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I'm new to JSON and REST. I'm working with a server that returns strings like these:

[{"username":"Hello","email":"[email protected]","credits":"100","twitter_username":""},{"username":"Goodbye","email":"[email protected]","credits":"0","twitter_username":""}]

I've managed to print them out as strings on the console, but now I want to convert them into a JSON array. The code I have so far returns no errors, but I don't know what to put into the constructor for the new JSON array. I've been referring to a piece of code sent to me by a colleague, in which the constructor was new JSONArray(response) but he never told me what 'response' was.

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

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

import sun.misc.BASE64Encoder;

public class NetClientGet {

    public static void main(String[] args) {

      try {

        URL url = new URL("http://username:[email protected]/index.php/api/users/get_users/");
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("GET");

        BASE64Encoder enc = new sun.misc.BASE64Encoder();
        String userpassword = "username:password";
        String encoded = enc.encode(userpassword.getBytes());
        conn.setRequestProperty("Authorization", "Basic " + encoded);

        if (conn.getResponseCode() != 200) {
            throw new RuntimeException("Failed : HTTP error code : "
                    + conn.getResponseCode());
        }

        BufferedReader br = new BufferedReader(new InputStreamReader(
            (conn.getInputStream())));

        String output;
        System.out.println("Output from Server .... \n");
        while ((output = br.readLine()) != null) {
            System.out.println(output);
        }

        JSONArray array = new JSONArray(output);

        for (int i =0; i < array.size(); i++) {
            JSONObject row = array.getJSONObject(i);
            String user = row.getString("username");
            System.out.println(user);
        }

        conn.disconnect();

      } catch (MalformedURLException e) {

        e.printStackTrace();

      } catch (IOException e) {

        e.printStackTrace();

      }

    }
}
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3 Answers

up vote 4 down vote accepted
  • use GSON to format the string as JsonArray
  • then traverse the JsonArray to get the values

the code sample

String json = "[{\"username\":\"Hello\",\"email\":\"[email protected]\",\"credits\":\"100\",\"twitter_username\":\"\"},{\"username\":\"Goodbye\",\"email\":\"[email protected]\",\"credits\":\"0\",\"twitter_username\":\"\"}]";
JsonArray jArray = new JsonParser().parse(json).getAsJsonArray();
for (int i=0;i<jArray.size();i++) {
    JsonObject jsonObject = jArray.get(i).getAsJsonObject();
    System.out.println(jsonObject.get("username"));
    System.out.println(jsonObject.get("email"));
    System.out.println(jsonObject.get("credits"));
    System.out.println(jsonObject.get("twitter_username"));
    System.out.println("*********");
}
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Thank you! Works like a charm – Tiffany Jul 16 '12 at 13:49
I do have one question though - is there a way to get the json string without having to hard code it like that? – Tiffany Jul 16 '12 at 13:55
1  
try the getJson function in the code sample that i gave as an answer, in the following post : stackoverflow.com/questions/11471884/…. Using that, you can download json data from external servers – sunil Jul 16 '12 at 16:21
up vote 1 down vote

I am using gson library to manipulate json. You can download gson from here. It is a very good library to handle json. Create json parser first, it will parse the json string:

JsonParser parser = new JsonParser();

now initialize an empty json array

JsonArray jArray = new JsonArray();

Now use the parser to create json array

jArray = parser.parse(outputString).getAsJsonArray();
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up vote 0 down vote

I have used org.json.simple.JSONObject and org.json.simple.JSONArray, and I hope net.sf.json.JSONArray also work same.

You should put following string format for output (JSONArray array = new JSONArray(output); )

 {"YOUR_ARRAY_NAME": [{"username":"Hello","email":"[email protected]","credits":"100","twitter_username":""},{"username":"Goodbye","email":"[email protected]","credits":"0","twitter_username":""}]}

Now this is String representation of JSONArray.

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