Develop Reference

Concatenate all JSON key-value pairs into a String

I have input:
{
"Id": 200,
"TimeStamp": 1596466800,
"Animal": "cat"
}
I need to concatenate all key-value pairs in one String
I need output:
"Id200Timestamp1596466800Animalcat"

Usually you use a third-party library for parsing JSON. There are several. The below code uses Gson.
Note that the below code is not terribly robust, it assumes that there are no nested elements and that the values are all primitives. That is what you specifically asked for, i.e. specific input and specific output, and I am posting a solution that achieves what you specifically asked for.
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import com.google.gson.JsonPrimitive;
import java.util.Map;
import java.util.Set;
public class GsonTst0 {
public static void main(String[] args) {
String json = "{ \"Id\": 200, \"TimeStamp\": 1596466800, \"Animal\": \"cat\"}";
JsonElement root = JsonParser.parseString(json);
if (root.isJsonObject()) {
JsonObject jsonObj = root.getAsJsonObject();
Set<Map.Entry<String, JsonElement>> entries = jsonObj.entrySet();
StringBuilder sb = new StringBuilder();
for (Map.Entry<String, JsonElement> entry : entries) {
sb.append(entry.getKey());
JsonElement elem = entry.getValue();
JsonPrimitive prim = elem.getAsJsonPrimitive();
if (prim.isNumber()) {
sb.append(prim.getAsBigDecimal());
}
else {
sb.append(prim.getAsString());
}
}
System.out.println(sb);
}
}
}
Running the above code prints the following:
Id200TimeStamp1596466800Animalcat

Reading JSON file using java [duplicate]

This question already has answers here:
How to parse JSON in Java
(36 answers)
Closed 4 months ago.
My issue is that I don't how to find that I have read the first JSON object of the JSON array leave_applicants. This I need to find using java.
{
"leave_applicants":[
{
"applicant_name" : "Jhon",
"supervisor_name" : "Mark",
"org" : "UNDP",
"index_no" : 1,
"leave_details": {
"leave_type" : "annual",
"from" : "12-07-2018",
"to" : "15-07-2018"
}
},
{
"applicant_name" : "Ravi",
"supervisor_name" : "Mark",
"org" : "UNDP",
"index_no" : 2,
"leave_details": {
"leave_type" : "sick_leave_cert",
"from" : "20-07-2018",
"to" : "25-07-2018"
}
}
]
}

Assuming the JSON is in a text file stored on your computer. See the following code and at the end of each iteration of the for loop the end of first JSON object of the JSON array will occur (as you wanted).
import java.io.FileReader;
import java.util.Iterator;
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
public class ReadingJSONFromFile {
#SuppressWarnings("unchecked")
public static void main(String[] args) {
JSONParser parser = new JSONParser();
try {
Object obj = parser.parse(new FileReader(
"Path/To/JSON/File/json_file.txt"));
JSONObject jsonObject = (JSONObject) obj;
JSONArray leaveApplicants = (JSONArray) jsonObject.get("leave_applicants");
for(Object applicants: leaveApplicants) {
JSONObject app = (JSONJObject)applicants;
String name = (String) app.get("applicant_name"); // Get the applicant name
// You can get the other keys of the object similarly and display them as you want
// This will be the end of the first object of the JSON Array
}
} catch (Exception e) {
e.printStackTrace();
}
}
}

Retrieve just one field from JSON string in Java

Is there a way to just one field from the JSON string? My code is as follows:
Object obj = parser.parse(resp);
System.out.println(obj);
JSONArray array = new JSONArray();
array.add(obj);
JSONObject obj2 = (JSONObject)array.get(0); //Getting NPE here
//Object obj3 = obj2.get("data");
System.out.println("Data: " + obj2.get("data"));
//System.out.println("Email: " + obj3.get("email_address"));
I'm using the following libraries
import org.json.simple.JSONObject;
import org.json.simple.JSONArray;
import org.json.simple.parser.ParseException;
import org.json.simple.parser.JSONParser;
From the response string resp, I just need data.email_address. I am unable to find a way to do it.

