README

This is a very basic spring boot application containerized with docker to illustrate how we can create a micro service and deploy it with docker.

The application consists of two services, the Database and the API so it will create to different containers.

• The Database container is created from the official MySQL Docker image mysql:5.7.29
• The API container is created from a custom image which is assembled from a Dockerfile

API Container

The API's container image is assembled from the following Dockerfile

FROM maven:3.5.4-jdk-8-alpine AS MAVEN_BUILD
COPY pom.xml /build/
COPY src /build/src/
WORKDIR /build/
RUN mvn package -DskipTests
FROM openjdk:8-jre-alpine
WORKDIR /app
COPY --from=MAVEN_BUILD /build/target/hello-docker-0.0.1-SNAPSHOT.jar /app/
ENTRYPOINT ["java", "-jar", "hello-docker-0.0.1-SNAPSHOT.jar"]

What is this Dockerfile doing?

1. Pulls the maven:3.5.2-jdk-8-alpine image from docker-hub and starts the container. This is an image of alpine linux with maven installed
2. Copies the src folder and pom.xml file from the local working directory
3. Executes the mvn package command. This will download all project's dependencies, compile the code and create the hello-docker-0.1.0.jar file
4. Pulls the openjdk:8-jre-alpine image from docker-hub and starts the container. This is an image for alpine linux with openjdk installed
5. Copies the generated hello-docker-0.0.1-SNAPSHOT.jar from maven container to /app/ of jdk container
6. Finally executes the command java -jar hello-docker-0.0.1-SNAPSHOT.jar which actually starts the application

Database Container

Database container started from the official mysql:5.7.29 docker image

How the whole application works

To make the whole application functional we have to compose it with docker-compose command, docker-compose command runs multi-container applications with Docker as they are defined in a docker-compose.yml file. Our application uses the following docker-compose.yml which defines two services the mysql and the api. Each service has its own enviroment variables and ports mapping.

version: '3.7'
services:
    mysql:
        image: mysql:5.7.19
        container_name: Database
        restart: always
        environment:
          MYSQL_ROOT_PASSWORD: rootPassword
          MYSQL_DATABASE: tododb
          MYSQL_USER: todoUser
          MYSQL_PASSWORD: todoPassword        
#        volumes:
#            - db_data:/var/lib/mysql
        ports:
            - 3307:3306
    api:
        build: .
        container_name: API
        depends_on:
            - mysql
        environment:
            - SPRING_DATASOURCE_URL=jdbc:mysql://mysql:3306/tododb?useUnicode=true&characterEncoding=utf8&useSSL=false
            - SPRING_DATASOURCE_USERNAME=todoUser
            - SPRING_DATASOURCE_PASSWORD=todoPassword
            - SPRING_JPA_HIBERNATE_DDL-AUTO=create-drop
            - APP_MYVARIABLE=Hello from docker
        ports:
            - 9090:9090
#volumes:
#    db_data: {}

How to build

Download the project or better clone it

git clone git@github.com:mxaris/hello-docker.git

Inside the project's folder compose it with the following command:

docker-compose up

How to test

Open the following URL in your browser, you must see a list of todos

http://localhost:9090/todos

with curl

curl http://localhost:9090/todos | json_pp

Create a new todo

curl --header "Content-Type: application/json" -X POST -d '{"title":"Atlas dockerization","todo":"we must make Atlas dockerized"}' http://localhost:9090/todos | json_pp

Further testing

Make changes to the source code (eg add a new http request mapping in TodosController) and run the application with --build api option to rebuild the API's image

docker-compose up --build