Docker Compose for Spring Boot application with PostgreSQL

In this blog post you will learn how to configure Spring Boot application with PostgreSQL for running with Docker Compose.

This blog post covers:

• Spring Boot application Dockerfile configuration with clean separation between dependencies and resources
• Docker Compose configuration for running the application with PostgreSQL

Prerequisites

• Docker
• Java 13
• Terminal
• httpie (or curl)

Application

• Generate the Maven based Spring Boot application with Spring Web, Spring Data JPA, Spring Data REST, PostgreSQL JDBC Driver dependencies.
• Add Testcontainers to use dockerized database in integration tests. You can read more about using Testcontainers with Spring Boot in this article: Spring Boot tests with Testcontainers and PostgreSQL, MySQL or MariaDB

The source code for this article can be found on Github: https://github.com/kolorobot/spring-boot-tc

Dockerfile

• Create Dockerfile
• Base Docker image uses Alpine Linux:

FROM openjdk:13-alpine

• Do not run the application as root:

RUN addgroup -S spring && adduser -S spring -G spring
USER spring:spring

• Do not deploy the fat-jar into the container, but rather split dependencies and application classes and resources into separate layers:

ARG DEPENDENCY=target/dependency
COPY ${DEPENDENCY}/BOOT-INF/lib /app/lib
COPY ${DEPENDENCY}/META-INF /app/META-INF
COPY ${DEPENDENCY}/BOOT-INF/classes /app

Note: ARG can be used to adjust the directory, in case you you have Gradle based project: docker build --build-arg DEPENDENCY=build/dependency -t spring-boot-tc .

• Run the application inside the containers by pointing the main class and the libs in the java command:

ENTRYPOINT ["java","-cp","app:app/lib/*","pl.codeleak.samples.springboot.tc.SpringBootTestcontainersApplication"]

The complete Dockerfile:

FROM openjdk:13-alpine
RUN addgroup -S spring && adduser -S spring -G spring
USER spring:spring
ARG DEPENDENCY=target/dependency
COPY ${DEPENDENCY}/BOOT-INF/lib /app/lib
COPY ${DEPENDENCY}/META-INF /app/META-INF
COPY ${DEPENDENCY}/BOOT-INF/classes /app
ENTRYPOINT ["java","-cp","app:app/lib/*","pl.codeleak.samples.springboot.tc.SpringBootTestcontainersApplication"]

New to Docker?  Docker explained in 12 minutes: https://www.youtube.com/watch?v=YFl2mCHdv24

Docker Compose

• Create docker-compose.yml
• We will have two services: db for PostgreSQL database and app for the application
  • db service will use the postgres image from a public repository, it will expose port 5432 to the host and it will pass the environment properties POSTGRES_* to the container to setup the database name, user and password.
  • app service will use the local build we created earlier, it will expose port 9000 to the host and it will pass the environment properties that will override the datasource configuration of the application (application.properties). The app service will depend on db service. The datasource URL uses the db as hostname which reflects the name of the db service.

The complete docker-compose.yml:

version: '3'

services:
  db:
    image: "postgres"
    ports:
      - "5432:5432"
    environment:
      POSTGRES_DB: tc
      POSTGRES_USER: tc
      POSTGRES_PASSWORD: tc
  app:
    build: .
    ports:
      - "9000:8080"
    environment:
      SPRING_DATASOURCE_URL: jdbc:postgresql://db/tc
      SPRING_DATASOURCE_USERNAME: tc
      SPRING_DATASOURCE_PASSWORD: tc
    depends_on:
      - db

New to Docker Compose? Docker Compose explained in 12 min: https://www.youtube.com/watch?v=Qw9zlE3t8Ko

Running the application

• Package the application

$ ./mvnw clean package

To skip the tests use: -DskipTests=true

• Extract libraries from fat-jar

$ mkdir -p target/dependency && (cd target/dependency; jar -xf ../*.jar)

• Run with docker-compose

$ docker-compose build && docker-compose up

• Verify the application is running and responding to requests

$ http get :9000/owners

HTTP/1.1 200
Connection: keep-alive

{
    "_embedded": {
        "owners": []
    },
    "_links": {
        "profile": {
            "href": "http://localhost:8080/profile/owners"
        },
        "self": {
            "href": "http://localhost:8080/owners{?page,size,sort}",
            "templated": true
        }
    },
    "page": {
        "number": 0,
        "size": 20,
        "totalElements": 0,
        "totalPages": 0
    }
}

Source code

The source code for this article can be found on Github: https://github.com/kolorobot/spring-boot-tc

References

• https://spring.io/guides/gs/spring-boot-docker/
• https://openliberty.io/blog/2018/06/29/optimizing-spring-boot-apps-for-docker.html

See also

• Spring Boot tests with Testcontainers and PostgreSQL, MySQL or MariaDB
• Spring Boot testing with JUnit 5
• macOS: essential tools for (Java) developer