@pathvariable이 발견되지 않으면 null 수 있습니다.

Question

경로 변수가 URL에 있지 않으면 @PathVariable가 null를 반환 할 수 있습니까?그렇지 않으면 두 개의 핸들러를 만들어야합니다./simple 및 /simple/{game}에 대해 다른 하나는 둘 다 정의되지만 둘 다 동일하게 수행합니다. 그러나 목록에서 첫 번째를 선택하지만 게임 파라미터가 정의 된 경우 i를 사용합니다.

@RequestMapping(value = {"/simple", "/simple/{game}"}, method = RequestMethod.GET)
public ModelAndView gameHandler(@PathVariable("example") String example,
            HttpServletRequest request) {

.

페이지를 열려고 할 때 얻을 수있는 것입니다.

로 인해 java.lang.IllegalStateException : @RequestMapping의 @PathVariable [예제]를 찾을 수 없습니다

Answer 1

They cannot be optional, no. If you need that, you need two methods to handle them.

This reflects the nature of path variables - it doesn't really make sense for them to be null. REST-style URLs always need the full URL path. If you have an optional component, consider making it a request parameter instead (i.e. using @RequestParam). This is much better suited to optional arguments.

Answer 2

As others have already mentioned No you cannot expect them to be null when you have explicitly mentioned the path parameters. However you can do something like below as a workaround -

@RequestMapping(value = {"/simple", "/simple/{game}"}, method = RequestMethod.GET)
public ModelAndView gameHandler(@PathVariable Map<String, String> pathVariablesMap,
            HttpServletRequest request) {
    if (pathVariablesMap.containsKey("game")) {
        //corresponds to path "/simple/{game}"
    } else {
        //corresponds to path "/simple"
    }           
}

If you are using Spring 4.1 and Java 8 you can use java.util.Optional which is supported in @RequestParam, @PathVariable, @RequestHeader and @MatrixVariable in Spring MVC

@RequestMapping(value = {"/simple", "/simple/{game}"}, method = RequestMethod.GET)
public ModelAndView gameHandler(@PathVariable Optional<String> game,
            HttpServletRequest request) {
    if (game.isPresent()) {
        //game.get()
        //corresponds to path "/simple/{game}"
    } else {
        //corresponds to path "/simple"
    }           
}

Answer 3

You could always just do this:

@RequestMapping(value = "/simple", method = RequestMethod.GET)
public ModelAndView gameHandler(HttpServletRequest request) {
    gameHandler2(null, request)
}

@RequestMapping(value = "/simple/{game}", method = RequestMethod.GET)
public ModelAndView gameHandler2(@PathVariable("game") String game,
        HttpServletRequest request) {

Answer 4

@RequestMapping(value = {"/simple", "/simple/{game}"}, method = RequestMethod.GET)
public ModelAndView gameHandler(@PathVariable(value="example",required = false) final String example)

Try this approach, it worked for me.