Develop Reference

How can i convert this JSON to Java Object?

I'm learning JACKSON. To train my skills i want to get field "URL" from following JSON:
How can i do that? I don't need whole JSON-object, just one field (URL).

You don't need to convert the JSON into a Java Object for that you will need to define POJOS.
Maybe this will help :-
final ObjectNode yourNode = new ObjectMapper().readValue(<Your_JSON_Input_String>, ObjectNode.class);
if (node.has("URL")) {
System.out.println("URL :- " + node.get("URL"));
}

import org.json.JSONArray;
import org.json.JSONObject;
public class Main {
public static void main(String[] args) throws IOException {
String jsonString = "{\"data\":[{\"url\":\"http://example.com\"}]}";
JSONObject jsonObject = new JSONObject(jsonString); // 1
JSONArray data = jsonObject.getJSONArray("data"); // 2
JSONObject objectAtIndex0 = data.getJSONObject(0); // 3
String urlAtObject0 = objectAtIndex0.getString("url"); // 4
System.out.println(urlAtObject0);
}
}
Get JSON object for whole JSON string
Get data as JSON array
Get JSON object at desired index or loop on JSON array of previous step
Get url field of the JSON object

count key value in JSON and extract values

I have following JSONObject (not array, which I don't mind to convert). I am trying to do two things:
get the count of genre entry as "poetry" (count = 2).
get the key value of author name and genre:
authorName = malcolm
genreName = newsarticle
authorName = keats
genreName = poetry
{ "AddressBook" :{
"Details" :{
"authorname" :{
"Author-malcolm":{
"genre" :"poetry"
}
"Author-keats":{
"genre" :"poetry"
}
}
}
}
}
Code which I tried:
public static void main(String[] args) throws Exception, IOException, ParseException {
JSONParser parser = new JSONParser();
Object obj = parser.parse(new FileReader("My path to JSON"));
JSONObject jsonObject = (JSONObject) obj;
JSONArray arrayhere = new JSONArray();
arrayhere.add(obj);
System.out.println(arrayhere);
int count = 0;
for(int i = 0; i < arrayhere.size(); i++) {
JSONObject element = arrayhere.getJSONObject(i);//The method getJSONObject(int) is undefined for the type JSONArray
String branchName = element.getString("genre");//The method getString(String) is undefined for the type JSONObject
if(branchName.equals("poetry")) {
count ++;
}
}
System.out.println("Count f0r poetry genre=" + count);
}
}
I have looked at solutions all over. There is no question similar to this at stackoverflow. I am not sure if the procedure is correct.

A few problems here.
First, I'm not sure where you got that example JSON but you can't work with that. That's not even valid JSON Formatting.
Looks like you want something like this:
{
AddressBook:
[
{
authorname: "author-malcom",
genre:"poetry"
},
{
authorname: "author-keats",
genre: "poetry"
}
]
}
That's the structure you're trying to create in JSON.
So, you're parsing this in from a file into a JSONObject that has a key called AddressBook inside of it. That key points to an array of JSONObjects representing authors. Each of those objects will have a key called genre. You're trying to access the genre key and count on a condition.
What you did above was create attempt to create a JSONObject from an invalid string, and then add the entire JSONObject itself into the JSONArray. JSONArray.add() doesn't convert an object to an array, it literally adds it onto the array.
jsonObj => {"Name":"name1","Id":1000}
jsonArray.add(jsonObj)
jsonArray => [{"Name":"name1","Id":1000}]
That's what you did in your code above. You didn't create an array from a JSONObject, you added an object to the array.
Proper use is going to look like:
Object obj = parser.parse(new FileReader("path_to_file"));
JSONObject jobj = (JSONObject) obj;
//access key AddressBook
JSONArray author_array = jobj.getJSONArray("AddressBook");
int poetry = 0;
for(int i = 0; i < author_array.length(); i++) {
JSONObject author = (JSONObject) author_array.get(i);
if(author.getString("genre").equals("poetry")) {
poetry++;
}
}
To summarize, you're problems come from a lack of understanding about JSON Formatting and how to access elements within a JSON Object.
Paste in the sample JSONObject I gave you above here. That site will let you visualize what you're working with.

