getting ready for docker deployment

docker-compose.yaml

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+version: '3.8'
+
+services:
+  # --- 1. Spring API Service (Backend) ---
+  spring-api:
+    build:
+      context: ./backend # Path to your Spring project's root folder
+      dockerfile: Dockerfile # Assumes you have a Dockerfile in ./backend
+    container_name: spring-api
+    ports:
+      - "8080:8080" # Map host port 8080 to container port 8080
+    environment:
+      # These environment variables link the API to the database service defined below
+      - SPRING_DATASOURCE_URL=jdbc:postgresql://db:5432/mydatabase
+      - SPRING_DATASOURCE_USERNAME=myuser
+      - SPRING_DATASOURCE_PASSWORD=mypassword
+    depends_on:
+      - db
+    networks:
+      - app-network
+
+  # --- 2. Next.js App Service (Frontend) ---
+  nextjs-app:
+    build:
+      context: ./frontend # Path to your Next.js project's root folder
+      dockerfile: Dockerfile # Assumes you have a Dockerfile in ./frontend
+    container_name: nextjs-app
+    ports:
+      - "3000:3000" # Map host port 3000 to container port 3000
+    environment:
+      # This variable is crucial: Next.js needs the URL for the Spring API
+      # Use the Docker internal service name 'spring-api' and its port 8080
+      - NEXT_PUBLIC_API_URL=http://spring-api:8080
+      # For local testing, you might need the host IP for Next.js to call back
+      # - NEXT_PUBLIC_API_URL_LOCAL=http://localhost:8080
+    depends_on:
+      - spring-api
+    networks:
+      - app-network
+
+  # --- 3. PostgreSQL Database Service (Example Dependency) ---
+  db:
+    image: postgres:15-alpine # Lightweight and stable PostgreSQL image
+    container_name: postgres-db
+    environment:
+      - POSTGRES_DB=mydatabase
+      - POSTGRES_USER=myuser
+      - POSTGRES_PASSWORD=mypassword
+    volumes:
+      - postgres_data:/var/lib/postgresql/data # Persist the database data
+    ports:
+      - "5432:5432" # Optional: Map DB port for external access (e.g., DBeaver)
+    networks:
+      - app-network
+
+# --- Docker Volume for Persistent Data ---
+volumes:
+  postgres_data:
+
+# --- Docker Network for Inter-Container Communication ---
+networks:
+  app-network:
+    driver: bridge