java JSONObject JSON 数组长度

JSONObject JSON array length

提问by spiderman

I am reading the below XML in java, and converting to JSONObject[org.json.JSONObject]. and appending the metadata and returning as JSON.

我正在用 java 阅读下面的 XML，并转换为JSONObject[ org.json.JSONObject]。并附加元数据并作为 JSON 返回。

Problem: JSONObject jsonObj = service.getMyData();// custom methods and invocation

问题: JSONObject jsonObj = service.getMyData();// 自定义方法和调用

int count = jsonObj.length();// length is 1

int count = jsonObj.length();// 长度为 1

How do I take the correct count from this jsonObj? . The correct count I am referring to is 2 in this case. [2 books]

我如何从这个 jsonObj 中获取正确的计数？. 在这种情况下，我所指的正确计数是 2。[2本书]

What I tried?

我尝试了什么？

(1) System.out.println(jsonObj.length());// prints 1

(1) System.out.println(jsonObj.length());// 打印 1

API says: length() Get the number of keys stored in the JSONObject.

API 说：length() 获取存储在 JSONObject 中的键的数量。

(2) Since number of keys is returned as 1, there is no point on trying the below one, still I tried and got the error of org.json.JSONException: JSONObject["User"] not found.

(2) 由于键数返回为 1，因此尝试下面的一个没有意义，但我仍然尝试并得到了错误 org.json.JSONException: JSONObject["User"] not found.

 System.out.println(jsonObj.getJSONArray("User").length());

(3) IF I try 'Users' ie: jsonObj.getJSONArray("Users").length(), it says JSONObject["Users"] is not a JSONArray.

(3) 如果我尝试 'Users' ie: jsonObj.getJSONArray("Users").length()，它会说JSONObject["Users"] is not a JSONArray.

(4)

(4)

JSONObject jsonObj = service.getMyData();
 JSONObject jUsers =  jsonObj.getJSONObject("Users");
 JSONObject jUser =  jUsers.getJSONObject("User");
 System.out.println(jUser.length());

Error: org.json.JSONException: JSONObject["User"] is not a JSONObject.

错误： org.json.JSONException: JSONObject["User"] is not a JSONObject.

---

---

XML:

XML：

<Users>
    <User>
        <Name>Unni</Name>
        <Books>
            <Book>book1</Book>
            <Book>book2</Book>
            <Book>book3</Book>
        </Books>
    </User>
    <User>
        <Name>Ammu</Name>
        <Books>
            <Book>book1</Book>
            <Book>book2</Book>
            <Book>book4</Book>
        </Books>
    </User>
</Users>

JSON:

JSON：

{
    "Users": {
        "User": [
            {
                "Name": "Unni",
                "Books": {
                    "Book": [
                        "book1",
                        "book2",
                        "book3"
                    ]
                }
            },
            {
                "Name": "Ammu",
                "Books": {
                    "Book": [
                        "book1",
                        "book2",
                        "book4"
                    ]
                }
            }
        ]
    }
}

采纳答案by Wundwin Born

In JSONformat,

在JSON格式上，

[]is JSONArray

[]是 JSONArray

{}is JSONObject

{}是 JSONObject

In your post,

在你的帖子里，

• Users- JSONObject
• User- JSONArray
• Books- JSONObject
• Book- JSONArray

• 用户- JSONObject
• 用户- JSONArray
• 书籍- JSONObject
• 书- JSONArray

---

---

Error: org.json.JSONException: JSONObject["User"] is not a JSONObject.

As mentioned above, try with getJSONArray()

如上所述，尝试使用 getJSONArray()

 JSONArray userArray = jUsers.getJSONArray("User");

回答by spiderman

I had to call the getJSONArraymethod when retrieving the array.

我getJSONArray在检索数组时必须调用该方法。

JSONObject jsonObj = service.getMyData();
JSONObject jUsers =  jsonObj.getJSONObject("Users");
System.out.println(jUsers.getJSONArray("User").length());