简述Spring MVC中@PathVariable注释的作用 ？

@GetMapping("/user/{userId}")
public String getUserById(@PathVariable("userId") int userId) {
    return "userDetails";  // 返回对应userId的用户信息
}

@GetMapping("/user/{userId}")
public String getUserById(@PathVariable("userId") int userId) {
    return "userDetails";  // 根据userId查找用户信息
}

@GetMapping("/post/{postId}/comment/{commentId}")
public String getComment(@PathVariable("postId") int postId, @PathVariable("commentId") int commentId) {
    return "postCommentDetails";  // 返回特定postId和commentId的评论信息
}

@GetMapping("/user/{userId}/details")
public String getUserDetails(@PathVariable("userId") String userId,
                              @RequestParam(defaultValue = "basic") String type) {
    // 使用defaultValue提供默认值
    return "userDetails";
}

@GetMapping("/user/{userId}/post/{postId}")
public String getUserPost(@PathVariable("userId") int userId, 
                          @PathVariable("postId") int postId) {
    return "userPostDetails";
}

@GetMapping("/user/{userId}")
public String getUserById(@PathVariable int userId) {  // 直接使用相同名称
    return "userDetails";
}

@GetMapping("/user/{userId}")
public String getUserById(@PathVariable("userId") int id) {  // 显式指定名称
    return "userDetails";
}