Spring Boot, Docker and MySQL

Architecture

flowchart LR
    A[Spring Boot Container] -->|JDBC| B[(MySQL Container)]
    C[MySQL Workbench] -->|Port 3306| B

Spring Boot Dockerfile

FROM eclipse-temurin:17-jdk-jammy

WORKDIR /app

COPY target/myapp.jar app.jar

EXPOSE 8080

ENTRYPOINT ["java","-jar","app.jar"]

Docker Compose

version: "3.8"

services:
  app:
    build: .
    container_name: springboot-app
    ports:
      - "8080:8080"
    depends_on:
      - mysql
    environment:
      SPRING_DATASOURCE_URL: jdbc:mysql://mysql:3306/coredb
      SPRING_DATASOURCE_USERNAME: root
      SPRING_DATASOURCE_PASSWORD: root

  mysql:
    image: mysql:8.0
    container_name: mysql-db
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: coredb
    ports:
      - "3306:3306"
    volumes:
      - mysqldata:/var/lib/mysql

volumes:
  mysqldata:

Why use mysql instead of localhost

Inside Docker, localhost refers to the current container.

flowchart LR
    A[Spring Container localhost] -.X.-> B[MySQL Container]
    A -->|mysql service name| B

Use:

spring.datasource.url=jdbc:mysql://mysql:3306/coredb

Not:

spring.datasource.url=jdbc:mysql://localhost:3306/coredb

Running

docker compose up --build

Detached mode:

docker compose up -d

Stop:

docker compose down

Remove volumes:

docker compose down -v

Automatic Database Creation

environment:
  MYSQL_ROOT_PASSWORD: root
  MYSQL_DATABASE: coredb

MYSQL_DATABASE automatically creates coredb the first time the MySQL data directory is initialized.

MySQL Workbench

Use these connection details:

Setting	Value
Host	localhost
Port	3306
Username	root
Password	root

If port 3306 is already in use, map another host port:

ports:
  - "3307:3306"

Then connect Workbench to port 3307.

Employee Table

CREATE TABLE employee (
    id BIGINT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(255),
    salary VARCHAR(255),
    version BIGINT
);

Insert sample data:

INSERT INTO employee (name, salary, version)
VALUES
('Abirami','50000',0),
('John','60000',0),
('Alice','70000',0);

View data:

SELECT * FROM employee;

Common Hibernate Error

Unable to determine Dialect without JDBC metadata

Possible causes:

• Wrong JDBC URL
• MySQL container not running
• Using localhost inside Docker
• Database not yet ready

Recommended property:

spring.jpa.database-platform=org.hibernate.dialect.MySQLDialect

(MySQL8Dialect was removed in Hibernate 6 / Spring Boot 3 — use MySQLDialect, or omit the property entirely and let Hibernate auto-detect the dialect from the JDBC connection.)

Best Practices

• Use Docker Compose for application + database.
• Use named volumes for persistence.
• Use MySQL Workbench as the desktop client.
• Avoid mixing host databases with containerized applications.

Key Takeaways

• Docker Compose creates networking automatically.
• Use the Compose service name as the database host.
• MYSQL_DATABASE creates the database on first initialization.
• MySQL Workbench connects through the exposed host port.