This repository is a Spring Boot training/courseware package rather than a production service. It consists of five independent, runnable Spring Boot applications under com.kousenit (demo, restclient, persistence, shopping, springai), accompanied by lab workbooks (labs.md, advanced-labs.md), course slides (slides.md), and CI workflows. The code demonstrates current-generation Spring and Spring Boot patterns: MVC and REST controllers, Java records for DTOs, RestClient and HTTP interfaces, JdbcClient and JPA data access, AOP aspects, RFC 7807 exception handling, and Spring AI chat clients. Although the dominant character is application code, it is educational example code, not a deployed system.