I am studying Spring and currently, I am using Validation,

I face 2 problems:

1. Not add @Valid to my @PostMapping for Student entity => Validation still executed
2. Practicing to store date with timezone:

• borrow_date @CreationTimestamp => database store random UTC @@, not local UTC as expected
• return_date: input “returnDate”: “2026-01-01T00:00:00+07:00” => database: 2025-12-31 17:00:00.000000 Not same as input

Student Entity class

@Data
@Entity
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    @NotBlank
    private String name;
    @Min(value = 18)
    private int age;
    @NotBlank
    private String address;
    @Pattern(regexp = "^0+[0-9]{9}$")
    private String phone;
    @CreationTimestamp //default timestamp
    private Instant borrowDate; //Offetdatetime use for UTC, Zonedatetime use Europe/Paris meaning adhead or behind Europe how many hours
    @Future
    private Instant returnDate;
    @NotNull
    private String timeZone = "UTC+7:00";
    @OneToMany(mappedBy = "student", cascade = CascadeType.MERGE)
    private List<Book> list = new ArrayList<>();
}

Student service

public interface StudentService {
void addStudent(Student student);

    Student findStudentById(int id);
    
    void updateStudent(Student student);
    
    List<Book> getListBook(int id);

}

@Service
class StudentServiceImp1 implements StudentService {
private final StudentRepo studentRepo;
@Autowired
public StudentServiceImp1(StudentRepo studentRepo) {
this.studentRepo = studentRepo;
}
@Override
@Transactional
public void addStudent(Student student) {
studentRepo.save(student);
}

Student Controller

@RestController
@RequestMapping("/student")
public class StudentController {
    private final StudentService studentService;

    @Autowired
    public StudentController(StudentService studentService) {
        this.studentService = studentService;
    }

    @PostMapping("/add")
    private Student addStudent(@RequestBody Student student){
        studentService.addStudent(student);
        System.out.println("Student controller: Show student id when adding student "+student.getId());
        return student;
    }