How To Convert Object To JsonObject In Java?

In Java, a JSON object is a collection of key-value pairs. The keys are always strings, while the values can be strings, numbers, boolean values, or arrays. They help to store and exchange data in a standardized format.

Example:

{“name”: Nancy,” age”:31,” email”:”[email protected]”,”isdoctor” : true}

The JSON object in the example has three properties: name, age, email, and boolean. The values of the name and email properties are strings, the age property has a number value, and the isdoctor property has a boolean value.

In software development, the conversion of objects to JSON objects is a common task. Java provides built-in libraries and third-party libraries such as Jackson and Gson that provide more advanced features for working with JSON data.

In this blog, we will explore how to convert objects to JSON objects in Java using both built-in and third-party libraries.

Why Is There A Need To Convert An Object To A JSON Object In Java?

Converting objects to Json objects is necessary in Java programming for several reasons.

1. Data Interchange: This ensures easy data transmission over the internet.

2. Storing Data: JSON is also used for storing data in files or databases.

3. Front-End Development: JSON is used in frameworks like Angular and React. By converting an object to a JSON object, you can pass data between the server and client in a format that these frameworks can easily parse.

Three Methods For Converting Object To JsonObject In Java:

There are several ways to convert an object to Jsonobject in Java:

1. Using Jackson ObjectMapper
2. Using Gson’s TypeToken
3. Using JSONObject class

A Thorough Explanation Of Each Strategy About How To Convert Object To Json Object In Java:

1. Using Jackson ObjectMapper Method To change Object To Json Object In Java:

Jackson is a popular Java library that can be used for converting objects to JSON format. We can use the ObjectMapper class to convert objects to JSON format.For using the Jackson library,we need to add a dependency.

Sample Code:

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class Main {
    public static void main(String[] args) {
        // Create an object
        Person person = new Person("Harry", 50);

        // Convert the object to a JSON object
        ObjectMapper objectMapper = new ObjectMapper();
        String json = objectMapper.writeValueAsString(person);

        // Print the JSON object
        System.out.println(json);
    }

    // Define the Person class
    static class Person {
        private String name;
        private int age;

        // Constructor
        public Person(String name, int age) {
            this.name = name;
            this.age = age;
        }

        // Getters
        public String getName() {
            return name;
        }

        public int getAge() {
            return age;
        }
    }
}

Output:

{"name":"Harry","age":50}

Code Explanation:

1. The code starts by importing the necessary packages: com.fasterxml.jackson.core.JsonProcessingException and com.fasterxml.jackson.databind.ObjectMapper.
2. Next, a Person class is defined with a constructor that takes a name and age, as well as getter methods for each property.
3. In the main method, a new Person object is created with the name “Harry” and age 50.
4. An ObjectMapper object is created, which is responsible for converting Java objects to JSON.
5. The writeValueAsString method of the ObjectMapper class is used to convert the Person object to a JSON string representation of the object.
6. The resulting JSON object is printed to the console using System.out.println.

2.Change Object To Json Object Using Gson’s TypeToken Method:

Gson is another popular Java library for converting objects to JSON format. Before using it, you would need to add its dependency to your project. Once that is done, you can utilize the Gson class to perform the conversion.

Sample Code:

import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;

public class Main {
    public static void main(String[] args) {
        // Create an object of Person class
        Person person = new Person("Harry", 50);

        // Convert the Person object to a JSON object
        Gson gson = new Gson(); // Create a Gson object
        JsonElement jsonElement = gson.toJsonTree(person); // Convert the Person object to a JsonElement object
        JsonObject jsonObject = jsonElement.getAsJsonObject(); // Convert the JsonElement object to a JsonObject object

        // Print the JSON object to the console
        System.out.println(jsonObject);
    }

    static class Person {
        private String name;
        private int age;

        public Person(String name, int age) {
            this.name = name;
            this.age = age;
        }

        public String getName() {
            return name;
        }

        public int getAge() {
            return age;
        }
    }
}

Output:

{
  "name":"Harry",
  "Age":50
}

Code Explanation:

1. The Main class contains a main() method that creates an object of the Person class and converts it to a JSON object using the Gson library.
2. The Person class is a simple class that has a name and an age property.
3. In the main() method, a new Person object is created with the name “Harry” and age 50.
4. A new Gson object is created, which is used to convert the Person object to a JSON object.
5. The toJsonTree() method of the Gson object is called with the Person object as an argument. This method converts the Person object to a JsonElement object.
6. The getAsJsonObject() method of the JsonElement object is called to convert the JsonElement object to a JsonObject object.
7. The resulting JsonObject object is printed to the console using the println() method of System.out.
8. The output of the program will be a JSON object that represents the Person object created in the main() method.