ArraysList as JSON

I wrote the below code in order for me to output a ArrayList as JSON. When I ran the code I get the output as shown below:
{uniteids:=[{"UniteId:":"gsheetyr","Message:":" The given user is already a member of the given DL.,"},{"UniteId:":"spokuri ","Message:":" The given user is already a member of the given DL.,"}]}
But, I wanted the output to be in the below format. Can you please let me know what changes I need to make to my code?
{"uniteids":[{"UniteId:":"gsheetyr","Message:":" The given user is already a member of the given DL.,"},{"UniteId:":"spokuri ","Message:":" The given user is already a member of the given DL.,"}]}
Code:
package com.uniteid.controller;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.json.JSONArray;
public class JsonResponse {
public static void main(String[] args) {
List<String> retStatus = new ArrayList<String>();
Map<String, String> stat = new HashMap<String, String>();
String jsonInString = "NORESPONSE";
String jsonInString2 = "";
Map<String, String> uniteidshashMap = new HashMap<String, String>();
JSONArray ja = new JSONArray();
retStatus.add("gsheetyr: The given user is already a member of the given DL.,");
retStatus.add("spokuri : The given user is already a member of the given DL.,");
if (retStatus.size() > 0) {
for (int i = 0; i < retStatus.size(); i++) {
String splited[] = retStatus.get(i).split("\\:");
stat.put("UniteId:", splited[0]);
stat.put("Message:",splited[1]);
ja.put(stat);
System.out.println(ja);
}
jsonInString = ja.toString();
uniteidshashMap.put("uniteids:", jsonInString);
jsonInString2 = uniteidshashMap.toString();
System.out.println(jsonInString2);
}
}
}

Try this
JSONArray arrayHolder = new JSONArray();
if (retStatus.size() > 0) {
for (int i = 0; i < retStatus.size(); i++) {
String splited[] = retStatus.get(i).split("\\:");
JSONObject innerObj = new JSONObject();
innerObj.put("UniteId:", splited[0]);
innerObj.put("Message:",splited[1]);
arrayHolder.put(innerObj);
}
JSONObject finalObject = new JSONObject();
finalObject.put("uniteids:", arrayHolder);
System.out.println(finalObject.toString());
}

I believe if you wrap your uniteidshashMap object inside a JsonArray and call toString() on that instead, you'll get a better result.

json.org Java: JSON array parsing bug [duplicate]

This question already has answers here:
How to parse JSON in Java
(36 answers)
Closed 4 years ago.
I have JSON object as follows:
member = "{interests : [{interestKey:Dogs}, {interestKey:Cats}]}";
In Java I want to parse the above json object and store the values in an arraylist.
I am seeking some code through which I can achieve this.

I'm assuming you want to store the interestKeys in a list.
Using the org.json library:
JSONObject obj = new JSONObject("{interests : [{interestKey:Dogs}, {interestKey:Cats}]}");
List<String> list = new ArrayList<String>();
JSONArray array = obj.getJSONArray("interests");
for(int i = 0 ; i < array.length() ; i++){
list.add(array.getJSONObject(i).getString("interestKey"));
}

public class JsonParsing {
public static Properties properties = null;
public static JSONObject jsonObject = null;
static {
properties = new Properties();
}
public static void main(String[] args) {
try {
JSONParser jsonParser = new JSONParser();
File file = new File("src/main/java/read.json");
Object object = jsonParser.parse(new FileReader(file));
jsonObject = (JSONObject) object;
parseJson(jsonObject);
} catch (Exception ex) {
ex.printStackTrace();
}
}
public static void getArray(Object object2) throws ParseException {
JSONArray jsonArr = (JSONArray) object2;
for (int k = 0; k < jsonArr.size(); k++) {
if (jsonArr.get(k) instanceof JSONObject) {
parseJson((JSONObject) jsonArr.get(k));
} else {
System.out.println(jsonArr.get(k));
}
}
}
public static void parseJson(JSONObject jsonObject) throws ParseException {
Set<Object> set = jsonObject.keySet();
Iterator<Object> iterator = set.iterator();
while (iterator.hasNext()) {
Object obj = iterator.next();
if (jsonObject.get(obj) instanceof JSONArray) {
System.out.println(obj.toString());
getArray(jsonObject.get(obj));
} else {
if (jsonObject.get(obj) instanceof JSONObject) {
parseJson((JSONObject) jsonObject.get(obj));
} else {
System.out.println(obj.toString() + "\t"
+ jsonObject.get(obj));
}
}
}
}}

