TP12.1 - Complete Dockerization

Objectives of the Lab

In this lab, you will:

✅ Create an optimized multi-stage Dockerfile
✅ Configure Docker Compose with PostgreSQL
✅ Manage profiles and configurations
✅ Test the application in a container

Estimated duration: 1h30

Context

You are dockerizing a task management application (Todo App) with a PostgreSQL database.

Part 1: Project Structure

todo-app/
├── src/
│   └── main/
│       ├── java/com/example/todo/
│       │   ├── TodoApplication.java
│       │   ├── entity/Todo.java
│       │   ├── repository/TodoRepository.java
│       │   ├── service/TodoService.java
│       │   └── controller/TodoController.java
│       └── resources/
│           ├── application.properties
│           ├── application-dev.properties
│           ├── application-docker.properties
│           └── application-prod.properties
├── pom.xml
├── Dockerfile
├── docker-compose.yml
├── docker-compose.prod.yml
└── .dockerignore

Part 2: The Application

Todo Entity

@Entity
@Table(name = "todos")
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Todo {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @NotBlank
    private String title;
    
    private String description;
    
    private boolean completed = false;
    
    @Column(name = "created_at")
    private LocalDateTime createdAt = LocalDateTime.now();
}

TodoController

@RestController
@RequestMapping("/api/todos")
@RequiredArgsConstructor
public class TodoController {

    private final TodoService todoService;

    @GetMapping
    public List<Todo> getAll() {
        return todoService.findAll();
    }

    @GetMapping("/{id}")
    public Todo getById(@PathVariable Long id) {
        return todoService.findById(id);
    }

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public Todo create(@Valid @RequestBody Todo todo) {
        return todoService.create(todo);
    }

    @PutMapping("/{id}")
    public Todo update(@PathVariable Long id, @Valid @RequestBody Todo todo) {
        return todoService.update(id, todo);
    }

    @PatchMapping("/{id}/toggle")
    public Todo toggle(@PathVariable Long id) {
        return todoService.toggleComplete(id);
    }

    @DeleteMapping("/{id}")
    @ResponseStatus(HttpStatus.NO_CONTENT)
    public void delete(@PathVariable Long id) {
        todoService.delete(id);
    }
}

Part 3: Configuration Files

application.properties

spring.application.name=todo-app

# Default profile
spring.profiles.active=${SPRING_PROFILES_ACTIVE:dev}

# Actuator
management.endpoints.web.exposure.include=health,info
management.endpoint.health.show-details=always

application-dev.properties

# H2 for local development
spring.datasource.url=jdbc:h2:mem:tododb
spring.datasource.driver-class-name=org.h2.Driver
spring.h2.console.enabled=true

spring.jpa.hibernate.ddl-auto=create-drop
spring.jpa.show-sql=true

logging.level.com.example=DEBUG

application-docker.properties

# PostgreSQL via Docker Compose
spring.datasource.url=jdbc:postgresql://db:5432/tododb
spring.datasource.username=todouser
spring.datasource.password=todopass
spring.datasource.driver-class-name=org.postgresql.Driver

spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=false
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.PostgreSQLDialect

logging.level.com.example=INFO

application-prod.properties

# Production - use environment variables
spring.datasource.url=${DATABASE_URL}
spring.datasource.username=${DB_USERNAME}
spring.datasource.password=${DB_PASSWORD}

spring.jpa.hibernate.ddl-auto=validate
spring.jpa.show-sql=false

logging.level.root=WARN
logging.level.com.example=INFO

# Security
server.error.include-stacktrace=never
management.endpoints.web.exposure.include=health,info,prometheus

Part 4: Dockerfile

Dockerfile

# ===== STAGE 1: Build =====
FROM maven:3.9-eclipse-temurin-17 AS builder

WORKDIR /app

# Copy pom.xml and download dependencies (cache)
COPY pom.xml .
RUN mvn dependency:go-offline -B

# Copy source code
COPY src ./src

# Compile the application
RUN mvn clean package -DskipTests

# ===== STAGE 2: Runtime =====
FROM eclipse-temurin:17-jre-alpine

WORKDIR /app

# Create a non-root user
RUN addgroup -S appgroup && adduser -S appuser -G appgroup

# Create the logs directory
RUN mkdir -p /app/logs && chown -R appuser:appgroup /app

# Switch to non-root user
USER appuser:appgroup

# Copy the JAR from the builder
COPY --from=builder /app/target/*.jar app.jar

# Expose the port
EXPOSE 8080

# Default environment variables
ENV JAVA_OPTS="-Xms256m -Xmx512m"
ENV SPRING_PROFILES_ACTIVE="docker"

# Health check
HEALTHCHECK --interval=30s --timeout=3s --start-period=60s --retries=3 \
  CMD wget --quiet --tries=1 --spider http://localhost:8080/actuator/health || exit 1

