version: "3.7"
services:
  api_service:
    build: .
    restart: always
    ports:
      - 8080:8080
    depends_on:
      - postgres_db
    links:
      - postgres_db:database
  postgres_db:
    image: "postgres:11.4"
    restart: always
    ports:
      - 5435:5432
    environment:
      POSTGRES_DB: testDb
      POSTGRES_PASSWORD: admin

this is my yaml

and I got properties

spring.datasource.platform=postgres
spring.datasource.url=jdbc:postgresql://database:5432/testDb
spring.datasource.username=postgres
spring.datasource.password=admin

if my postgres is rds then do I need to compose them or I just can go with dockerfile for jar only and not yaml file?

>Solution :

You can create environment variables for the RDS address, RDS username, RDS password and RDS port. Pass it to the Dockerfile to the api_service. Your api_service should know to assemble Postgres connection string based on the environment variables. Please check – Spring Profiles in connection String