So if this is your input:
{
"data": {
"email_address": "example#example.com"
}
}
You first will need to make it a JSONObject:
JSONObject object = (JSONObject) new JSONParser().parse(json);
And then you can get data, another JSONObject:
JSONObject data = (JSONObject) object.get("data")
And from your data Object you can get email_address:
String email = data.get("email_address").toString();
If your input is an array of users, like this:
{
"users": [
{
"data": {
"email_address": "example#example.com"
}
},
{
"data": {
"email_address": "exapmle2#example2.com"
}
}
]
}
You can get it the same way:
JSONObject object = (JSONObject) new JSONParser().parse(json);
JSONArray users = (JSONArray) object.get("users");
JSONObject user0 = (JSONObject) users.get(0);
JSONObject user0data = (JSONObject) user0.get("data");
String email = user0data.get("email_address").toString();
First parse the whole JSON into an Object. Then get an array called users, from that array, get index 0. From that Object, get data, and then email_address

The other option is to use jsonpath.
Using the same Json blob as Lorant:
{
"data": {
"email_address": "example#example.com"
}
}
You would use the following expression.
$.data.email_address
Or if it was an array, simply.
$.users.[data].email_address
An online tool can be used to experiment and learn the syntax, but if you know xpath it should be somewhat familiar already.

import org.json.JSONObject;
JSONObject json = new JSONObject(record);
json.getString("fieldName"));

How to convert a string to JSONArray

I am hitting an api and getting a string response. The response is something like this
"["VU","Vanuatu",["Pacific/Efate","(GMT+11:00) Efate"],"VN","Vietnam",["Asia/Saigon","(GMT+07:00) Hanoi"]]"
And i want to convert this string into a json array of below type
[{"id":"VN","name":"Vanuatu","timezones":[{"id":Pacific/Efate,"name":"(GMT+11:00) Efate}]},"id":"VN","name":"Vietnam",[{"id":"Asia/Saigon","name":"(GMT+07:00) Hanoi"}]]
Can someone help

Looking at your String response, I've created a regular expression that will create four groups out of your response.
DEMO
Assuming that your output would come always in groups of four (i.e., id, name and timezones_id, timezones_name), this regular expression, would extract 4 groups out of the input string that you've provided:
Regex:
"([^"]*)",\s*"([^"]*)",\s*\["([^"]*)",\s*"([^"]*)"\]
Matches
Match 1
Full match 1-56 `"VU", "Vanuatu", ["Pacific/Efate", "(GMT+11:00) Efate"]`
Group 1. 2-4 `VU`
Group 2. 8-15 `Vanuatu`
Group 3. 20-33 `Pacific/Efate`
Group 4. 37-54 `(GMT+11:00) Efate`
Match 2
Full match 58-111 `"VN", "Vietnam", ["Asia/Saigon", "(GMT+07:00) Hanoi"]`
Group 1. 59-61 `VN`
Group 2. 65-72 `Vietnam`
Group 3. 77-88 `Asia/Saigon`
Group 4. 92-109 `(GMT+07:00) Hanoi`
 
Now once you've extracted these 4 groups, You can simply add appropriately in ArrayList and List and create JSONArray out of those lists.
The following program is self-explanatory with the inputs and outputs.
Input
["VU","Vanuatu",["Pacific/Efate","(GMT+11:00) Efate"],"VN","Vietnam",["Asia/Saigon","(GMT+07:00) Hanoi"]]
Output
[{"timezones":{"name":"(GMT+11:00) Efate","id":"Pacific/Efate"},"name":"Vanuatu","id":"VU"},{"timezones":{"name":"(GMT+07:00) Hanoi","id":"Asia/Saigon"},"name":"Vietnam","id":"VN"}]
Formatted Output
[{
"id" : "VU",
"name" : "Vanuatu",
"timezones" : {
"name" : "(GMT+11:00) Efate",
"id" : "Pacific/Efate"
}
}, {
"id" : "VN",
"name" : "Vietnam",
"timezones" : {
"name" : "(GMT+07:00) Hanoi",
"id" : "Asia/Saigon"
}
}
]
Code
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.json.JSONArray;
import org.json.JSONException;
public class Test
{
public static void main(String[] args) throws IOException, JSONException {
String serverResponse = "[\"VU\", \"Vanuatu\", [\"Pacific/Efate\", \"(GMT+11:00) Efate\"], \"VN\", \"Vietnam\", [\"Asia/Saigon\", \"(GMT+07:00) Hanoi\"]]";
Map<String, Object> prop, innerProp;
List<Object> arr = new ArrayList<>(), obj;
String pattern = "\"([^\"]*)\",\\s*\"([^\"]*)\",\\s*\\[\"([^\"]*)\",\\s*\"([^\"]*)\"\\]";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(serverResponse);
while (m.find()) {
prop = new HashMap<>();
prop.put("id", m.group(1));
prop.put("name", m.group(2));
innerProp = new HashMap<>();
innerProp.put("id", m.group(3));
innerProp.put("name", m.group(4));
prop.put("timezones", innerProp);
arr.add(prop);
}
JSONArray jsonArray = new JSONArray(arr);
System.out.println(jsonArray.toString());
}
}

