@NaturalId in Hibernate

package com.concretepage.persistence;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
import org.hibernate.annotations.NaturalId;
@Entity
@Table(name="car")  
public class Car implements Serializable {
	private static final long serialVersionUID = 1L;
	@Id
	@GeneratedValue
	private int id;
	@NaturalId
	private String vehicleRegNum; 	
	@Column(name="name")
	private String name;
	public Car(String vehicleRegNum,String name){
    	        this.vehicleRegNum=vehicleRegNum;
    	        this.name=name;
        }
	public String getVehicleRegNum() {
		return vehicleRegNum;
	}
	public void setVehicleRegNum(String vehicleRegNum) {
		this.vehicleRegNum = vehicleRegNum;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
} 

<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
  <session-factory>
    <property name="hibernate.connection.url">
    jdbc:mysql://localhost:3306/hibernate</property>
    <property name="hibernate.connection.username">root</property>
    <property name="hibernate.connection.password"></property>
    <property name="hibernate.connection.pool_size">10</property>
    <property name="show_sql">true</property>
    <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
    <property name="hibernate.hbm2ddl.auto">update</property>
    <mapping class="com.concretepage.persistence.Car"/>
   </session-factory>
</hibernate-configuration>
 

package com.concretepage.util;
import java.util.List;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.criterion.Restrictions;
import com.concretepage.persistence.Car;
public class HibernateUtil {
	private static final SessionFactory concreteSessionFactory;
	    static {
	        try {
	            concreteSessionFactory = new AnnotationConfiguration()
	                    .configure().buildSessionFactory();
	        } catch (Throwable ex) {
	            throw new ExceptionInInitializerError(ex);
	        }
	    }
	    public static Session getSession()
	            throws HibernateException {
	        return concreteSessionFactory.openSession();
	    }
	    public static void main(String... args){
	    	Session session=getSession();
	    	session.beginTransaction();
	    	Car c1= new Car("UP65 BN 2343 ","Maruti");
	    	session.persist(c1);
	    	Car c2= new Car("DL60 AN 7845 ","Tata");
	    	session.persist(c2);
	    	session.getTransaction().commit();
	    	List<Car> list=session.createCriteria(Car.class).add(Restrictions.naturalId().set("vehicleRegNum","UP65 BN 2343")).list();
	    	for(Car c:list){
	    		System.out.println(c.getName());
	    	}
	    	session.close();
	    }
	} 

Hibernate: insert into car (name, vehicleRegNum) values (?, ?)
Hibernate: insert into car (name, vehicleRegNum) values (?, ?)
Hibernate: select this_.id as id0_0_, this_.name as name0_0_, this_.vehicleRegNum as vehicleR3_0_0_ from car this_ where (this_.vehicleRegNum=?)
Maruti