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Nested JSONArray

I need to read a JSON file with following form:
{
"Data":[{
"foo":"22",
"bar":"33",
"array":[
{
"1foo":"22",
"1bar":"33"
},
{
"2foo":"22",
"2bar":"33",
}
],
"anotherData":{
"foofoo":"22",
"barbar":"33"
},
"some more data":"11",
"some more data":"11"
},
{and the cycle here starts again from -->
"foo":"22",
"bar":"33",
"array":[
My question stands : How do I access individual elements given it's sometimes JSONObject and sometimes JSONArray. I tried using org.json library but I'm failing to access anything after this line -> "array":[. I tried various combinations of JSONObject and JSONArray up to no avail.
My latest code looked something like this:
List<Data> data= new ArrayList<>();
String rawJson = getJsonAsString();
JSONObject outer = new JSONObject(rawJson);
JSONArray jArr= outer.getJSONArray("Data");
JSONObject inner= outer.getJSONObject("array");
for(int i =0; i<jArr.length(); i++){
JSONObject jsonEvent = jArr.getJSONObject(i);
String foo = jsonEvent.getString("foo"); <-- this works,
String 1foo = jsonEvent.getString("1foo"); <-- but this doesn't and i cant access it
I tried dozens of different solutions(tried myself and tried to find something here as well, but every case with those nested arrays is different and I can't add those solutions together to get answer for my case)

You can increase your readability if you beautify your raw JSON string:
{
"Data":[
{
"foo":"22",
"bar":"33",
"array":[
{
"1foo":"22",
"1bar":"33"
},
{
"2foo":"22",
"2bar":"33"
}
],
"anotherData":{
"foofoo":"22",
"barbar":"33"
},
"some more data":"11",
"some more data":"11"
},
{ and the cycle here starts again from -->
"foo":"22",
"bar":"33",
"array":[
...
],
...
}
]
}
So, stick to the following code:
JSONArray jArr = outer.getJSONArray("Data");
jArr is now filled with array of your Object.
And to loop through your Object array, you can use a for-loop which you have done it correctly.
for (int i = 0; i < jArr.length(); i++) {
// The below gets your Object
JSONObject jsonEvent = jArr.getJSONObject(i);
}
And now each jsonEvent contains your Object, which you can access the Object by their type.
For example, if you would like to access foo, you can use:
String foo = jsonEvent.getString("foo"); // foo = "22"
String bar = jsonEvent.getString("bar"); // bar = "33"
// Note that your array is another Array, you need to get it as JSONArray first
JSONArray arrayJson = jsonEvent.getJSONArray("array");
And as 1foo is in the first Object for your array, you need to access it like this:
JSONObject firstObjectInArray = arrayJson.getJSONObject(0);
String target = firstObjectInArray.getString("1foo"); // target = "22"
And to access foofoo, as it is an attribute of the JSON Object anotherData, so you should obtain anotherData as JSONObject first, and then you can access foofoo:
JSONObject anotherDataObject = jsonEvent.getJSONObject("anotherData");
String foofoo = anotherDataObject.getString("foofoo"); // foofoo = "22"
So the full code within your for-loop should look like this:
for (int i = 0; i < jArr.length(); i++) {
// The below gets your Object
JSONObject jsonEvent = jArr.getJSONObject(i);
String foo = jsonEvent.getString("foo");
JSONArray arrayJson = jsonEvent.getJSONArray("array");
String target = arrayJson.getJSONObject(0).getString("1foo");
// Add to get foofoo
JSONObject anotherDataObject = jsonEvent.getJSONObject("anotherData");
String foofoo = anotherDataObject.getString("foofoo");
}

Parse only particular fields in JSON at once

I have a huge JSON but I only need to parse specific fields. I know paths to these fields so I decided to try JPath and it works but I want to parse all fields at once.
Let's say I have such JSON:
{
"data": [
{
"field1": 1,
"field2": 1,
...
"another_data": [ {
"required_field1": "1",
"required_field2": "2"
}
],
...
}
]
}
I want to get only required fields with these paths and map it to Java POJO:
$.data[*].another_data[*].required_field1
$.data[*].another_data[*].required_field2
So as a final result I want to have a list of Java objects, where the object contains required_field1 and required_field2.
UPD:
how it works now
I have a Java POJO that's a container
class RequiredInfo {
private String field1;
private String field2;
//constructor, setters, etc
}
I read JSON path 2 times by using JPath:
String json = "...";
Object document = Configuration.defaultConfiguration().jsonProvider().parse(json);
List<String> reqFields1 = JsonPath.read(document, "$.data[*].another_data[*].required_field1");
List<String> reqFields2 = JsonPath.read(document, "$.data[*].another_data[*].required_field2")
and then I map it to my POJO
for (int i = 0; i < reqFields1.size(); i++) {
res.add(new RequiredInfo(reqFields1.get(i), reqFields2.get(i)));
}
bit I think there is a better way how I can do it

