Spring Boot Application

This one walks you through the standard Spring Boot stack with proper separation of concerns: JPA entities, Spring Data repositories, service layers, REST controllers, and Spring Security config. It's opinionated about doing things the Spring way, with dependency injection, transaction boundaries, and DTOs instead of exposing entities directly. The reference guides cover each layer separately, which is helpful if you're setting up a new project or teaching someone the architecture. Honest take: it's pretty comprehensive for the typical CRUD API with auth, but if you're already comfortable with Spring conventions, you might just need the security or JPA sections as a reference.