Question

下面我附上了Java代码，首先我要检索＆＃34;图像＆＃34;结果为＆＃34; {＆＃34; jpg＆＃34;：＆＃34; JPEG文件＆＃34;，＆＃34; gif＆＃34;：＆＃34; GIF文件＆＃34;，＆＃ 34; png＆＃34;：＆＃34; PNG文件＆＃34;} ＆＃34;

使用结果，试图获得＆＃34; jpg＆＃34;节点，无法检索数据，而是我收到错误java.lang.String cannot be cast to org.json.simple.JSONObject

我喜欢拍摄照片，然后是jpg。不直接JPG值

import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;

    public class JSONDemo {

        public static void main(String[] args) {
            try{
            String jsonfile="{ \"name\" : \"Raj\", \"Address\" : \"Chennai\", \"images\": { \"jpg\" : \"JPEG file\", \"png\" : \"PNG File\", \"gif\" : \"GIF file\" }}";
            JSONObject jobject=new JSONObject();
            JSONParser jparser=new JSONParser();
            jobject = (JSONObject) jparser.parse(jsonfile);
            jobject=(JSONObject) jobject.get("images");
            System.out.println(jobject);
            System.out.println(jobject.getClass().getName());

            jobject=(JSONObject) jobject.get("jpg");
            }catch(Exception e){
                System.out.println(e.getMessage());
            }
        }
    }

Answer 1

这里的错误是“jpg”不是JSONObject，而是具有关联值"JPEG file"的密钥，它是一个简单的字符串。这就是你得到这样的错误的原因。

在ordre中检索与键jpg关联的值，请阅读以下代码。我添加了一些注释来帮助您理解每个步骤，但请随时询问更多详细信息。

    String jsonfile="{ \"name\" : \"Raj\", \"Address\" : \"Chennai\", \"images\": { \"jpg\" : \"JPEG file\", \"png\" : \"PNG File\", \"gif\" : \"GIF file\" }}";

    JSONObject jobject = new JSONObject();
    JSONParser jparser = new JSONParser();

    //Convert your string jsonfile into a JSONObject   
    try {
        jobject = (JSONObject) jparser.parse(jsonfile);
    } catch (ParseException ex) {
        Logger.getLogger(Josimarleewords.class.getName()).log(Level.SEVERE, null, ex);
    }

    System.out.println(jobject.toString());    
    //{"Address":"Chennai","name":"Raj","images":{"jpg":"JPEG file","png":"PNG File","gif":"GIF file"}}

    //Get the node image, and convert it into a JSONObject
    //You're able to do so, because the value associated to "images"
    //is in json format.
    jobject=(JSONObject) jobject.get("images");
    System.out.println(jobject.toString()); 
    //{"jpg":"JPEG file","png":"PNG File","gif":"GIF file"}

    //Retrieves the value associated to the key jpg.
    //The value here is not in json format, it is a simple string
    String jpg = (String)jobject.get("jpg");                 
    System.out.println(jpg.toString());
    //JPEG file

检索JSON对象

1 个答案: