This page handles creating and running a multi module project in Spring Boot.
It's based in the documentation provided by Spring:
https://spring.io/guides/gs/multi-module/
In the sample project there is a library jar and a main application that uses the library. You could also use it just to see how to build a library on its own (i.e. a jar file that is not an application).
1. Download sample code project
git clone https://github.com/spring-guides/draft-gs-multi-module.git
2. Go to the project
cd draft-gs-multi-module/complete/
3. Run the application
./mvnw install && ./mvnw spring-boot:run -pl application
4. Test the application
http://localhost:8080/