springboot如何重定向携带数据 RedirectAttributes

public interface RedirectAttributes extends Model {
    RedirectAttributes addAttribute(String var1, @Nullable Object var2);
    RedirectAttributes addAttribute(Object var1);
    RedirectAttributes addAllAttributes(Collection<?> var1);
    RedirectAttributes mergeAttributes(Map<String, ?> var1);
    RedirectAttributes addFlashAttribute(String var1, @Nullable Object var2);
    RedirectAttributes addFlashAttribute(Object var1);
    Map<String, ?> getFlashAttributes();
}

@PostMapping("/regist")
public String register(RedirectAttributes attribdatautes){
    int data = 1;
    attributes.addFlashAttribute("data",data);
    return "redirect:http://auth.gulimail.com/reg.html";
}

@GetMapping("/addToCartSuccess.html")
    public String addToCartSuccessPagez(@RequestParam("skuId") Long skuId,Model model){
        CartItem cartItem = cartService.selectCartItemInfo(skuId);
        model.addAttribute("item",cartItem);
        return "success";
    }

@GetMapping("/redirect")
public String redirect(RedirectAttributes redirectAttributes)
{
    redirectAttributes.addFlashAttribute("test", 1);
    return "redirect:/show";
}
 
@GetMapping("/show")
@ResponseBody
//必须要添加@ModelAttribute标签，否侧将读不到值
//且必须指定变量名，并不会自动做匹配
public Map<String, Object> show(@ModelAttribute("test") int test)
{
    Map<String, Object> modelMap = new HashMap<>();
    modelMap.put("String", test);
    return modelMap;
}