Simplest way to read JSON from a URL in Java

Using the Maven artifact org.json:json I got the following code, which I think is quite short. Not as short as possible, but still usable.

package so4308554;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.io.Reader;import java.net.URL;import java.nio.charset.Charset;import org.json.JSONException;import org.json.JSONObject;public class JsonReader {  private static String readAll(Reader rd) throws IOException {    StringBuilder sb = new StringBuilder();    int cp;    while ((cp = rd.read()) != -1) {      sb.append((char) cp);    }    return sb.toString();  }  public static JSONObject readJsonFromUrl(String url) throws IOException, JSONException {    InputStream is = new URL(url).openStream();    try {      BufferedReader rd = new BufferedReader(new InputStreamReader(is, Charset.forName("UTF-8")));      String jsonText = readAll(rd);      JSONObject json = new JSONObject(jsonText);      return json;    } finally {      is.close();    }  }  public static void main(String[] args) throws IOException, JSONException {    JSONObject json = readJsonFromUrl("https://graph.facebook.com/19292868552");    System.out.println(json.toString());    System.out.println(json.get("id"));  }}

Here are couple of alternatives versions with Jackson (since there are more than one ways you might want data as):

  ObjectMapper mapper = new ObjectMapper(); // just need one  // Got a Java class that data maps to nicely? If so:  FacebookGraph graph = mapper.readValue(url, FaceBookGraph.class);  // Or: if no class (and don't need one), just map to Map.class:  Map<String,Object> map = mapper.readValue(url, Map.class);

And specifically the usual (IMO) case where you want to deal with Java objects, can be made one liner:

FacebookGraph graph = new ObjectMapper().readValue(url, FaceBookGraph.class);

Other libs like Gson also support one-line methods; why many examples show much longer sections is odd. And even worse is that many examples use obsolete org.json library; it may have been the first thing around, but there are half a dozen better alternatives so there is very little reason to use it.

The easiest way: Use gson, google's own goto json library. https://code.google.com/p/google-gson/

Here is a sample. I'm going to this free geolocator website and parsing the json and displaying my zipcode. (just put this stuff in a main method to test it out)

    String sURL = "http://freegeoip.net/json/"; //just a string    // Connect to the URL using java's native library    URL url = new URL(sURL);    URLConnection request = url.openConnection();    request.connect();    // Convert to a JSON object to print data    JsonParser jp = new JsonParser(); //from gson    JsonElement root = jp.parse(new InputStreamReader((InputStream) request.getContent())); //Convert the input stream to a json element    JsonObject rootobj = root.getAsJsonObject(); //May be an array, may be an object.     String zipcode = rootobj.get("zip_code").getAsString(); //just grab the zipcode