3.Using JSONObject To Convert Object To Json Object

In case you prefer not to utilize any external library, you have the option to use the JSONObject class available in the Java Standard Library for converting objects to JSON format.

Sample Code:

import org.json.JSONObject;
public class Main {
    public static void main(String[] args) {

        Person person = new Person("Harry", 50);

        // Convert the object to a JSON object
        JSONObject jsonObject = new JSONObject();
        jsonObject.put("name", person.getName());
        jsonObject.put("age", person.getAge());

        // Print the JSON object
        System.out.println(jsonObject);
    }

    static class Person {
        private String name;
        private int age;

        public Person(String name, int age) {
            this.name = name;
            this.age = age;
        }

        public String getName() {
            return name;
        }

        public int getAge() {
            return age;
        }
    }
}

Output:

{"name":"Harry","age":50}

Code Explanation:

1. The code defines a Person class with a name and an age attribute.
2. A Person object is created with the name “Harry” and age 50.
3. A new JSONObject is created.
4. The name and age properties of the Person object are added to the JSONObject using the put method.
5. The JSONObject is printed to the console using System.out.println().

Best Of The Three Methods

For numerous reasons, Jackson ObjectMapper is regarded as the finest java method to turn an object into a Jsonobject.

1. High Performance: Jackson has a reputation for being highly performant, making it suitable for use in applications that require fast serialization and deserialization of large, complex objects.

2. Advanced Features: Jackson offers a range of advanced features, that can help simplify the process of converting complex objects to JSON format. Moreover, Jackson’s API is flexible and customizable, making it possible to fine-tune the serialization and deserialization process to meet specific project requirements.

3. Integration: Jackson is designed to integrate seamlessly with other Java libraries and frameworks, making it a popular choice for use in large-scale projects.

4. Documentation and Support: Jackson has extensive documentation, tutorials, and community support, which can be helpful for developers who are new to the library.

Sample Problems For Converting Object To Json Object In Java:

Sample Problem 1:

Can you write a Java method that uses the Jackson library to convert a Student object to a JSON object? The method should take a Student object as input and return a String object that represents the same data in JSON format.

Solution:

1. Import the Jackson library in your Java project.
2. Create a Java method that takes a Student object as input.
3. Create an instance of the ObjectMapper class from the Jackson library.
4. Use the ObjectMapper instance to convert the Student object to a JSON string.
5. Return the JSON string as a String object.

 Code:

import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonConverter {
    
    // method to convert Student object to JSON string
    public static String convertToJson(Student student) {
        ObjectMapper mapper = new ObjectMapper(); // create ObjectMapper instance
        String json = "";
        try {
            json = mapper.writeValueAsString(student); // use ObjectMapper to convert Student to JSON
        } catch (Exception e) {
            e.printStackTrace();
        }
        return json; // return JSON string
    }

    public static void main(String[] args) {
        Student student = new Student("Alice", 18, 3.5); // create a new Student object
        String json = JsonConverter.convertToJson(student); // call convertToJson method to convert Student object to JSON string
        System.out.println(json); // print JSON string
    }
}

// Student class with name, age, and grade fields
class Student {
    private String name;
    private int age;
    private double grade;

    // constructor to initialize Student object with name, age, and grade
    public Student(String name, int age, double grade) {
        this.name = name;
        this.age = age;
        this.grade = grade;
    }

    // getter and setter methods for name field
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    // getter and setter methods for age field
    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    // getter and setter methods for grade field
    public double getGrade() {
        return grade;
    }

    public void setGrade(double grade) {
        this.grade = grade;
    }
}

Output:

{"name":"Alice","age":18,"grade":3.5}

Sample Problem 2:

You are working on a project for a car rental company, and you need to implement a method that converts a Car object to a JSON object using the Gson library. The method should take a Car object as input and return a String object that represents the same data in JSON format.

The Car class has the following attributes:

make (string)

model (string)

year (integer)

dailyRentalRate (double)

Write a Java method that uses the Gson library to convert a Car object to a JSON object.

Solution:

1. Import the Gson library in your Java code.

2. Define a Car class with the following attributes: make, model, year, and dailyRentalRate.

3. Define a method that takes a Car object as input and returns a String object that represents the same data in JSON format.

