Docker Compose + Spring Boot + Postgres connection

Question

I have a Java Spring Boot app which works with a Postgres database. I want to use Docker for both of them. I initially put just the Postgres in Docker, and I had a docker-

Answer 1

Each container has its own network interface with its own localhost. So change how Java points to Postgres:

spring.datasource.url=jdbc:postgresql://localhost:5432/sample

To:

spring.datasource.url=jdbc:postgresql://db:5432/sample

db will resolve to the proper Postgres IP.

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Bonus. With docker-compose you don't need to build your image by hand. So change:

web:
  image: myuser/manager:latest

To:

web:
  build: .