Controller.java

@GetMapping("/add")
public String showAddPersonForm(Person person) { 
  return "add-person"; 
}

@PostMapping("/add") 
public String addPerson(@Valid Person person, BindingResult result, Model model) { 
  if (result.hasErrors()) { 
    return "add-person"; 
  }
  repository.save(person); 
  return "redirect:/index"; 
}