Thank you so much to #Code in another answer. I can read any JSON file thanks to your code. Now, I'm trying to organize all the elements by levels, for could use them!
I was working with Android reading a JSON from an URL and the only I had to change was the lines
Set<Object> set = jsonObject.keySet();
Iterator<Object> iterator = set.iterator();
for
Iterator<?> iterator = jsonObject.keys();
I share my implementation, to help someone:
public void parseJson(JSONObject jsonObject) throws ParseException, JSONException {
Iterator<?> iterator = jsonObject.keys();
while (iterator.hasNext()) {
String obj = iterator.next().toString();
if (jsonObject.get(obj) instanceof JSONArray) {
//Toast.makeText(MainActivity.this, "Objeto: JSONArray", Toast.LENGTH_SHORT).show();
//System.out.println(obj.toString());
TextView txtView = new TextView(this);
txtView.setText(obj.toString());
layoutIzq.addView(txtView);
getArray(jsonObject.get(obj));
} else {
if (jsonObject.get(obj) instanceof JSONObject) {
//Toast.makeText(MainActivity.this, "Objeto: JSONObject", Toast.LENGTH_SHORT).show();
parseJson((JSONObject) jsonObject.get(obj));
} else {
//Toast.makeText(MainActivity.this, "Objeto: Value", Toast.LENGTH_SHORT).show();
//System.out.println(obj.toString() + "\t"+ jsonObject.get(obj));
TextView txtView = new TextView(this);
txtView.setText(obj.toString() + "\t"+ jsonObject.get(obj));
layoutIzq.addView(txtView);
}
}
}
}

1.) Create an arraylist of appropriate type, in this case i.e String
2.) Create a JSONObject while passing your string to JSONObject constructor as input
As JSONObject notation is represented by braces i.e {}
Where as JSONArray notation is represented by square brackets i.e []
3.) Retrieve JSONArray from JSONObject (created at 2nd step) using "interests" as index.
4.) Traverse JASONArray using loops upto the length of array provided by length() function
5.) Retrieve your JSONObjects from JSONArray using getJSONObject(index) function
6.) Fetch the data from JSONObject using index '"interestKey"'.
Note : JSON parsing uses the escape sequence for special nested characters if the json response (usually from other JSON response APIs) contains quotes (") like this
`"{"key":"value"}"`
should be like this
`"{\"key\":\"value\"}"`
so you can use JSONParser to achieve escaped sequence format for safety as
JSONParser parser = new JSONParser();
JSONObject json = (JSONObject) parser.parse(inputString);
Code :
JSONParser parser = new JSONParser();
String response = "{interests : [{interestKey:Dogs}, {interestKey:Cats}]}";
JSONObject jsonObj = (JSONObject) parser.parse(response);
or
JSONObject jsonObj = new JSONObject("{interests : [{interestKey:Dogs}, {interestKey:Cats}]}");
List<String> interestList = new ArrayList<String>();
JSONArray jsonArray = jsonObj.getJSONArray("interests");
for(int i = 0 ; i < jsonArray.length() ; i++){
interestList.add(jsonArray.getJSONObject(i).optString("interestKey"));
}
Note : Sometime you may see some exceptions when the values are not available in appropriate type or is there is no mapping key so in those cases when you are not sure about the presence of value so use optString, optInt, optBoolean etc which will simply return the default value if it is not present and even try to convert value to int if it is of string type and vice-versa so Simply No null or NumberFormat exceptions at all in case of missing key or value
From docs
Get an optional string associated with a key. It returns the
defaultValue if there is no such key.
public String optString(String key, String defaultValue) {
String missingKeyValue = json_data.optString("status","N/A");
// note there is no such key as "status" in response
// will return "N/A" if no key found
or To get empty string i.e "" if no key found then simply use
String missingKeyValue = json_data.optString("status");
// will return "" if no key found where "" is an empty string
Further reference to study
How to convert String to JSONObject in Java
Convert one array list item into multiple Items

