使用jsonpath仅提取根节点

Question

简而言之，我试图使用带有java的jsonpath从JSON数据中仅提取根节点。在下面的JSON数据中，根级别只有2个节点store和expensive。我的目标是获取存储在变量中的那两个节点的名称，然后继续创建一个断言，表示节点不为空或为空。

{
  "store": {
    "book": [
      {
        "category": "reference",
        "author": "Nigel Rees",
        "title": "Sayings of the Century",
        "price": 8.95
      },
      {
        "category": "fiction",
        "author": "Evelyn Waugh",
        "title": "Sword of Honour",
        "price": 12.99
      },
      {
        "category": "fiction",
        "author": "Herman Melville",
        "title": "Moby Dick",
        "isbn": "0-553-21311-3",
        "price": 8.99
      },
      {
        "category": "fiction",
        "author": "J. R. R. Tolkien",
        "title": "The Lord of the Rings",
        "isbn": "0-395-19395-8",
        "price": 22.99
      }
    ],
    "bicycle": {
      "color": "red",
      "price": 19.95
    }
  },
  "expensive": 10

这就是我的尝试：

JsonPath jpath = new JsonPath(json);
Map<String, Object> loc = jpath.get("$");

$告诉我所有的根节点和孩子们。有没有办法排除孩子并获得根节点？