用Java解析JSON数组

Question

我目前正在将JSON文件解析到Java程序中，遇到了问题。 我得到一个JSON数组，例如：

[
  {
    "itemType": "magazineArticle",
    "creators": [
      {
        "firstName": "J. Antonio",
        "lastName": "Garcia-Macias",
        "creatorType": "author"
      },
      {
        "firstName": "Jorge",
        "lastName": "Alvarez-Lozano",
        "creatorType": "author"
      },
      {
        "firstName": "Paul",
        "lastName": "Estrada-Martinez",
        "creatorType": "author"
      },
      {
        "firstName": "Edgardo",
        "lastName": "Aviles-Lopez",
        "creatorType": "author"
      }
    ],
    "notes": [],
    "tags": [],
    "title": "Browsing the Internet of Things with Sentient Visors",
    "publicationTitle": "Computer",
    "volume": "44",
    "issue": "5",
    "ISSN": "0018-9162",
    "date": "2011",
    "pages": "46-52",
    "abstractNote": "Unlike the traditional Internet, the emerging Internet of Things constitutes a mix of virtual and physical entities. A proposed IoT browser enables the exploration of augmented spaces by identifying smart objects, discovering any services they might provide, and interacting with them.",
    "extra": "CICESE Research Center, Mexico; CICESE Research Center, Mexico; CICESE Research Center, Mexico; CICESE Research Center, Mexico",
    "libraryCatalog": "IEEE Computer Society"
  }
]

问题是我每次解析时都必须检查一下是否名为“ extra”的字段在数组中，因为每次解析时都不会包含该字段。 因此，我该如何检查字段“ extra”是否存在？

Answer 1

如果没有框架，则可以使用org.json.* JSONObject和JSONArray 。 这是一个示例（未经测试）。 它将允许您检查是否存在extra密钥

String jsonAsString = "/*Your json as a String*/";
JsonArray jsonArray = new JSONArray(jsonAsString);

for(int i=0; i<jsonArray.length(); i++) {
    JSONObject jsonObject = jsonArray.getJSONObject(i);
    //Get values from your jsonObject
    jsonObject.has("extra"); //Check if extra is present
}

Answer 2

像这样使用JSONObject的“ has”方法：

Array.getJSONObject(j).has("extra")