An option you have is to first create a JSONArray off of the string, and then read elements 3 by 3 from that array to create your output:
public static void main(String[] args) {
String input = "[\"VU\",\"Vanuatu\",[\"Pacific/Efate\",\"(GMT+11:00) Efate\"],\"VN\",\"Vietnam\",[\"Asia/Saigon\",\"(GMT+07:00) Hanoi\"]]";
JSONArray inputArray = new JSONArray(input);
JSONArray outputArray = new JSONArray();
for (int i = 0; i < inputArray.length(); i += 3) {
JSONObject obj = readCountry(inputArray, i);
outputArray.put(obj);
}
System.out.println(outputArray);
}
private static JSONObject readCountry(JSONArray array, int index) {
JSONObject country = new JSONObject();
country.put("id", array.getString(index));
country.put("name", array.getString(index + 1));
country.put("timezones", readTimeZones(array.getJSONArray(index + 2)));
return country;
}
private static JSONArray readTimeZones(JSONArray array) {
JSONArray timezones = new JSONArray();
JSONObject timezone = new JSONObject();
timezone.put("id", array.getString(0));
timezone.put("name", array.getString(1));
timezones.put(timezone);
return timezones;
}
You may add some error handling to fail gracefully or even recover with best effort if the input doesn't match.

Hi, I need help parse through a JSON file in Java

I am trying to parse through a JSON file using the library JSON simple. The first two string are good. However, when I try to parse through object social I get facebook: null, Pinterest : null, and rss: null. How do I parse through my second object?
Here is my JSON file
{
"blogURL": "www.sheriyBegin",
"twitter": "http://twitter.com/Sherily",
"social": {
"facebook": "http://facebook.com/Sherily",
"pinterest": "https://www.pinterest.com/Sherily/Sherily-articles",
"rss": "http://feeds.feedburner.com/Sherily"
}
}
Here is the code I wrote
package javaugh;
import java.io.FileReader;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
public class JavaUgh {
public static void main(String[] args)throws Exception{
JSONParser parser = new JSONParser();
Object obj = parser.parse(new FileReader("C:\\Users\\HP\\Desktop\\Research\\file2.txt"));
JSONObject jsonObject = (JSONObject) obj;
String blog = (String)jsonObject.get("blogURL");
String twitter = (String)jsonObject.get("twitter");
JSONObject jsonObject2 = (JSONObject) obj;
String face = (String)jsonObject2.get("facebook");
String pin = (String)jsonObject2.get("pinterest");
String rss = (String)jsonObject2.get("rss");
System.out.println("Blog: "+ blog);
System.out.println("Twitter Page : " + twitter);
System.out.println("Socail:");
System.out.println("Facebook Page : " + face);
System.out.println("Pintersect: " + pin);
System.out.println("Rss : " + rss);
}
}
Output:
Blog: www.sheriyBegin
Twitter Page : http://twitter.com/Sherily
Socail:
Facebook Page : null
Pintersect: null
Rss : null

You should obtain the second json object from the first one, not by creating a new reference to the first one.
JSONObject jsonObject2 = (JSONObject) jsonObject.get("social");

JSONObject social = (JSONObject) jsonObject.get("social");
String face = (String)social.get("facebook");
String pin = (String)social.get("pinterest");
String rss = (String)social.get("rss");