Spring Boot with a MySQL Container

Running the Application

• git clone https://github.com/probstin/java-mysql-example.git && cd java-mysql-example
• cp mysql.env.EXAMPLE mysql.env
• Specify a MYSQL_PASSWORD for the created user: example_user
• Inspect te docker/mysql/init.sql file to see where the example_db is created and the example_user is granted permission.
• Open a terminal window: docker-compose up to start the MySQL container
• Open another terminal window: ./mvnw spring-boot:run -Dspring-boot.run.arguments="--spring.datasource.url=jdbc:mysql://127.0.0.1:3307/example_db --spring.datasource.username=example_user --spring.datasource.password=YOUR_PASSWORD_HERE"

The Configuration

docker-compose.yml

Contains a MySQL container that exposes port 3307 and forwards to 3306 internally, where the MySQL server is running. 3307 is used as the exposed port in the event you have a local running instance of a MySQL server - more than likely on 3306.

The db service within defines an env_file, titled mysql.env, that contains the sensitive environment variables captured in the mysql.env.EXAMPLE file. These variables will get loaded and applied by the MySQL container at runtime. See the official image documentation for more information and a complete list of environment variables.

The db service also defines a volume that loads in an entrypoint directory ./docker/mysql that contains an init.sql file that initializes an example database. The folder gets mounted to the container to /docker-entrypoint-initdb.d/ where it is then executed on startup.

mysql.env

Contains the sensitive environment variables captured in the mysql.env.EXAMPLE file. These variables will get loaded and applied by the MySQL container at runtime. See the official image documentation for more information and a complete list of environment variables. This file has been added to the .gitignore file and should not be committed!

Spring Datasource Properties

The application.properties file has been removed here to promote good hygeine when handling sensitive values. Instead, we can specify these at runtime by overriding the spring properties via the Maven Plugin command -Dspring-boot.run.arguments:

./mvnw spring-boot:run \
-Dspring-boot.run.arguments="--spring.datasource.url=jdbc:mysql://127.0.0.1:3307/example_db --spring.datasource.username=example_user --spring.datasource.password=YOUR_PASSWORD_HERE"

In a real application, you might look to parameterize the application.properties file.

init.sql

The docker/mysql/init.sql file contains SQL that is run by the MySQL container on startup. In this example, we are simply creating a database for the application to connect to and then granting the MYSQL_USER, defined in the mysql.env file, access to that database.