Get the key value from a json in Java - JSON Parsing

Question

I have a json as below. I want to get mobile_number from this jsonObject.

json:-

{"id": "ABCD", "report": { "data": { "phone": { "mobile_number": 9876543210, "active": "Y", "content": null } } } }

I am doing it like this and it works fine but can someone help me with any other approach for it without getting every key.

JSONObject jsonObject = new JSONObject(json);
JSONObject report = getJSONObjectFromJson(jsonObject, "report");
JSONObject data = getJSONObjectFromJson(jsonObject, "data");
JSONObject phone = getJSONObjectFromJson(data, "phone");
long mobileNumber = getLongFromJson(phone, "mobile_number");

private Long getLongFromJson(JSONObject object, String key){
    return (object !=null && object.has(key)) ? object.getLong(key) : null;
}

private JSONObject getJSONObjectFromJson(JSONObject object, String key){
    return (object !=null && object.has(key)) ? object.getJSONObject(key) : null;
}

You could use a json mapper as gson for example. In this case you only define objects with the properties you want to access and apply the parse method — jeprubio
– jeprubio, Commented Nov 15, 2019 at 8:02
There isn't a way to do it without traversing the tree, one way or another. — NiVeR
– NiVeR, Commented Nov 15, 2019 at 8:02
I think the value of mobile_number should be wrapped by double quotes because it may starts with 0 which makes your JSON string be invalid. — LHCHIN
– LHCHIN, Commented Nov 15, 2019 at 8:28

Artyom Rebrov · Accepted Answer · 2019-11-15 08:06:35Z

2

I've just dealing with the similar issue and decided to use JsonPath like this:

final DocumentContext jsonContext = JsonPath.parse(jsonString);
final Object read = jsonContext.read("$['report']['data']['phone']['mobile_number']");

answered Nov 15, 2019 at 8:06

Artyom Rebrov

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Comments

user9544895 · Accepted Answer · 2019-11-15 08:24:35Z

You can use Jackson ObjectMapper.

        try {
            ObjectMapper mapper = new ObjectMapper();
            String jsonString = "{\"id\": \"ABCD\", \"report\": { \"data\": { \"phone\": { \"mobile_number\": 9876543210, \"active\": \"Y\", \"content\": null } } } }";
            JsonNode rootNode = mapper.readTree(jsonString);

            JsonNode mobileNumber = rootNode.path("report").path("data").path("phone").path("mobile_number");
            System.out.println("Mobile Number: " + mobileNumber.longValue());

        } catch (JsonParseException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

Ankush Sharma · Accepted Answer · 2020-08-25 09:03:16Z

So there are lot of ways to do it but everything leads eventually to traversing the tree.

So to conclude all the approaches,

1. **Convert string to JsonObject and traverse.** 

    JSONObject jsonObject = new JSONObject(json);
    JSONObject report = getJSONObjectFromJson(jsonObject, "report");
    JSONObject data = getJSONObjectFromJson(jsonObject, "data");
    JSONObject phone = getJSONObjectFromJson(data, "phone");
    long mobileNumber = getLongFromJson(phone, "mobile_number");
    
    private Long getLongFromJson(JSONObject object, String key){
        return (object !=null && object.has(key)) ? object.getLong(key) : null;
    }
    
    private JSONObject getJSONObjectFromJson(JSONObject object, String key){
        return (object !=null && object.has(key)) ? object.getJSONObject(key) : null;
    }

 2. **Using jackson objectMapper to get the JsonNode and then traverse.**

    ObjectMapper mapper = new ObjectMapper();
    JsonNode jsonNode= mapper.readTree(json);
    JsonNode mobileNumber = jsonNode.path("report").path("data").path("phone").path("mobile_number");

 3. **Using gson jsonmapper to convert to map and then iterate the map.**

    Gson gson = new Gson();
    Map map = gson.fromJson(json, Map.class);

marcoreus · Accepted Answer · 2019-11-15 08:08:37Z

0

jsonObject.getJSONObject("x").getJSONObject("Y").getJSONObject("z");

Another route would be to leverage the ObjectMapper.

answered Nov 15, 2019 at 8:08

marcoreus

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