You can try by creating a JSON object and get data:
JSONObject yourJsonObject = (JSONObject) new JSONParser().parse(yourJson);
JSONObject data = (JSONObject) yourJsonObject.get("data");
JSONObject data0 = (JSONObject) data.get(0);
JSONObject another_data = (JSONObject) data0.get("another_data");
String required_field1 = another_data.get("required_field1").toString();
String required_field2 = another_data.get("required_field2").toString();
Now that you have values, you can add them in your POJOs.

extract from JSON

"biodata": {
"Ruby": {
"Expertise": "web development",
"EXperience": "5 years"
},
"Dylon": {
"Expertise": "Java",
"EXperience": "2 years"
}
}
I have the above JSONObject . I am trying to fetch some keys here .
I am looking to fetch the name key i.e Ruby , Dylon etc .
I am then trying to fetch the "Experience " key value .
Desired output :
name= Ruby
Experience = 5 years
My code :
JSONParser parser = new JSONParser();
Object obj = parser.parse(new FileReader("path to JSON file"));
JSONObject jsonobj = (JSONObject) obj;
String statistics = jsonobj.getString("biodata"); //The method getString(String) is undefined for the type JSONObject
for (Iterator key = jsonobj.keys(); itr.hasNext();) {//The method keys() is undefined for the type JSONObject //itr cannot be resolved
JSONObject name = jsonobj.get(key.next()); //Type mismatch: cannot convert from Object to JSONObject
String key = key.next();//The method next() is undefined for the type String
JSONObject name = jsonobj.get(key); //Type mismatch: cannot convert from Object to JSONObject
Log.d("data", "key="+key+ " and value="+jsonobj.toString()); //Log cannot be resolved
}
I have mentioned the errors in the comment of my code .

You json is not valid .
You should change to this .
{
"biodata": {
"Ruby": {
"Expertise": "web development",
"EXperience": "5 years"
},
"Dylon": {
"Expertise": "Java",
"EXperience": "2 years"
}
}
}
Try this .
private void jsonParse() {
try {
// use jsonobject to parse json with
JSONParser parser = new JSONParser();
Object obj = parser.parse(new FileReader("path to JSON file"));
JSONObject jsonObject = (JSONObject) obj;
// get jsonobject by biodata tag
JSONObject biodata = jsonObject.getJSONObject("biodata");
// use Iterator to get name
Iterator<String> names = biodata.keys();
// use while loop
while (names.hasNext()) {
// get name
String name = names.next().toString();
Log.d("data", "name=" + name);
// get jsonobject by name tag
JSONObject nameJsonObject = biodata.getJSONObject(name);
// get string
String Expertise = nameJsonObject.getString("Expertise");
String EXperience = nameJsonObject.getString("EXperience");
Log.d("data", "Experience =" + EXperience);
}
} catch (JSONException e) {
e.printStackTrace();
}
}

You have many issues in your code.
First: Assuming you want to implement code based on your current JSON String
Issues:
JSONObject API do not facilitate the methods of Map used in your implementation.
Your JSON String is not a array so for loop is not going to help, instead you should fetch the inner JSONObjects using the getJSONObject () method of the JSONObject API.
Casting the parsed object from your parser API will not automatically make it a JSONObject, the right way of doing this as below:
JsonObject jsonObject = parser.parse(new FileReader("path to JSON file")).getAsJsonObject();
Second: Assuming you intent to implement the JSON string representation as array, you should correct your JSON string as below.
"biodata": [{ "Ruby": { "Expertise": "web development", "EXperience": "5 years" }}, {"Dylon": { "Expertise": "Java", "EXperience": "2 years" } }]
With the above JSON string you can implement the fetching of data logic using JSONArray API

