Как сохранить json в mongodb с помощью spring

Есть пример кода, как можно его переделать под запись json?

 package hello;
import org.springframework.data.annotation.Id;

public class Customer {
    @Id
    public String id;
    public String firstName;
    public String lastName;
    public Customer() {}
    public Customer(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }
    @Override
    public String toString() {
        return String.format(
                "Customer[id=%s, firstName='%s', lastName='%s']",
                id, firstName, lastName);
    }
}

package hello;
import java.util.List;
import org.springframework.data.mongodb.repository.MongoRepository;
public interface CustomerRepository extends MongoRepository<Customer, String> {
    public Customer findByFirstName(String firstName);
    public List<Customer> findByLastName(String lastName);
}
package hello;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class Application implements CommandLineRunner {
    @Autowired
    private CustomerRepository repository;
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
    @Override
    public void run(String... args) throws Exception {
        repository.deleteAll();
        // save a couple of customers
        repository.save(new Customer("Alice", "Smith"));
        repository.save(new Customer("Bob", "Smith"));
        // fetch all customers
        System.out.println("Customers found with findAll():");
        System.out.println("-------------------------------");
        for (Customer customer : repository.findAll()) {
            System.out.println(customer);
        }
        System.out.println();
        // fetch an individual customer
        System.out.println("Customer found with findByFirstName('Alice'):");
        System.out.println("--------------------------------");
        System.out.println(repository.findByFirstName("Alice"));
        System.out.println("Customers found with findByLastName('Smith'):");
        System.out.println("--------------------------------");
        for (Customer customer : repository.findByLastName("Smith")) {
            System.out.println(customer);
        }
    }
}