Follow this tutorial: https://spr.com/part-1-getting-started-again-build-a-web-app-with-spring-boot/
This application runs on port 8080 and have only 1 endpoint at /
You can check it by open terminal:
$ curl localhost:8080
Greetings from Spring Boot!
You can run it directly by running
java -jar gs-spring-boot-0.1.0.jar
Or modify and rebuild it with
./gradlew clean build
The jar file will be placed in /build/libs