[Rest API][JsonPath] [GSON]-> How to Add a node to JSON in JAVA with JSONPath

 Recentally, I came across a situation, where I need to update my JSON with new node which can include jsonArray, JsonMap and just updating a node value.

My JSON was like this:

{
  "firstName": "John",
  "age": 26,
  "address": {
    "streetAddress": "naist street",
    "city": "Nara",
    "postalCode": "630-0192"
  }
}

And I was expecting it to be like this:

{
	"firstName": "John",
	"lastName": "Mathpal",
	"address": {
		"streetAddress": "naist street",
		"city": "Ranikhet",
		"postalCode": "630-0192",
		"landmark": "More Market"
	},
	"age": 26.0,
	"vehicle": {
		"name": "honda",
		"model": "GS",
		"price": "15.8 L"
	},
	"phoneDetails": [{
		"type": "iphone",
		"number": "123"
	}, {
		"type": "android",
		"number": "456"
	}]
}

So this first change, I was expecting to change the value of city from "Nara" to "Ranikhet".

So to implement it, I used JSONPath DocumentContext which have the set method to set a node value.

So first I read the json file:

String requestBody = readRequestBody(path);

private static String readRequestBody(String requestBodyPath) throws IOException {
    File requestBody = new File(requestBodyPath);
    return JsonPath.parse(requestBody).jsonString();
}

String valueToBeAddedUpdated = "Ranikhet";
String nodeWhereValueNeedToUpdate = "$.address.city";
requestBody = setJsonDataValue(nodeWhereValueNeedToUpdate, valueToBeAddedUpdated, requestBody);

so to set the value:

private static String setJsonDataValue(String nodeWhereValueNeedToUpdate, Object valueToBeAddedUpdated, String requestBody) {
    return JsonPath.parse(requestBody).set(nodeWhereValueNeedToUpdate, valueToBeAddedUpdated).jsonString();
}

It sets the value in the json for city value to :

{

"firstName": "John",

"age": 26,

"address": {

"streetAddress": "naist street",

"city": "Ranikhet",

"postalCode": "630-0192"

}

}

After settign the value, I added a node "lastName": "Mathpal",

requestBody = addJsonNode("$","lastName", "Mathpal",requestBody);

private static String addJsonNode(String jsonpath, String nodeName, String nodeValue, String requestBody) {
    DocumentContext documentContext = JsonPath.parse(requestBody);
    documentContext.put(JsonPath.compile(jsonpath), nodeName,  nodeValue);
    String updatedRequestBody = documentContext.jsonString();
    return updatedRequestBody;
}

After setting the value, I added a node inside the address: "landmark": "More Market"

requestBody = addJsonNode("$.address","landmark", "More Market",requestBody);

Once this is added, I tried to add a JSONMap vehicle to the existing json.

So to set it, I first prepared a map with vehicle and its details.

String nodeName = "vehicle";
Map<String, Object> finalMap = prepareJsonMapForVehicle(nodeName);

private static Map<String, Object> prepareJsonMapForVehicle(String nodeName) {
    Map<String, Object> finalMap = new LinkedHashMap<>();
    Map<String, Object> vehicleMap = new LinkedHashMap<>();
    vehicleMap.put("name", "honda");
    vehicleMap.put("model", "GS");
    vehicleMap.put("price", "15.8 L");
    finalMap.put(nodeName, vehicleMap);
    return finalMap;
}

Once that is done, I used GSON to add that map to the existign requestBody.

requestBody = addJsonMap(requestBody, finalMap);

private static String addJsonMap(String requestBody, Map<String, Object> finalMap) {
    HashMap<String, Object> map = new Gson().fromJson(requestBody, HashMap.class);
    map.putAll(finalMap);
    return new Gson().toJson(map);
}

GSON have 2 methods fromJSON and toJSON which helps to convert java map to json and vice versa.

Once that is done, now added the json array "phoneDetails" field.

So to add it, i first created the jsonArray field as an jsonArray.

String nodeName1 = "phoneDetails";
JsonArray phoneDetails = new JsonArray();

And then added that JSONArray to existing json with the help of JSONPath put method.

 String nodeName1 = "phoneDetails";

JsonArray phoneDetails = new JsonArray();
requestBody =addJsonNodeAsArray("$", nodeName1,phoneDetails,requestBody);

in the addJsonNodeAsArray method, I used the JSONPath put method to set the value.

private static String addJsonNodeAsArray(String jsonpath, String nodeName, JsonArray nodeValue, String requestBody) {
    DocumentContext documentContext = JsonPath.parse(requestBody);
    documentContext.put(JsonPath.compile(jsonpath), nodeName,  nodeValue);
    String updatedRequestBody = documentContext.jsonString();
    return updatedRequestBody;
}

Once the json Array is added, we cans et value for it.

requestBody = addJsonArrayValues("$.phoneDetails", requestBody,  "iphone", "123") ;
System.out.println("-------------------------------------------------------------------------------------------");

The only change in this method is, that it takes a map while adding. 

private static String addJsonArrayValues(String jsonPath, String requestBody, String arrayNodeName, String arrayNodeValue) {
    DocumentContext documentContext= JsonPath.parse(requestBody);
    documentContext.add(JsonPath.compile(jsonPath),prepareJsonMapForPhone(arrayNodeName, arrayNodeValue));
    String latestIne = documentContext.jsonString();
    return latestIne;
}

Once that is done, we can add another json value inside into it too.

requestBody = addJsonArrayValues("$.phoneDetails", requestBody,  "android", "456") ;
System.out.println("After adding another value to the jsonArray inside a json:" +requestBody);

This is how I update a json value, added a new json node with value, a json array and a jsonMap into an existing JSON.