A CockroachDB Spring Boot Demo using Spring Data JDBC for data access.
Spring Data JDBC provides a simpler, yet powerful model than JPA or any other ORM frameworks. It's considered a good fit for data access logic that doesn't involve large, complex domain model mapping or any of the advanced features of JPA, such as lazy loading, second level caching, auto-batching and transparent persistence.
The JDBC demo has most code comments and also provides a few extra features compared to the other modules.