Parsing JSON data using JSONReader or JSONObject / JSONArray

Question

I have JSON (shown below), I'm trying to parse all JSON, and each object will be a new instance of the class declaring the variables below. What is the best way to do this? Should I use JSONReader or use JSONObject and JSONArray. I read some lessons and asked some general questions, but I did not see examples of how to parse data like this.

{ "id": 356, "hassubcategories": true, "subcategories": [ { "id": 3808, "CategoryName": "Current Products", "CategoryImage": null, "hassubcategories": true, "subcategories": [ { "id": 4106, "CategoryName": "Architectural", "CategoryImage": "2637", "hassubcategories": true, "subcategories": [ { "id": 391, "CategoryName": "Flooring", "CategoryImage": "2745", "hassubcategories": false } ] } ] }, { "id": 3809, "CategoryName": "Non-Current Products", "CategoryImage": null, "hassubcategories": true, "subcategories": [ { "id": 4107, "CategoryName": "Desk", "CategoryImage": "2638", "hassubcategories": true, "subcategories": [ { "id": 392, "CategoryName": "Wood", "CategoryImage": "2746", "hassubcategories": false } ] } ] } ] } 

Answer 1

if I had to do this, I will parse the entire string in a JSONObject

 JSONObject obj = new JSONObject(str); 

then I see that your subcategories are JSONArray. Therefore, I will convert it this way

 JSONArray arr = new JSONArray(obj.get("subcategories")); 

with this you can loop and instantiate a class object

 for(int i = 0; i < arr.length; i++) JSONObject temp = arr.getJSONObject(i); Category c = new Category(); c.setId(temp.get("id")); 

Answer 2

You can use JSON Object / JSON Array only if the size of your json data is less than 1 MB. You should also go with JSONReader. JSONReader actually uses a streaming approach, while JSONObject and JSONArray end up loading all the data into RAM right away, which raises an OutOfMemoryException in case of a larger json.

Answer 3

GSON is the easiest way to work with nested objects.

like this:

 //after the fetched Json: Gson gson = new Gson(); Event[] events = gson.fromJson(yourJson, Event[].class); //somewhere nested in the class: static class Event{ int id; String categoryName; String categoryImage; boolean hassubcategories; ArrayList<Event> subcategories; } 

You can check out this tutorial, http://androidsmith.com/2011/07/using-gson-to-parse-json-on-android/ or http://www.javacodegeeks.com/2011/01/android-json -parsing-gson-tutorial.html or http://www.androidhive.info/2012/01/android-json-parsing-tutorial/

Answer 4

this is a simple example of using Gson to model an array of objects through JsonReader:

 protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); tv = (TextView) findViewById(R.id.textviewtest); Task task = new Task(); task.execute(); } private class Task extends AsyncTask<Void, Void, ArrayList<Flower>> { @Override protected ArrayList<Flower> doInBackground(Void... params) { ArrayList<Flower> arrayFlowers = new ArrayList<Flower>(); Flower[] f = null; try { String uri = "http://services.hanselandpetal.com/feeds/flowers.json"; URL url = new URL(uri); HttpURLConnection con = (HttpURLConnection) url.openConnection(); Gson gson = new Gson(); JsonReader reader = new JsonReader(new InputStreamReader(con.getInputStream())); f = gson.fromJson(reader, Flower[].class); for (Flower flower : f) { arrayFlowers.add(flower); } } catch (MalformedURLException e) { return null; } catch (IOException e) { return null; } return arrayFlowers; } @Override protected void onPostExecute(ArrayList<Flower> result) { StringBuilder sb = new StringBuilder(); for (Flower flower : result) { sb.append(flower.toString()); } tv.setText(sb.toString()); } } 

and object i modeled:

 public class Flower { private String category; private double price; private String instructions; private String photo; private String name; private int productId; public String getCategory() { return category; } public void setCategory(String category) { this.category = category; } public double getPrice() { return price; } public void setPrice(double price) { this.price = price; } public String getInstructions() { return instructions; } public void setInstructions(String instructions) { this.instructions = instructions; } public String getPhoto() { return photo; } public void setPhoto(String photo) { this.photo = photo; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getProductId() { return productId; } public void setProductId(int productId) { this.productId = productId; } @Override public String toString() { return getProductId() + " : " + name + "\n" + price + "$" + "\n" + "\n"; } 

Answer 5

The given JSON data does not seem to match the JSON data structure. You will need to construct the data in the same way as described in the third link posted by Mustafa. This is a really great tutorial. I followed the steps and it really works!

