Data Layer

Goal

This snapshot advances Ironclad Gazette by teaching you to persist authors and posts with JPA and MySQL.

Every numbered folder is a complete app. Run this stage independently, then compare it with the previous folder.

Prerequisites

Use Java 17+, Maven, a terminal, and Docker for MySQL stages. You should recognize classes, annotations, and HTTP verbs.

Port 8080 must be free. Copy .env.example before starting database stages.

• Java 17 and Maven
• A code editor and terminal
• Docker from part 4 onward

Concepts

JPA entities map to tables. Each snapshot uses its own ironclad database so stages stay independent.

Keep controllers thin: accept input, delegate to repositories or services, and let Thymeleaf escape output by default.

Walkthrough

Connect with JDBC URL, create User and Post entities, seed Ada and Grace, and list posts on the home page.

Read the example, then open the matching snapshot. The repository includes the surrounding setup and error handling.

@Entity
public class Post {
  @Id @GeneratedValue
  private Long id;
  private String title;
}

Run and verify

Enter 04-Data-Layer, start MySQL when needed, copy .env.example, and run mvn spring-boot:run on port 8080.

Open http://127.0.0.1:8080. Watch the terminal for validation and database errors.

docker compose -f ../docker-compose.yml up -d
git clone https://github.com/michaeldunga1/fcc-spring-blog.git
cd fcc-spring-blog/04-Data-Layer
cp .env.example .env
mvn spring-boot:run

Troubleshooting

Communications link failure usually means Docker MySQL is stopped or the port is not 3308.

Connection refused usually means Docker MySQL is stopped or the port is not 3308. For auth issues, confirm you are using email (not username) on the login form.

• Read the first error first
• Restart after environment changes
• Never commit .env or uploads

Try this

Add a minimum title length check before insert.

Test a happy path and one invalid or unauthorized request.

• Make one small change
• Test it in the browser
• Compare with the next snapshot only after it works