I want to change the screen transition destination according to the contents entered in the form.

<form method="post" action="/edit">
    <h1>Please input the number</h1>
    <input type="text" name="id" th:value="${id}"/>
    <input type="submit" value="Send">
    <br>
    <ath:href="@{/}">Backenter display</a>
    </form>

@RequestMapping(value="/edit/{id}", method=RequestMethod.GET)
    publicModelAndViewedit(@ModelAttributeMyDatamydata,@PathVariableintid,ModelAndViewmav){
        mav.setViewName("edit");
        mav.addObject("title", "edit mydata");
        mav.addObject("id", id);
        Optional<MyData>data=repository.findById(long)id);
        mav.addObject("formModel", data.get());
        return mav;
    }
    @RequestMapping(value="/edit/{id}", method=RequestMethod.POST)
    @Transactional(readOnly=false)
    publicModelAndView update(@ModelAttributeMyDatamydata,@PathVariableintid,ModelAndViewmav){
        mydata.setId(id);
        repository.saveAndFlash(mydata);
        return new ModelAndView("redirect:/");
    }

    @RequestMapping(value="/searchId", method=RequestMethod.GET)
    publicModelAndViewsearchId(@ModelAttribute("formModel")MyDatamydata,ModelAndViewmav){
        mav.setViewName("searchId");
        return mav;
    }

    @RequestMapping(value="/searchId", method=RequestMethod.POST)
    publicModelAndView serachId(@PathVariableintid,ModelAndViewmav){
        mav.setViewName("searchId");
        return new ModelAndView("'/edit");
    }

--
 Whitelabel Error Page
    This application has no explicit mapping for /error, so you are seeing this as a fallback.

    Wed Oct 09 19:26:41 JST 2019
    There was an unexpected error (type=Not Found, status=404).
    No message available
--