Answer 6

  //import java.util.ArrayList; //import org.bson.Document; Document root = Document.parse("{ \"id\" : 356, \"hassubcategories\" : true, \"subcategories\" : [{ \"id\" : 3808, \"CategoryName\" : \"Current Products\", \"CategoryImage\" : \"image.img\", \"hassubcategories\" : true, \"subcategories\" : [{ \"id\" : 4106, \"CategoryName\" : \"Architectural\", \"CategoryImage\" : \"2637\", \"hassubcategories\" : true, \"subcategories\" : [{ \"id\" : 391, \"CategoryName\" : \"Flooring\", \"CategoryImage\" : \"2745\", \"hassubcategories\" : false }] }] }, { \"id\" : 3809, \"CategoryName\" : \"Non-Current Products\", \"CategoryImage\" : \"image.img\", \"hassubcategories\" : true, \"subcategories\" : [{ \"id\" : 4107, \"CategoryName\" : \"Desk\", \"CategoryImage\" : \"2638\", \"hassubcategories\" : true, \"subcategories\" : [{ \"id\" : 392, \"CategoryName\" : \"Wood\", \"CategoryImage\" : \"2746\", \"hassubcategories\" : false }] }] }] }"); System.out.println((root.get("id"))); System.out.println((root.get("hassubcategories"))); System.out.println((((Document)((ArrayList)root.get("subcategories")).get(0)).get("id"))); System.out.println(((String)((Document)((ArrayList)root.get("subcategories")).get(0)).get("CategoryName"))); System.out.println(((String)((Document)((ArrayList)root.get("subcategories")).get(0)).get("CategoryImage"))); System.out.println((((Document)((ArrayList)root.get("subcategories")).get(0)).get("hassubcategories"))); System.out.println((((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(0)).get("subcategories")).get(0)).get("id"))); System.out.println(((String)((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(0)).get("subcategories")).get(0)).get("CategoryName"))); System.out.println(((String)((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(0)).get("subcategories")).get(0)).get("CategoryImage"))); System.out.println((((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(0)).get("subcategories")).get(0)).get("hassubcategories"))); System.out.println((((Document)((ArrayList)((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(0)).get("subcategories")).get(0)).get("subcategories")).get(0)).get("id"))); System.out.println(((String)((Document)((ArrayList)((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(0)).get("subcategories")).get(0)).get("subcategories")).get(0)).get("CategoryName"))); System.out.println(((String)((Document)((ArrayList)((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(0)).get("subcategories")).get(0)).get("subcategories")).get(0)).get("CategoryImage"))); System.out.println((((Document)((ArrayList)((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(0)).get("subcategories")).get(0)).get("subcategories")).get(0)).get("hassubcategories"))); System.out.println((((Document)((ArrayList)root.get("subcategories")).get(1)).get("id"))); System.out.println(((String)((Document)((ArrayList)root.get("subcategories")).get(1)).get("CategoryName"))); System.out.println(((String)((Document)((ArrayList)root.get("subcategories")).get(1)).get("CategoryImage"))); System.out.println((((Document)((ArrayList)root.get("subcategories")).get(1)).get("hassubcategories"))); System.out.println((((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(1)).get("subcategories")).get(0)).get("id"))); System.out.println(((String)((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(1)).get("subcategories")).get(0)).get("CategoryName"))); System.out.println(((String)((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(1)).get("subcategories")).get(0)).get("CategoryImage"))); System.out.println((((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(1)).get("subcategories")).get(0)).get("hassubcategories"))); System.out.println((((Document)((ArrayList)((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(1)).get("subcategories")).get(0)).get("subcategories")).get(0)).get("id"))); System.out.println(((String)((Document)((ArrayList)((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(1)).get("subcategories")).get(0)).get("subcategories")).get(0)).get("CategoryName"))); System.out.println(((String)((Document)((ArrayList)((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(1)).get("subcategories")).get(0)).get("subcategories")).get(0)).get("CategoryImage"))); System.out.println((((Document)((ArrayList)((Document)((ArrayList)((Document)((ArrayList)root.get("subcategories")).get(1)).get("subcategories")).get(0)).get("subcategories")).get(0)).get("hassubcategories")));