create and write JSON

Last Updated On

October 15, 2025

This article shows how to write a JSON using JSON.simple.

This project was formerly JSON.simple 1.x from a Google code project by Yidong, now maintained by Clifton Labs, read this JSON.simple history.

The JSON-simple is a light weight library which is used to process JSON objects. Using this you can read or, write the contents of a JSON document using a Java program.

JSON.simple is available at the Central Maven Repository. Maven users add this to the POM.

<!-- https://mvnrepository.com/artifact/com.github.cliftonlabs/json-simple -->
<dependency>
    <groupId>com.github.cliftonlabs</groupId>
    <artifactId>json-simple</artifactId>
    <version>4.0.1</version>
</dependency>

If the project is Gradle, add the below dependency in build.gradle.

// https://mvnrepository.com/artifact/com.github.cliftonlabs/json-simple
implementation("com.github.cliftonlabs:json-simple:4.0.1")

Write Simple JSON to File using JSON.simple

Below is the sample simple JSON that will be generated. The file will be saved in resources/Payloads as Employee.json.

{ 
    "Working Days":[ 
                             "Monday",
                             "Tuesday",
                             "Wednesday"
                             ],
    "Salary":4500.0,
    "Name":"Vibha"
}

The entire program looks like as shown below:

import com.github.cliftonlabs.json_simple.JsonArray;
import com.github.cliftonlabs.json_simple.JsonObject;
import com.github.cliftonlabs.json_simple.Jsoner;

import java.io.FileWriter;
import java.io.IOException;

public class WriteSimpleJson {
    public static void main(String[] args) {

        // JSON String
        JsonObject jsonObject = new JsonObject();
        jsonObject.put("Name", "Vibha");
        jsonObject.put("Salary", 4500.00);

        // JSON Array
        JsonArray list = new JsonArray();
        list.add("Monday");
        list.add("Tuesday");
        list.add("Wednesday");

        jsonObject.put("Working Days", list);
        System.out.println(Jsoner.serialize(jsonObject));

        try (FileWriter fileWriter = new FileWriter("src/test/resources/Payloads/Employee.json")) {
            Jsoner.serialize(jsonObject, fileWriter);

        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}

The output of the above program is

Explanation

1. Creating a JSON Object

A `JsonObject` named `jsonObject` is created to hold data. Using `put()`, the code adds a “Name” field with the value “Vibha” and a “Salary” field with the value `4500.00` to the JSON object.

JsonObject jsonObject = new JsonObject();
jsonObject.put("Name", "Vibha");
jsonObject.put("Salary", 4500.00);

2. Creating a JSON Array

A `JsonArray` named `list` is created to contain multiple values. The days “Monday”, “Tuesday”, and “Wednesday” are added to the `list`. The JSON array list is added to the jsonObject under the key “Working Days”.

JsonArray list = new JsonArray();
list.add("Monday");
list.add("Tuesday");
list.add("Wednesday");
jsonObject.put("Working Days", list);

3. Writing JSON to a File

A FileWriter is used to open the file src/test/resources/Payloads/Employee.json for writing. The Jsoner.serialize() method serializes the jsonObject and writes it to the file, capturing the constructed JSON structure.

 try (FileWriter fileWriter = new FileWriter("src/test/resources/Payloads/Employee.json")) {
            Jsoner.serialize(jsonObject, fileWriter);

  }

Write Complex JSON to File using JSON.simple

Below is the complex JSON which will be generated.

