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How to convert a Java object to JSON

Educative Answers Team

JavaScript Object Notation (JSON) is a light-weight data storage format for storing and transmitting data. It is stored in the form of key-value pairs.

There are two main methods used to convert a Java object into a JSON:

  • GSON
  • Jackson API

GSON

The Google GSON​ library is the most popular library used for converting Java objects to JSON.

The code to get a JSON String out of an object is given below.

import com.google.gson.Gson;

public class main
{
    public class Employee {
        private String name;
        private int age;
    }

    public static String convertUsingGson(Employee e)
    {
        Gson gson = new Gson();
        String employeeJson = gson.toJson(e);
        return employeeJson;
    }
}

The GSON dependency library needs to be installed (first) ​in order to declare a Gson object.

Jackson API​

The ObjectMapper API in Jackson is used for data-binding. It comes with several reader/writer methods to perform​ the conversion to/from Java and JSON.

The code to get a JSON String out of an object is given below.

import java.io.File;
import com.fasterxml.jackson.databind.ObjectMapper;

public class main{
   public static void main(String[] args) {
      ObjectMapper mapper = new ObjectMapper();

      Employee emp = createEmployee();
      try {
         // Java objects to JSON string
         String jsonString = mapper.writeValueAsString(emp);
         System.out.println(jsonString);

      } catch (IOException e) {
         e.printStackTrace();
      }

   }

   private static Employee createEmployee() {
      Employee e = new Employee();
      e.setName("Jon");
      e.setAge(25);
      return e;
   }
}

The Jackson dependency library​ needs to be installed (first) ​in order to declare a Jackson/ObjectMapper object.

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java
object
json
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