Spring MVC - Flash Attribute Examples

@Controller
public class MyController {

    @RequestMapping(value = "test/{id}")
    public String handleTestRequest (@PathVariable("id") String id, Model model,
                                     RedirectAttributes ra) {
        if (!id.matches("\\d+")) {
            model.addAttribute("msg", "id should only have digits");
            return "error-page";
        } else {
            ra.addAttribute("attr", "attrVal");
            ra.addFlashAttribute("flashAttr", "flashAttrVal");
            return "redirect:/test2/{id}";
        }
    }

    @RequestMapping("test2/{id}")
    public String handleRequest (@PathVariable("id") String id,
                                 @RequestParam("attr") String attr,
                                 @ModelAttribute("flashAttr") String flashAttr,
                                 Model model) {

        model.addAttribute("id", id);
        model.addAttribute("attr", attr);
        model.addAttribute("flashAttr", flashAttr+"");
        return "my-page";
    }
}

@Controller
@RequestMapping
public class UserRegistrationController {

    @Autowired
    private UserService userService;

    @RequestMapping(value = "register", method = RequestMethod.GET)
    public String handleGetRequest (Model model) {
        model.addAttribute("user", new User());
        return "user-registration";
    }

    @RequestMapping(value = "register", method = RequestMethod.POST)
    public String handlePostRequest (@Valid @ModelAttribute("user") User user,
                                     BindingResult bindingResult,
                                     RedirectAttributes ra) {

        if (bindingResult.hasErrors()) {
            return "user-registration";
        }

        userService.saveUser(user);
        ra.addFlashAttribute("user", user);
        return "redirect:/registration-success";
    }

    @RequestMapping(value = "registration-success", method = RequestMethod.GET)
    public String handleRegistrationDone(@ModelAttribute("user") User user){
        System.out.println("user....: "+user);
        return "registration-done";
    }
}