详解 SpringMVC 中获取请求参数

@Controller
@RequestMapping("/users")
public class UserController {

    // 使用@RequestParam获取查询参数
    @GetMapping
    public String getUsers(@RequestParam(name = "id", required = false) Integer id, Model model) {
        // 如果存在id参数，则根据id查询用户
        if (id != null) {
            // 假设有findUserById的方法
            User user = userService.findUserById(id);
            model.addAttribute("user", user);
        }
        // 不存在id参数，则查询所有用户
        List<User> users = userService.findAllUsers();
        model.addAttribute("users", users);
        return "users";
    }

    // 使用@PathVariable获取URL中的路径变量
    @GetMapping("/{userId}")
    public String getUser(@PathVariable("userId") Integer userId, Model model) {
        User user = userService.findUserById(userId);
        model.addAttribute("user", user);
        return "user";
    }

    // 使用@RequestBody获取请求体中的JSON数据
    @PostMapping
    public ResponseEntity<?> createUser(@RequestBody User user) {
        User createdUser = userService.createUser(user);
        return ResponseEntity.status(HttpStatus.CREATED).body(createdUser);
    }

    // 使用HttpServletRequest获取请求数据
    @GetMapping("/current")
    public void currentUser(HttpServletRequest request, HttpServletResponse response) {
        // 获取请求参数
        String queryParam = request.getParameter("param");
        // 获取请求头
        String authHeader = request.getHeader("Authorization");
        // 获取Cookie
        Cookie[] cookies = request.getCookies();
        if (cookies != null) {
            for (Cookie cookie : cookies) {
                if ("sessionId".equals(cookie.getName())) {
                    String sessionId = cookie.getValue();
                    // ...
                }
            }
        }
    }

    // 使用@ModelAttribute绑定表单数据到Java对象
    @PostMapping("/register")
    public String registerUser(@ModelAttribute UserForm userForm, BindingResult bindingResult, Model model) {
        if (bindingResult.h