Use Link-1 to generate a project. this a basic project for learning. you can understand the folder structure. Use Link-2 for creating a basic Spring boot project. 1: http://start.spring.io/ 2: https://projects.spring.io/spring-boot/
Create a gradle/maven project Automatically src/main/java and src/main/test will be created. create controller/service/Repository package and start writing the code.
-src/main/java(source folder) ---com.package.service(package) ---ServiceClass(Class) ---com.package.controller(package) ---ControllerClass(Class)