可选的长参数'id'存在但不能转换为空值

Question

I have two methods in my Spring controller:

    @RequestMapping(method = RequestMethod.GET, value = CARD_PATH)
    public @ResponseBody List<BaseballCard> getAllCards()

    @RequestMapping(method = RequestMethod.GET, value = CARD_PATH + "/{id}")
    public BaseballCard getCard(@PathVariable("id") long id)

I get the following error when issuing a HTTP request for GET /bbct/api/v1.0/card/1 .

Optional long parameter 'id' is present but cannot be translated into a null value due to being declared as a primitive type.

The suggestion is to declare id as a Long ; however, I'd prefer to not do this.

I wonder why Spring thinks the id parameter is optional? Since I have a another method which processes requests when the id is missing, the id was certainly supplied, if the request is dispatched to getCard() .

Here is the full controller:

@Controller
public class BaseballCardController {

    private static final String CARD_PATH = "/bbct/api/v1.0/card";

    private List<BaseballCard> cards = new ArrayList<BaseballCard>();

    @RequestMapping(method = RequestMethod.POST, value = CARD_PATH)
    public @ResponseBody
    BaseballCard addCard(@RequestBody BaseballCard card) {
        cards.add(card);
        card.setId(cards.size());
        return card;
    }

    @RequestMapping(method = RequestMethod.GET, value = CARD_PATH)
    public @ResponseBody List<BaseballCard> getAllCards() {
        return cards;
    }

    @RequestMapping(method = RequestMethod.GET, value = CARD_PATH + "/{id}")
    public BaseballCard getCard(@PathVariable("id") long id) {
        return cards.get((int)(id - 1));
    }

}

Answer 1

I think what happened was you (inadvertently?) made request to /bbct/api/v1.0/card/ (pay attention to the trailing slash at the end) and it gets mapped into getCard() instead of getAllCards()

Probably it's a good idea to map the id into Long and set the required = false attribute on @PathVariable("id") , then do a redirect into getAllCards() . This way you can map both slash-suffixed and non-slash-suffixed version of getAllCards()