Add a key value in json file using java

Question

I have a json file which look like as below.

 {
  "List": [
    {
      "C1": "A",
      "C2": "mail1",
      "C3": "1"
    },
    {
      "C1": "B",
      "C2": "mail2",
      "C3": "2"
    },
    {
      "C1": "C",
      "C2": "mail3",
      "C3": "3"
    },
    {
      "C1": "D",
      "C2": "mail4",
      "C3": "4"
    }
  ]
}

I wanted to add a key value to this json file.It should look like this.

  {
      "List": [
        {
          "C0": "I1",
          "C1": "A",
          "C2": "mail1",
          "C3": "1"
        },
        {
          "C0": "I2",
          "C1": "B",
          "C2": "mail2",
          "C3": "2"
        },
        {
          "C0": "I3",
          "C1": "C",
          "C2": "mail3",
          "C3": "3"
        },
        {
          "C0": "I4",
          "C1": "D",
          "C2": "mail4",
          "C3": "4"
        }
      ]
}

How can we achieve this in java8.I have tried with the jackson-all-1.9.0 jar but it is adding key value at last.Help is appriciated.

you cannot change the order in an existing map. It preserves the insertion order. One thing you can try out is by, creating a new map by putting the new key value pair and then put all the key values from the original map to the newly created map — Nishad K Ahamed
– Nishad K Ahamed, Commented Oct 13, 2017 at 9:35
Show us the code with which you tried to do it with jackson. It's hard to help you fix the code we can't see — Milo Bem
– Milo Bem, Commented Oct 13, 2017 at 9:35

Chandan kushwaha · Accepted Answer · 2017-10-13 09:40:44Z

1

You can achieve this in the following way.

try {

        JSONObject objs = new JSONObject("{\"List\":[\n" +
                "{\"C1\":\"A\",\"C2\":\"mail1\",\"C3\":\"1\"},\n" +
                "{\"C1\":\"B\",\"C2\":\"mail2\",\"C3\":\"2\"},\n" +
                "{\"C1\":\"C\",\"C2\":\"mail3\",\"C3\":\"3\"},\n" +
                "{\"C1\":\"D\",\"C2\":\"mail4\",\"C3\":\"4\"}\n" +
                "]}");

        JSONArray jsonArray=objs.getJSONArray("List");
        for (int i = 0; i < jsonArray.length(); i++) {
            JSONObject obj = jsonArray.getJSONObject(i);
            obj.put("C0", "I" + (i + 1));
            jsonArray.put(i,obj);
        }
        Log.v("TAG_RESULT",jsonArray.toString());
    } catch (JSONException e) {
        e.printStackTrace();
    }

edited Oct 13, 2017 at 9:40

answered Oct 13, 2017 at 9:32

Chandan kushwaha

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12 Comments

Sachin Gupta Over a year ago

Have you compiled this code, this is not a JSONArray.

Chandan kushwaha Over a year ago

@SachinGupta Then what it is?

Sachin Gupta Over a year ago

It is a JsonObject

Chandan kushwaha Over a year ago

Have u seen the Code properly?

Chandan kushwaha Over a year ago

Getting The JSONObject from JSONArray and then adding the key and Updating the JSONArray

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