How to parse a JSON string using ggson to get field values

I have a sample JSON as below. I need to get the individual fields like ASIdentifer and ExternalIdentifer. I have stored this JSON data in a string.
Using GoogleJson as the module(ggson)
JSON data:
{
"DeviceCommon": {
"ASIdentifier": "123",
"DatadeliveyMechanism": "notify",
"MobileOriginatorCallbackReference": {
"url": "http://application.example.com/inbound/notifications/modatanotification/"
},
"AccessiblityCallbackReference": {
"url": "http://application.example.com/inbound/notifications/accessibilitystatusnotification"
}
},
"DeviceList": [{
"ExternalIdentifer": "123456#mydomain.com",
"msisdn": "123456",
"senderName": "Device1",
"MobileOriginatorCallbackReference": {
"notifyURL": "http://application.example.com/inbound/notifications/modatanotification/"
},
"ConfigurationResultCallbackReference": {
"notifyURL": "http://application.example.com/inbound/notifications/configurationResult"
},
"ASreferenceID": "AS000001",
"NIDDduration": "1d"
}]
}
I created the POJO classes and parsed the data using below code
data = new Gson().fromJson(new FileReader("/home/raj/apache-tomcat-8.0.3/webapps/file.json"), Data.class);
System.out.println(data);
Output:
Data{
deviceCommon=DeviceCommon{
asIdentifier='123'
datadeliveyMechanism='notify'
mobileOriginatorCallbackReference=http://application.example.com/inbound/notifications/modatanotification/
accessiblityCallbackReference=http://application.example.com/inbound/notifications/accessibilitystatusnotification
}
deviceList=[DeviceListEntry{
externalIdentifer='123456#mydomain.com'
msisdn='123456'
senderName='Device1'
mobileOriginatorCallbackReference=http://application.example.com/inbound/notifications/modatanotification/
configurationResultCallbackReference=http://application.example.com/inbound/notifications/configurationResult
asReferenceID='AS000001'
nidDduration='1d'
}]
}
String jsonInString = gson.toJson(data);
System.out.println("String is"+ jsonInString);
Output:
String is{"DeviceCommon":{"ASIdentifier":"123","DatadeliveyMechanism":"notify","MobileOriginatorCallbackReference":{"url":"http://application.example.com/inbound/notifications/modatanotification/"},"AccessiblityCallbackReference":{"url":"http://application.example.com/inbound/notifications/accessibilitystatusnotification"}},"DeviceList":[{"ExternalIdentifer":"123456#mydomain.com","msisdn":"123456","senderName":"Device1","MobileOriginatorCallbackReference":{"notifyURL":"http://application.example.com/inbound/notifications/modatanotification/"},"ConfigurationResultCallbackReference":{"notifyURL":"http://application.example.com/inbound/notifications/configurationResult"},"ASreferenceID":"AS000001","NIDDduration":"1d"}]}
I need to parse this JSON string to get individual fields like ExternalIdentifier and ASIdentifier.
I tried something like this but it is not working.
JsonObject jobj = new Gson().fromJson(jsonInString, JsonObject.class);
String result = jobj.get("ASIdentifier").toString();
System.out.println("value is"+ result);
Note: ExternalIdentifier is within the array, so I need to loop through the array to find it.
Can you please tell me what I'm doing wrong?

Possible solution:
String result = jobj.get("DeviceCommon").getAsJsonObject().get("ASIdentifier").getAsString();
System.out.println("ASIdentifier: "+ result);
JsonArray jsonArray = jobj.get("DeviceList").getAsJsonArray();
for (JsonElement device : jsonArray ) {
result = device.getAsJsonObject().get("ExternalIdentifer").getAsString();
System.out.println("ExternalIdentifer: "+ result);
}
Output:
ASIdentifier: 123
ExternalIdentifer: 123456#mydomain.com

public static void printJson(JsonElement jsonElement,String key) {
// Check whether jsonElement is JsonObject or not
if (jsonElement.isJsonObject()) {
Set<Entry<String, JsonElement>> ens = ((JsonObject) jsonElement).entrySet();
if (ens != null) {
// Iterate JSON Elements with Key values
for (Entry<String, JsonElement> en : ens) {
// System.out.println("##key is"+en.getKey() + " : ");
printJson(en.getValue(), en.getKey());
// System.out.println(en.getValue().getAsString());
// System.out.println(jsonElement.getAsString());
}
}
}
// Check whether jsonElement is Primitive or not
else if (jsonElement.isJsonPrimitive()) {
// print value as String
System.out.println("###key is"+key);
System.out.println("### value is"+jsonElement.getAsString());
}
else if (jsonElement.isJsonArray()) {
JsonArray jarr = jsonElement.getAsJsonArray();
// Iterate JSON Array to JSON Elements
System.out.println("\n###Array size is"+ jarr.size());
for (JsonElement je : jarr) {
printJson(je,key);
}
}
}

Extract json subset with few attributes from the main json

Is there an API/tool available for extracting specific attributes(json subset) of a json in java, similar to apache-commons beanutils copy?
For example I have the following JSON
{
"fixed":[
{
"b":"some value",
"c":"some value",
"d":"some value",
"e":"some value",
"f":"some value"
},
{
"b":"value",
"c":"value",
"d":"value",
"e":"value",
"f":"value"
}
]
}
I would like to have the following json
{
"fixed":[
{
"b":"some value",
"e":"some value",
"f":"some value"
},
{
"b":"value",
"e":"value",
"f":"value"
}
]
}
I came up the following method, but not sure if its the right approach
public JSONObject parseJSON(JSONObject data,List<String> subset){
JSONArray fixedArray = (JSONArray) data.get("fixed");
JSONObject resObj = new JSONObject();
JSONArray resArray = new JSONArray();
for(int i=0;i<fixedArray.size();i++){
JSONObject element = (JSONObject) fixedArray.get(i);
JSONObject resElement = new JSONObject();
for(String s:subset){
resElement.put(s, element.get(s));
}
resArray.add(resElement);
}
return resObj.put("fixed", resArray);
}
I had a look at this SO question, but wasn't helpful for this topic.

https://docs.oracle.com/javase/tutorial/jaxb/intro/arch.html you can also create you own pojo class from JAXB ,if you want.