JSON-Simple. Append to a JSONArray

Question

I am using the JSON-simple library to parse the Json format. How can I append something to a JSONArray? For e.g. consider the following json

{
    "a": "b"
    "features": [{/*some complex object*/}, {/*some complex object*/}]
}

I need to append a new entry in the features. I am trying to create a function like this:-

public void appendToList(JSONObject jsonObj, JSONObject toBeAppended){

    JSONArray arr = (JSONArray)jsonObj.get("features");

    //1) append the new feature
    //2) update the jsonObj
}

How to achieve steps 1 & 2 in the above code?

Sachin Gupta · Accepted Answer · 2015-05-04T11:00:25.837

4

You can try this:

public static void main(String[] args) throws ParseException {

    String jsonString = "{\"a\": \"b\",\"features\": [{\"feature1\": \"value1\"}, {\"feature2\": \"value2\"}]}";
    JSONParser parser = new JSONParser();
    JSONObject jsonObj = (JSONObject) parser.parse(jsonString);

    JSONObject newJSON = new JSONObject();
    newJSON.put("feature3", "value3");

    appendToList(jsonObj, newJSON);

    System.out.println(jsonObj);
    }


private static void appendToList(JSONObject jsonObj, JSONObject toBeAppended) {

        JSONArray arr = (JSONArray) jsonObj.get("features");        
        arr.add(toBeAppended);
    }

This will fulfill your both requirements.

edited May 04 '15 at 11:00

answered May 04 '15 at 10:52

Sachin Gupta

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this does not satisfy the method signature i have provided above. – ishan3243 May 04 '15 at 10:54
Instead of creating a new `JSONObject` instance, just add the 2nd argument in the method to the `arr` using the `put` call. – asgs May 04 '15 at 10:57
this is not what I meant. Just assume that I don't have any information what is inside the "complex object" I have mentioned above – ishan3243 May 04 '15 at 11:00
The information of complex object is not needed as you have to add a new entry in JSONArray, As shown above you can add it using `add` method. – Sachin Gupta May 04 '15 at 11:02
does adding it to the array update the original jsonObj? – ishan3243 May 04 '15 at 11:04
Yes it will, I have printed original obj after method call. It is adding the same. – Sachin Gupta May 04 '15 at 11:05

ItayB · Answer 2 · 2015-05-04T11:35:35.860

-1

Getting the array by: jsonObj["features"], then you can add new item by assign it as the last element in the array ( jsonObj["features"].length is the next free place to add new element)

jsonObj["features"][jsonObj["features"].length] = toBeAppended;

fiddle example

edited May 04 '15 at 11:35

answered May 04 '15 at 10:46

ItayB

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OP is asking for an example in json-simple, not javascript. – shahkalpesh May 04 '15 at 10:50
While this source code may provide an answer, a few words of explanation would benefit current and future readers. – Thom May 04 '15 at 11:18
@TheThom I've added some explanation, thanks for your comment – ItayB May 04 '15 at 11:36

JSON-Simple. Append to a JSONArray

2 Answers2