Object Serialization Using Jackson

We use the Jackson library to serialize an Object such as List, Map, Java object, etc. We can serialize an Object into JSON and put it into a file. In order to serialize an object, we use more than one class and method.

We create the ObjectMapper class to use the writeValue() method. The writeValue() method is used to write data into a JSON file. In order to use the file, we create an instance of the File class.

At the time of serializing Object, three possible exceptions can occur, i.e., JsonGenerationException, JsonParseException, or JsonMappingException. So, we import these three exception classes to handle them.

Let's take an example to understand how serializing is done by using Jackson. In this example, we create a Product class convert it into JSON and store data into a products.json file.

Follow the steps given below to convert Java objects into JSON:

First, we will create a Maven project using Eclipse IDE.
After that, we add Jackson dependency in the pom.xml file to use Jackson for converting Java objects to JSON.
Next, we will create POJO (Product.java), which we want to convert into a JSON file.
Next, we will create a Java class for converting Java objects into JSON.

Product.java

class Product {  
	
	//Creating properties of Product class  
    	private String proId;    
    	private String proName;    
    	private String price;  
    
    	//Getter and Setters  
    	public String getProId() {  
        	return proId;  
    	}  
    	public void setProId(String proId) {  
        	this.proId = proId;  
    	}  
    	public String getName() {  
        	return proName;  
    	}  
    	public void setProName(String proName) {  
        	this.proName = proName;  
    	}  
    	public String getPrice() {  
        	return price;  
    	}  
    	public void setPrice(String price) {  
        	this.price = price;  
    	}  
    	@Override    
    	public String toString() {    
        	// TODO Auto-generated method stub    
        	return "\"Product [ProductId "+ proId + ", ProductName = " + proName + ", ProductPrice = " + price + "]";    
    	}  
}  

ObjectSerialization.java

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Scanner;

import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

// create ObjectSerialization class to convert Java Object into JSON
public class ObjectSerialization {
	
	// main() method start
	public static void main(String args[]){
		
		// create instance of the ObjectSerialization class
		ObjectSerialization obj = new ObjectSerialization();
		
		int size;
		
		Scanner sc1 = new Scanner(System.in);
		System.out.println("Enter total products:");
		size = Integer.parseInt(sc1.nextLine());
		
		
		ArrayList<Product> products = new ArrayList<>();
		
		try {
			
			for(int i = 0; i < size; i++) {
				Product prod = new Product();
				String prodId, prodName, price;
				
				System.out.println("Enter Id of Product"+(i+1));
				prodId = sc1.nextLine();
				prod.setProId(prodId);
				
				System.out.println("Enter Name of Product"+(i+1));
				prodName = sc1.nextLine();
				prod.setProName(prodName);
				
				System.out.println("Enter price of Product"+(i+1));
				price = sc1.nextLine();
				prod.setPrice(price);
				
				products.add(prod);
				
			}
			// call writeJSON() method of the ObjectSerialization class to write List data into products file
			obj.writeJSON(products);
			
			System.out.println("Data is written successfully in product.json file.");

		} catch (JsonParseException e) {
			e.printStackTrace();
		} catch (JsonMappingException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		
		// close scanner class object
		sc1.close();
	}
	
	// create writeJSON() method that will write the list data into products.json file
	public void writeJSON(ArrayList<Product> products) throws JsonGenerationException, JsonMappingException, IOException{
		
		// create an instance of the ObjectMapper class
		ObjectMapper mapper = new ObjectMapper();	
		
		// use writeValue() method to write data into products.json
		mapper.writeValue(new File("C:\\Users\\rastogi ji\\Desktop\\products.json"), products);
	}
}

Output: