➊

    @GetMapping
    public String requestCartId(HttpServletRequest request) {
        String sessionid = request.getSession(true).getId();
        return "redirect:/cart/" + sessionid;
    }

➋

    @PostMapping
    public @ResponseBody Cart create(@RequestBody Cart cart) {
        return cartService.create(cart);
    }

➌

    @GetMapping("/{cartId}")
    public String requestCartList(@PathVariable(value="cartId") String cartId, Model model) {
        Cart cart = cartService.read(cartId);
        model.addAttribute("cart", cart);
        return "cart";
    }

➍

    @PutMapping("/{cartId}")
    public @ResponseBody Cart read(@PathVariable(value="cartId") String cartId) {
        return cartService.read(cartId);
    }

}