Gson deserializes JSON property as null for static field

Question

I am trying to get hdurl from this json:

{
  "date": "2022-12-08",
  "explanation": "A camera on board the uncrewed Orion spacecraft captured this view on December 5 as Orion approached its return powered flyby of the Moon.  Below one of Orion's extended solar arrays lies dark, smooth, terrain along the western edge of the Oceanus Procellarum. Prominent on the lunar nearside Oceanus Procellarum, the Ocean of Storms, is the largest of the Moon's lava-flooded maria. The lunar terminator, shadow line between lunar night and day, runs along the left of the frame. The 41 kilometer diameter crater Marius is top center, with ray crater Kepler peeking in at the edge, just right of the solar array wing. Kepler's bright rays extend to the north and west, reaching the dark-floored Marius. Of course the Orion spacecraft is now headed toward a December 11 splashdown in planet Earth's water-flooded Pacific Ocean.",
  "hdurl": "https://apod.nasa.gov/apod/image/2212/art001e002132.jpg",
  "media_type": "image",
  "service_version": "v1",
  "title": "Orion and the Ocean of Storms",
  "url": "https://apod.nasa.gov/apod/image/2212/art001e002132_apod1024.jpg"
}

My code is:

package space;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLConnection;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.net.http.HttpRequest.BodyPublisher;
import java.net.http.HttpRequest.BodyPublishers;
import java.net.http.HttpResponse.BodyHandler;
import java.net.http.HttpResponse.BodyHandlers;
import java.nio.file.Paths;

import com.google.gson.Gson;

import java.net.http.HttpResponse.BodyHandlers;

public class Output {

    public static void main(String input) throws IOException, InterruptedException, URISyntaxException {
        if (input == "news") {
                HttpClient client = HttpClient.newHttpClient();
                HttpRequest getRequest;
                getRequest = HttpRequest.newBuilder()
                    .uri(new URI("https://api.nasa.gov/planetary/apod?api_key=vtBLyZ1ON5hZybof2EfuXHWgdcNAXh9DdZrZAOvK")) //Demo key, (replace later)
                    .build();
                    HttpResponse<String> response = client.send(getRequest, BodyHandlers.ofString());
            System.out.println(response.body());
            Objects ojkn = new Objects();
            Gson gson = new Gson();
            ojkn = gson.fromJson(response.body(),Objects.class);
            String result = ojkn.geturl();
            System.out.println(result);
            


        }
    }
}

And here is my Objects file:

package space;

public class Objects {
    private static String url;

    public static String geturl() {
        return url;
    }
    public void sethdurl(String url) {
        Objects.url=url;
    }
    public Object get(String string) {
        return null;
    }

}

My code is supposed to tell me the complete json, then I am wanting to get just the link, url , but what I get out is null for the link.

Answer 1

Your Objects class is not ok. url must not be static.

This is the correct version:

public class Objects {
        private  String url;

        public String getUrl() {
            return url;
        }

        public void setUrl(String url) {
            this.url = url;
        }
    }