将JSONObject转换为字符串，并长返回null

Question

When jsonobject is converted to String or long it returns null . Why?

My JSON file:

{
    "memberships": [
        {
            "project": {
                "id": 30483134480107,
                "name": "Asana Integrations"
            },
            "section": null
        }
    ]
}

---

And my code:

package jsontest;

import java.beans.Statement;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.Iterator;
import java.util.Scanner;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;

public class MoreComplexJson {
    private static final String filePath = "C:\\jsonTestFile.json";

    public static void main(String[] args) {
        try {
            FileReader reader = new FileReader(filePath);
            JSONParser jsonParser = new JSONParser();
            JSONObject jsonObject = (JSONObject) jsonParser.parse(reader);

            JSONArray memberships = (JSONArray) jsonObject.get("memberships");

            for (int z = 0; z < memberships.size(); z++) {
                Iterator m = memberships.iterator();

                // take each value from the json array separately
                while (m.hasNext()) {
                    JSONObject innerObj = (JSONObject) m.next();
                    Long id = (Long) innerObj.get("id");
                    String name = (String) innerObj.get("name");
                    System.out.println("id " + id + " with name " + name);
                }
            }
        }
        catch (FileNotFoundException ex) {

            ex.printStackTrace();
            System.out.println(ex + "");
        }
        catch (IOException ex) {
            ex.printStackTrace();
            ex.printStackTrace();
            System.out.println(ex + "");
        }
        catch (ParseException ex) {
            ex.printStackTrace();
            ex.printStackTrace();
            System.out.println(ex + "");
        }
        catch (NullPointerException ex) {
            ex.printStackTrace();
            ex.printStackTrace();
            System.out.println(ex + "");
        }
    }
}

---

The output:

id null with name null

Answer 1

id and name belongs to the project JSONObject so get those two values using the project JSONObject

Try this for loop

for (int z = 0; z < memberships.size(); z++) {
    JSONObject m = (JSONObject) memberships.get(z);
    JSONObject innerObj = (JSONObject) m.get("project");

    // If you want section
    String section = (String) m.get("section");
    System.out.println("section " + section);


    Long id = (Long) innerObj.get("id");
    String name = (String) innerObj.get("name");
    System.out.println("id " + id + " with name " + name);

}

Answer 2

The problem is that when you are trying to get id and name you're not taking it from project but from object that contains project . There should be:

  JSONObject innerObj = (JsonObject) ((JSONObject) m.next()).get("project)";

Answer 3

This kind of code can get pretty ugly pretty fast. Instead you could use a higher order parser, such as Jackson . Then your code can be much cleaner and you don't have to worry about digging into the conversion of each piece of JSON.