There are many JSON libraries available in Java.
The most notorious ones are: Jackson, GSON, Genson, FastJson and org.json.
There are typically three things one should look at for choosing any library:
Performance
Ease of use (code is simple to write and legible) - that goes with features.
For mobile apps: dependency/jar size
Specifically for JSON libraries (and any serialization/deserialization libs), databinding is also usually of interest as it removes the need of writing boiler-plate code to pack/unpack the data.
For 1, see this benchmark: https://github.com/fabienrenaud/java-json-benchmark I did using JMH which compares (jackson, gson, genson, fastjson, org.json, jsonp) performance of serializers and deserializers using stream and databind APIs.
For 2, you can find numerous examples on the Internet. The benchmark above can also be used as a source of examples...
Quick takeaway of the benchmark: Jackson performs 5 to 6 times better than org.json and more than twice better than GSON.
For your particular example, the following code decodes your json with jackson:
public class MyObj {
private List<Interest> interests;
static final class Interest {
private String interestKey;
}
private static final ObjectMapper MAPPER = new ObjectMapper();
public static void main(String[] args) throws IOException {
MyObj o = JACKSON.readValue("{\"interests\": [{\"interestKey\": \"Dogs\"}, {\"interestKey\": \"Cats\" }]}", MyObj.class);
}
}
Let me know if you have any questions.

How to Parse JSON with dynamic Keyname?

I have a JSON response like this.
{
"array": [
{
"object1": {
"aa": "somevalue1",
"bb": "somevalue2",
"cc": "somevalue3"
}
},
{
"object2": {
"aa": "somevalue4",
"bb": "somevalue5",
"cc": "somevalue6"
}
}
]}
Now I can get a JSON array from above response. I want read the value aa,bb,cc from object object1 and object2 in a for loop.
JSON is dynamic, I mean that object2 can also appear before object1 (in reverse order) and there is chances that I might get one more object(object3) with same structure OR only one (object1 or object2 or object3).
I dont want to do like this as I failed in :
JSONArray jsonArray = json.getJSONArray("array");
for (int i = 0; i < jsonArray.length(); i++)
{
JSONObject jsonObject = jsonArray.getJSONObject(i).getJSONObject("object1");
}
So my question is HOW can I read those values aa,bb,cc without depending on object name or number of object (object1 or object2 or object3)?

It looks like each item in the array only has 1 key/value pair which holds another json object which then has several.
If this is the case, then you could probably do something like this:
for (int i = 0; i < jsonArray.length(); i++)
{
JSONObject jsonObject = jsonArray.getJSONObject(i);
JSONObject innerObject = jsonObject.getJSONObject(jsonObject.keys().next().toString());
/// do something with innerObject which holds aa, bb, cc
}
You simply grab the 1st key in the wrapping object, and use that to grab the inner json object.

I think you should have next Java-side structure of classes:
Entity - class that will hold aa, bb and cc fields
Container - a class that will consist of two fields - Name and Entity, where Name can store object1, object2 or whatever.
Then, you should deserialize provided JSON into collection/array of Container entities.
Hope this helps.
Update: please check this example Collection deserialization

You should work with dynamic structures like java.util.Map. Try with this:
import java.util.List;
import java.util.Map;
import org.apache.commons.lang.StringUtils;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.type.TypeReference;
public class JsonTest {
public static void main(String[] args) {
String json = "{\"array\": [{\"object1\": {\"aa\": \"somevalue1\",\"bb\": \"somevalue2\",\"cc\": \"somevalue3\"}},{\"object2\": {\"aa\": \"somevalue4\",\"bb\": \"somevalue5\",\"cc\": \"somevalue6\"}}]}";
System.out.println(json);
final MyJson parseJsonSpecification = parseJsonSpecification(json);
System.out.println(parseJsonSpecification.array.get(0).get("object1"));
System.out.println(parseJsonSpecification);
}
public static MyJson parseJsonSpecification(String jsonString) {
try {
if (StringUtils.isBlank(jsonString)) {
return new MyJson();
}
MyJson ret;
ret = new ObjectMapper().readValue(jsonString, new TypeReference<MyJson>() {
});
return ret;
} catch (Exception ex) {
throw new IllegalArgumentException("La expresión '" + jsonString + "' no es un JSON válido", ex);
}
}
}
class MyJson {
public List<Map<String, Object>> array;
}