4. Create a Gson object to use for serialization.

5. Serialize the Car object to a JSON string using the toJson() method of the Gson object.

6. Return the JSON string from the method.

 Code:

// Import the Gson library
import com.google.gson.Gson;

// Define a class for converting a Car object to JSON format
public class JsonConverter {
    
    // Define a static method that takes a Car object as input and returns its JSON representation as a String
    public static String convertToJson(Car car) {
        
        // Create a new Gson object
        Gson gson = new Gson();
        
        // Use the Gson object to convert the Car object to JSON format and store it as a String
        String json = gson.toJson(car);
        
        // Return the JSON string
        return json;
    }

    // Define a main method for testing the JSON conversion
    public static void main(String[] args) {
        
        // Create a new Car object with some sample data
        Car car = new Car("Audi", "A3", 2023, 45.88);
        
        // Convert the Car object to JSON format using the convertToJson method
        String json = JsonConverter.convertToJson(car);
        
        // Print the resulting JSON string
        System.out.println(json);
    }
}

// Define a Car class with the necessary attributes
class Car {
    
    // Define private instance variables for the Car class
    private String make;
    private String model;
    private int year;
    private double dailyRentalRate;

    // Define a constructor for the Car class that takes in the necessary attributes
    public Car(String make, String model, int year, double dailyRentalRate) {
        this.make = make;
        this.model = model;
        this.year = year;
        this.dailyRentalRate = dailyRentalRate;
    }

    // Define getter and setter methods for the Car class
    public String getMake() {
        return make;
    }

    public void setMake(String make) {
        this.make = make;
    }

    public String getModel() {
        return model;
    }

    public void setModel(String model) {
        this.model = model;
    }

    public int getYear() {
        return year;
    }

    public void setYear(int year) {
        this.year = year;
    }

    public double getDailyRentalRate() {
        return dailyRentalRate;
    }

    public void setDailyRentalRate(double dailyRentalRate) {
        this.dailyRentalRate = dailyRentalRate;
    }
}

Output:

{"make":"Audi","model":"A3","year":2023,"dailyRentalRate":45.88}

Sample Problem 3:

Create a Java method that converts a Book object to a JSON object using the JSONObject class provided by Java. The Book object has four attributes: title (String), author (String), publicationYear (int), and price (double).

Solution:

1. Import the JSONObject class from the org.json package.

2. Define a method that takes a Book object as a parameter and returns a JSONObject.

3. Create a new JSONObject instance.

4. Use the put method of the JSONObject class to add the values of the Book object to the JSON object, using the keys “title”, “author”, “publicationYear”, and “price”.

5. Return the resulting JSONObject.

6. Use the created method in the main method or other parts of the code where the conversion is needed.

 Code:

import org.json.JSONObject;

public class JsonConverter {
    public static JSONObject convertToJson(Book book) {
        // Create a new JSONObject
        JSONObject json = new JSONObject();
        
        // Add the book data to the JSONObject
        json.put("title", book.getTitle());
        json.put("author", book.getAuthor());
        json.put("publicationYear", book.getPublicationYear());
        json.put("price", book.getPrice());
        
        // Return the JSONObject
        return json;
    }

    public static void main(String[] args) {
        // Create a new Book object
        Book book = new Book("Listen to Your Heart: The London Adventure", "Ruskin Bond",2022, 8.88);
        
        // Convert the Book object to a JSONObject
        JSONObject json = JsonConverter.convertToJson(book);
        
        // Print the JSONObject to the console
        System.out.println(json);
    }
}

class Book {
    private String title;
    private String author;
    private int publicationYear;
    private double price;

    public Book(String title, String author, int publicationYear, double price) {
        this.title = title;
        this.author = author;
        this.publicationYear = publicationYear;
        this.price = price;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public int getPublicationYear() {
        return publicationYear;
    }

    public void setPublicationYear(int publicationYear) {
        this.publicationYear = publicationYear;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }
}

Output:

{
"title": "Listen to Your Heart: The London Adventure",
"author": "Ruskin Bond",
"publicationYear":2022,
"price": 8.88
}

Conclusion:

In this blog post, we learned how to convert objects to Json object in java. Converting an object value to a json object can be achieved using several methods like Jackson ObjectMapper library,Gson’s TypeToken and JSONObject.

However, after examining the advantages of each approach, it’s clear that Jackson is the best option to use.But, the other methods can be useful in certain situations. When choosing a method, consider which one is the most appropriate for your use case.