如何将通过spring-boot下拉菜单获取的数据保存到数据库中？

<select id="myDropdown">
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
  <option value="option3">Option 3</option>
</select>

var dropdown = document.getElementById("myDropdown");
var selectedValue = dropdown.options[dropdown.selectedIndex].value;

@Entity
@Table(name = "my_table")
public class MyEntity {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;

  private String selectedValue;

  // getters and setters
}

public interface MyEntityRepository extends JpaRepository<MyEntity, Long> {
}

@Service
public class MyService {
  private final MyEntityRepository myEntityRepository;

  public MyService(MyEntityRepository myEntityRepository) {
    this.myEntityRepository = myEntityRepository;
  }

  public void saveSelectedValue(String selectedValue) {
    MyEntity entity = new MyEntity();
    entity.setSelectedValue(selectedValue);
    myEntityRepository.save(entity);
  }
}

@RestController
public class MyController {
  private final MyService myService;

  public MyController(MyService myService) {
    this.myService = myService;
  }

  @PostMapping("/save")
  public void saveSelectedValue(@RequestParam("selectedValue") String selectedValue) {
    myService.saveSelectedValue(selectedValue);
  }
}