@GetMapping("/demo1")
    public ModelAndView demo1(){
        String url = "redirect:https://www.cctv.com";
        return new ModelAndView(url);
    }

 @GetMapping("/demo2")
    public String demo2(){
        return "redirect:https://www.baidu.com";
    }

  @GetMapping("/demo3")
   public void demo3(HttpServletResponse response){
        response.setStatus(302);
        response.setHeader("location","https://www.bilibili.com");
   }