what is the best way to design the skeleton of springboot application

I am writing a springboot application that should calculate the grade of a student. You should read the name of the student from command line, and call an API that will return the student ID in JSON. Then I will take the Student ID and call another API that would return the total of the student Marks in JSON. Then I should calculate the grade accordingly. The calculation is as follow: F=<60, D=<65, C=< 75, B=<85, A=<100. Below is my hypothetical view of how I will write the project, I think I know how to write the code that will function, but I am stuck with what is the best skeleton for the project or design of classes. Below is how I think it should be written.

@Controller
// Rest call to the Student API
public class StudentController {
    private static final Logger log = LoggerFactory.getLogger(ClientController.class);
    private RestOperations rest;
    private Config config;  //to read the URL
    .....

    @Controller
// Rest call to the grades API
public class GradsController 
{
    private static final Logger log = LoggerFactory.getLogger(ClientController.class);
    private RestOperations rest;
    private Config config; //to read the URL
    .....

Configuration
@ConfigurationProperties(prefix="api.call")
public class Config {
    private String URL;
    .....

   public class Student {
    @JsonProperty("Data")
    private Elements[] elements;
    .......

 public class Grads {
        @JsonProperty("Subjects")
        private String[] subjects;
        .......

@Service
public class CalculateGrade {
    private String marks;
    private HashMap <String, Integer> gradeMap;

    CalculateGrade( String marks)
    {
        this.marks = marks;
        this.carName = carName;
        fillMap();
    }
    private void fillMap()
    {
        gradeMap= new HashMap<>();
        gradeMap.put("A",100);
        gradeMap.put("B", 85 );
       ..........
     }
     public String getGrade()
    {
      // do calculations;
    }

    @SpringBootApplication 
    @ConfigurationPropertiesScan ("Config") 
    public class MyApplication {

    private static final Logger log = LoggerFactory.getLogger(MyApplication.class);     
    @Autowired  StudentController StudentController;

    public static void main(String[] args) {        
         SpringApplication.run(MyApplication.class, args);

    }