 .

# Run with Docker Compose
docker-compose up -d

# View logs
docker-compose logs -f api

# Spring Boot Buildpacks (no Dockerfile needed!)
mvn spring-boot:build-image -Dspring-boot.build-image.imageName=my-api:1.0.0