I have created an example project for migrating an OSGI-based Spring Boot application into a standalone application (in the „Maven“ branch):
The application runs in the JVM of the Notes Client, only a user id is required, not a complete server installation (and ID). The benefit is that you can run as much JVM instances you want (which allows a better resource management and deployment) and it is easier to integrate the applications into existing CD environments. Also, Non-Domino developers can use their preferred IDE and are able to use existing / standard knowledge when developing Java applications.
When using the Java NAPI, you need to remove the spring-boot-devtools dependency because of problems with the class loader and Domino-specific DLLs.