org.json.JSONException: JSONObject["userId"] 未找到。 .JSONException [关闭]

Question

现在我的问题是 json 对象找不到我不知道为什么的密钥。但是正如您在错误中看到的那样，响应已打印出所有键。

package com.ar.team.company.project;

import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class Main {

    public static void main(String[] args) {
        try {
            Main.readJsonData();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void readJsonData() throws Exception {
        // Initializing:
        String url = "https://jsonplaceholder.typicode.com/posts/1"; // Our url.
        URL obj = new URL(url); // Our url object(To open connection from it.).
        HttpURLConnection con = (HttpURLConnection) obj.openConnection(); // Our 
        httpURLConnection to connect to json.
        // Optional default is GET for getting the data:
        con.setRequestMethod("GET");
        // Add request header:
        con.setRequestProperty("User-Agent", "Mozilla/5.0");
        // Getting the response code:
        int responseCode = con.getResponseCode();
        // Show to user the data:
        System.out.println("Sending 'GET' request to URL: " + url);
        System.out.println("Response code: " + responseCode);
        // Start read the data:
        BufferedReader in = new BufferedReader(new                         
        InputStreamReader(con.getInputStream())); // Our buffered reader.
        String inputLine; // For checking the new line.
        StringBuilder response = new StringBuilder(); // Here is our reading data.
        while ((inputLine = in.readLine()) != null) {
            response.append(inputLine); // Append the data for response(StringBuilder).
        }
        in.close(); // Closing the buffered reader.
        // Print in String:
        System.out.println("The response data: " + response);
        // Read JSON response and print:
        JSONObject myResponse = new JSONObject(response);
        System.out.println("Result After Reading JSON Response:".toUpperCase());
        // All Result:
        System.out.println("UserId: " + myResponse.getString("userId"));
        System.out.println("Id: " + myResponse.getString("id"));
        System.out.println("Title: " + myResponse.getString("title"));
        System.out.println("Body: " + myResponse.getString("body"));
    }

}

错误

Sending 'GET' request to URL: https://jsonplaceholder.typicode.com/posts/1
Response code: 200
The response data: {  "userId": 1,  "id": 1,  "title": "sunt aut facere repellat 
provident occaecati excepturi optio reprehenderit",  "body": "quia et suscipit\nsuscipit 
recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas 
totam\nnostrum rerum est autem sunt rem eveniet architecto"}
RESULT AFTER READING JSON RESPONSE:
org.json.JSONException: JSONObject["userId"] not found.
   at org.json.JSONObject.get(JSONObject.java:516)
   at com.ar.team.company.project.Main.readJsonData(Main.java:48)
   at com.ar.team.company.project.Main.main(Main.java:14)

Answer 1

代码错误：

1. 错误：JSONException: JSONObject["userId"] not found.

   response 是一个StringBuilder，所以new JSONObject(response) 正在调用JSONObject(Object bean) 构造函数。由于StringBuilder 不是Java Bean，它没有属性，JSONObject 为空。

   将代码更改为new JSONObject(response.toString())，以便调用JSONObject(String source) 构造函数。

2. 错误：JSONException: JSONObject["userId"] not a string.

   userId 的值是一个 JSON 数字，因此您必须调用其中一种 get 方法来检索数值，例如getInt(String key)，或任何其他人：getLong、getBigInteger、getDouble、getFloat、getNumber。

   将代码更改为getInt("userId")。

3. 错误：JSONException: JSONObject["id"] not a string.

   同 #2：将代码更改为 getInt("id")。