# Launch the application
ENTRYPOINT ["sh", "-c", "java $JAVA_OPTS -jar app.jar"]

Part 5: Docker Compose

docker-compose.yml (Development)

version: '3.8'

services:
  app:
    build:
      context: .
      dockerfile: Dockerfile
    container_name: todo-app
    ports:
      - "8080:8080"
    environment:
      - SPRING_PROFILES_ACTIVE=docker
    depends_on:
      db:
        condition: service_healthy
    networks:
      - todo-network
    restart: unless-stopped

  db:
    image: postgres:15-alpine
    container_name: todo-db
    environment:
      POSTGRES_DB: tododb
      POSTGRES_USER: todouser
      POSTGRES_PASSWORD: todopass
    volumes:
      - postgres_data:/var/lib/postgresql/data
    ports:
      - "5432:5432"
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U todouser -d tododb"]
      interval: 10s
      timeout: 5s
      retries: 5
    networks:
      - todo-network

  # Optional: PgAdmin to manage the DB
  pgadmin:
    image: dpage/pgadmin4:latest
    container_name: todo-pgadmin
    environment:
      PGADMIN_DEFAULT_EMAIL: admin@example.com
      PGADMIN_DEFAULT_PASSWORD: admin
    ports:
      - "5050:80"
    depends_on:
      - db
    networks:
      - todo-network

volumes:
  postgres_data:

networks:
  todo-network:
    driver: bridge

docker-compose.prod.yml

version: '3.8'

services:
  app:
    image: ${DOCKER_IMAGE:-todo-app:latest}
    container_name: todo-app-prod
    ports:
      - "8080:8080"
    environment:
      - SPRING_PROFILES_ACTIVE=prod
      - DATABASE_URL=${DATABASE_URL}
      - DB_USERNAME=${DB_USERNAME}
      - DB_PASSWORD=${DB_PASSWORD}
      - JAVA_OPTS=-Xms512m -Xmx1024m
    deploy:
      resources:
        limits:
          cpus: '1'
          memory: 1G
        reservations:
          cpus: '0.5'
          memory: 512M
    restart: always
    logging:
      driver: json-file
      options:
        max-size: "10m"
        max-file: "3"

Part 6: .dockerignore

# Build output
target/
!target/*.jar

# IDE
.idea/
*.iml
.vscode/
*.swp

# Git
.git/
.gitignore

# Docker files
Dockerfile*
docker-compose*.yml
.dockerignore

# Logs
*.log
logs/

# Tests
src/test/

# Documentation
*.md
docs/

# Secrets (never include them!)
.env
*.pem

Part 7: Tests

Build and Run

# 1. Build the image
docker-compose build

# 2. Start the services
docker-compose up -d

# 3. Check the logs
docker-compose logs -f app

# 4. Check health
curl http://localhost:8080/actuator/health

Test the API

# Create a todo
curl -X POST http://localhost:8080/api/todos \
  -H "Content-Type: application/json" \
  -d '{"title": "Learn Docker", "description": "Containerize Spring Boot"}'

# List todos
curl http://localhost:8080/api/todos

# Toggle complete
curl -X PATCH http://localhost:8080/api/todos/1/toggle

# Delete
curl -X DELETE http://localhost:8080/api/todos/1

Access PgAdmin

Open http://localhost:5050
Login: admin@example.com / admin
Add Server:
- Host: db
- Port: 5432
- Username: todouser
- Password: todopass

Part 8: Useful Commands

# See containers
docker-compose ps

# See logs
docker-compose logs -f

# Stop everything
docker-compose down

# Stop and remove volumes
docker-compose down -v

# Rebuild without cache
docker-compose build --no-cache

# Run a shell in the container
docker exec -it todo-app sh

# See image sizes
docker images | grep todo

Final Verification

Checklist

docker-compose up starts without error
The app responds on http://localhost:8080
/actuator/health returns UP
The PostgreSQL DB is connected
Todos are persisted (restart OK)
The image is less than 300 MB

Check Image Size

docker images todo-app
# REPOSITORY   TAG       SIZE
# todo-app     latest    ~180MB

🎯 Next Step

➡️ TP12.2: CI/CD Pipeline and Deployment

⬅️ Back to Module 12

Objectives of the Lab​

Context​

Part 1: Project Structure​

Part 2: The Application​

Todo Entity​

TodoController​

Part 3: Configuration Files​

application.properties​

application-dev.properties​

application-docker.properties​

application-prod.properties​

Part 4: Dockerfile​

Dockerfile​

Part 5: Docker Compose​

docker-compose.yml (Development)​

docker-compose.prod.yml​

Part 6: .dockerignore​

Part 7: Tests​

Build and Run​

Test the API​

Access PgAdmin​

Part 8: Useful Commands​

Final Verification​

Checklist​

Check Image Size​

🎯 Next Step​

Objectives of the Lab

Context

Part 1: Project Structure

Part 2: The Application

Todo Entity

TodoController

Part 3: Configuration Files

application.properties

application-dev.properties

application-docker.properties

application-prod.properties

Part 4: Dockerfile

Dockerfile

Part 5: Docker Compose

docker-compose.yml (Development)

docker-compose.prod.yml

Part 6: .dockerignore

Part 7: Tests

Build and Run

Test the API

Access PgAdmin

Part 8: Useful Commands

Final Verification

Checklist

Check Image Size

🎯 Next Step