Валидация в Rest контроллере

@Entity
@Table(name = "classes")
public class Group {

        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private Long id;

        @NotNull
        @Pattern(regexp = "^[1]?\\d{1}[А-Я]{1}$")
        private String name;

        @NotNull
        @OneToOne
        @JoinColumn(name = "teacher_id")
        User teacher;

        @OneToMany(fetch = FetchType.EAGER)
        @JoinTable (
                name="class_students",
                joinColumns={ @JoinColumn(name="class_id", referencedColumnName="id") },
                inverseJoinColumns={@JoinColumn(name="student_id", referencedColumnName="id")}
            )
        private List<User> users;

        public String getName() {
                return name;
        }

        public void setName(String name) {
                this.name = name;
        }

        public User getTeacher() {
                return teacher;
        }

        public void setTeacher(User teacher) {
                this.teacher = teacher;
        }

        public List<User> getUsers() {
                return users;
        }

        public void setUsers(List<User> users) {
                this.users = users;
        }

        public Long getId() {
                return id;
        }
        
        

}

@RestController
@RequestMapping(value = "/classes", produces = "application/json")
public class GroupRestController{
        
        @Autowired
        GroupService groupService;
        
        @GetMapping
        @ResponseBody
        public List<Group> list() {
                return groupService.list();
        }
        
        @PostMapping
        public ResponseEntity<Object> createGroup(@Valid @RequestBody Group group) {
                groupService.save(group);
                return new ResponseEntity<>("Class is created successfully", HttpStatus.CREATED);
        }
                 
}