Create merged JSON with GSON

Question

I've found tons of examples of using GSON to convert either an single object, or a list of that single object, to its respective JSON. Quite easy to do. Even if the object has objects as its properties, this still is trivial.

But let's say I have 5 objects of interest (names, companies, colors, numbers, candy) and they have no relationship to each other at all. So I make my database calls, and now have 5 lists full of all of the above in my code.

Now, how could I put these lists into a JSON Array whose parent name is "items" and contains all of the above as children beneath it? So one parent "items", with 5 children (each child is a sibling of each other).

What is the appropriate way using GSON (or not??) to construct such a tree or structure? I noticed there is a lot in GSON such as JSONArray and such, but wasn't able to figure it out.

Thanks so much!

Please clarify. My understanding is that you want to encapsulate all the data into one JSON object. It seems like creating a custom serializer may be the solution. — Aarowaim, Apr 03 '14 at 03:58

Luis Lavieri · Accepted Answer · 2015-04-30T22:01:08.500

Yes, you can. You have to build your own serializer first. For instance:

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;


public static String toJson(List<Item> items){

    try{

        JSONObject jsonObj = new JSONObject();

        JSONArray jsonArr = new JSONArray();

        for(Item i : items){
            JSONObject itemObj = new JSONObject();
            itemObj.put("names", i.getName());
            itemObj.put("companies", i.getCompanies());
            itemObj.put("colors", i.getColors());
            itemObj.put("numbers", i.getNumbers());
            itemObj.put("candy", i.getCandy());
            jsonArr.put(itemObj);
        }

        jsonObj.put("items", jsonArr);

        return jsonObj.toString();

    } catch(JSONException ex){
         ex.printStackTrace();
    }

    return null;
}

I will try this tonight, but I suspect this will do the trick. Very concise too. Thanks! — NullHypothesis, Apr 03 '14 at 13:35
Sure, no problem! I just edited my code because I forgot to add one line at the end of the `for` loop. Be aware of it. It is really important :) — Luis Lavieri, Apr 03 '14 at 19:22

score 0 · Answer 2 · answered Apr 03 '14 at 04:45

Depending on what the fields are, you can make a model class and set the objects from database. The use Gson and form your Json string using jsonFrom.

Eg.

public class Items{

ArrayList<String> names;

String candy;

//nested custom class if necessary
ArrayList<Companies> companies;

//other fields here 

//getter setter
}

Now set the values for objects of Items.

Then:

Gson gson = new Gson();
String json = gson.toJson(modelClassObject);

If i got your requirement right, json is the String you need.

score 0 · Answer 3 · answered Oct 03 '18 at 07:37

0

To merge JSONs you need to define some conventions of merging. If "Overlay" strategy (replace or add) conforms you, you can find a helpful JSON Merging Library in this answer.

answered Oct 03 '18 at 07:37

Zon

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Create merged JSON with GSON

3 Answers3