How To Create Array Of Json Objects In Java

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How to Write/create a JSON array using Java?

A Json array is an ordered collection of values that are enclosed in square brackets i.e. it begins with '[' and ends with ']'. The values in the arrays are separated by ',' (comma).

Sample JSON array

{    "books": [ Java, JavaFX, Hbase, Cassandra, WebGL, JOGL] }

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 Java program.

JSON-Simple maven dependency

Following is the maven dependency for the JSON-simple library −

<dependencies>    <dependency>       <groupId>com.googlecode.json-simple</groupId>       <artifactId>json-simple</artifactId>       <version>1.1.1</version>    </dependency> </dependencies>

Paste this with in the <dependencies> </dependencies> tag at the end of your pom.xml file. (before </project> tag)

Example

To create an array in a JSON file using a Java program −

Instantiate the JSONObject class of the json-simple library.

//Creating a JSONObject object JSONObject jsonObject = new JSONObject();

Insert the required key-value pairs using the put() method of the JSONObject class.

jsonObject.put("key", "value");

Create a JSON array by instantiating the JSONArray class and add, elements to the created array using the add() method of the JSONArray class.

JSONArray array = new JSONArray(); array.add("element_1"); array.add("element_2"); array.add("element_3");

After adding all the required elements add the array into the JSON document using the put() method as −

jsonObject.put("contact",array);

Write the created JSON object into a file using the FileWriter class as −

FileWriter file = new FileWriter("E:/json_array_output.json"); file.write(jsonObject.toJSONString()); file.close();

Following Java program creates a JSON object with an array in it and writes it into a file named json_array_output.json.

Example

import java.io.FileWriter; import java.io.IOException; import org.json.simple.JSONArray; import org.json.simple.JSONObject; public class WritingJSONArray {    public static void main(String args[]) {       //Creating a JSONObject object       JSONObject jsonObject = new JSONObject();       //Inserting key-value pairs into the json object       jsonObject.put("ID", "1");       jsonObject.put("First_Name", "Krishna Kasyap");       jsonObject.put("Last_Name", "Bhagavatula");       jsonObject.put("Date_Of_Birth", "1989-09-26");       jsonObject.put("Place_Of_Birth", "Vishakhapatnam");       jsonObject.put("Country", "25000");       //Creating a json array       JSONArray array = new JSONArray();       array.add("e-mail: krishna_kasyap@gmail.com");       array.add("phone: 9848022338");       array.add("city: Hyderabad");       array.add("Area: Madapur");       array.add("State: Telangana");       //Adding array to the json object       jsonObject.put("contact",array);       try {          FileWriter file = new FileWriter("E:/json_array_output.json");          file.write(jsonObject.toJSONString());          file.close();       } catch (IOException e) {          // TODO Auto-generated catch block          e.printStackTrace();       }       System.out.println("JSON file created: "+jsonObject);    } }

Output

JSON file created: { "First_Name":"Krishna Kasyap", "Place_Of_Birth":"Vishakhapatnam", "Last_Name":"Bhagavatula", "contact":[ "e-mail: krishna_kasyap@gmail.com", "phone: 9848022338","city: Hyderabad", "Area: Madapur", "State: Telangana"], "Country":"25000", "ID":"1", "Date_Of_Birth":"1989-09-26"}

If you observe the contents of the JSON file you can see the created data as −