{
  "Working Days": ["Monday","Tuesday","Wednesday"],
  "Salary":{
    "Bonus":{
      "Quaterly":125.0,
      "Monthly":45.0,
      "Yearly":500.0
    },
    "Fixed":4000.0
  },"Name": {
  "Forename":"Vibha",
  "Surname":"Singh"
 }
}

The entire program looks like as shown below:

import com.github.cliftonlabs.json_simple.JsonArray;
import com.github.cliftonlabs.json_simple.JsonObject;
import com.github.cliftonlabs.json_simple.Jsoner;

import java.io.FileWriter;
import java.io.IOException;

public class WriteComplexJson {

    public static void main(String[] args) {

        JsonObject jsonObject = new JsonObject();

        //Name
        JsonObject name = new JsonObject();
        name.put("Forename", "Vibha");
        name.put("Surname", "Singh");
        jsonObject.put("Name", name);

        //Salary
        JsonObject salary = new JsonObject();
        salary.put("Fixed", 4000.00);

        //Bonus
        JsonObject bonus = new JsonObject();
        bonus.put("Monthly", 45.00);
        bonus.put("Quaterly", 125.00);
        bonus.put("Yearly", 500.00);

        salary.put("Bonus",  bonus);
        jsonObject.put("Salary", salary);

        // JSON Array
        JsonArray list = new JsonArray();
        list.add("Monday");
        list.add("Tuesday");
        list.add("Wednesday");
        jsonObject.put("Working Days", list);

        System.out.println(Jsoner.serialize(jsonObject));

        try (FileWriter fileWriter = new FileWriter("src/test/resources/Payloads/EmployeeDetails.json")) {
            Jsoner.serialize(jsonObject, fileWriter);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}

The output of the above program is

I have saved this file in resources/Payloads as EmployeeDetails.json.

Explanation

1.Creating JSON Objects

Serves as the root JSON object to encapsulate all the other JSON objects and arrays

 JsonObject jsonObject = new JsonObject();

2. Name Object

A JsonObject named name is created. It contains two properties: “Forename” with the value “Vibha” and “Surname” with the value “Singh”. This name object is then added to the root jsonObject under the key “Name”.

JsonObject name = new JsonObject();
name.put("Forename", "Vibha");
name.put("Surname", "Singh");
jsonObject.put("Name", name);

3. Salary Object

A `JsonObject` named `salary` is created with a property “Fixed” representing a fixed salary amount of 4000.00.

//Salary
JsonObject salary = new JsonObject();
salary.put("Fixed", 4000.00);

4. Bonus Object

A `JsonObject` named `bonus` is created. It contains properties for different types of bonuses: “Monthly” (45.00), “Quarterly” (125.00), and “Yearly” (500.00).

The `bonus` object is then added as a property of the `salary` object under the key “Bonus”.

The complete `salary` object, now including the bonus details, is added to the root `jsonObject` under the key “Salary”.

//Bonus
JsonObject bonus = new JsonObject();
bonus.put("Monthly", 45.00);
bonus.put("Quaterly", 125.00);
bonus.put("Yearly", 500.00);

salary.put("Bonus",  bonus);
jsonObject.put("Salary", salary);

5. Creating a JSON Array

A `JsonArray` named `list` is created to represent the working days. The days “Monday”, “Tuesday”, and “Wednesday” are added to this array. This `list` is added to the root `jsonObject` under the key “Working Days”.

// JSON Array
JsonArray list = new JsonArray();
list.add("Monday");
list.add("Tuesday");
list.add("Wednesday");

jsonObject.put("Working Days", list);

6. Serialization of JSON

The entire `jsonObject` is serialized using `Jsoner.serialize()` and printed to the console, which converts the Java JSON structure into a JSON string.

jsonObject.put("Working Days", list);
System.out.println(Jsoner.serialize(jsonObject));

7. Writing the JSON to a File

The `try-with-resources` statement is used to ensure the `FileWriter` is closed automatically. A `FileWriter` writes the serialized JSON object to a file at `src/test/resources/Payloads/EmployeeDetails.json`.

 try (FileWriter fileWriter = new FileWriter("src/test/resources/Payloads/Employee.json")) {
            Jsoner.serialize(jsonObject, fileWriter); }

We are done! Congratulations on making it through this tutorial and hope you found it useful! Happy Learning!!

QA Automation Expert

Automation solutions to build Test Framework

How to create and write JSON with JSON.simple in Java

Write Simple JSON to File using JSON.simple

Write Complex JSON to File using JSON.simple