18 - Implementing Inheritance - Single Table Strategy

Single table inheritance strategy.

@DiscriminatorColumn(

                                name="VEHICLE_TYPE",

                                discriminatorType=DiscriminatorType.STRING

)

It changes dtype to vehicle_type in table

HibernateTest.java

package org.yash.hibernate;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

import org.yash.dto.FourWheeler;

import org.yash.dto.TwoWheeler;

import org.yash.dto.Vehicle;

public class HibernateTest {

      public static void main(String args[]) {

            Vehicle vehicle = new Vehicle();

            vehicle.setVehicleName("Car");

            TwoWheeler bike = new TwoWheeler();

            bike.setVehicleName("Bike");

            bike.setSteeringHandle("Bike Steering Handle");

            FourWheeler car = new FourWheeler();

            car.setVehicleName("Porsche");

            car.setSteeringWheel("Porsche Steering Wheel");

            SessionFactory sessionFactory = new Configuration().configure()

                        .buildSessionFactory();

            Session session = sessionFactory.openSession();

            /* It is used to save all the objects and to define single unit of work */

            session.beginTransaction();

            session.save(vehicle);

            session.save(bike);

            session.save(car);

            session.getTransaction().commit();

            session.close();

      }

}

Vehicle.java

package org.yash.dto;

import javax.persistence.DiscriminatorColumn;

import javax.persistence.DiscriminatorType;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.Inheritance;

import javax.persistence.InheritanceType;

@Entity

@Inheritance(strategy=InheritanceType.SINGLE_TABLE)

@DiscriminatorColumn(

            name="VEHICLE_TYPE",

            discriminatorType=DiscriminatorType.STRING

)

public class Vehicle {

      @Id @GeneratedValue

      private int vehicleId;

      private String vehicleName;

      public int getVehicleId() {

            return vehicleId;

      }

      public void setVehicleId(int vehicleId) {

            this.vehicleId = vehicleId;

      }

      public String getVehicleName() {

            return vehicleName;

      }

      public void setVehicleName(String vehicleName) {

            this.vehicleName = vehicleName;

      }

}

TwoWheeler.java

package org.yash.dto;

import javax.persistence.DiscriminatorValue;

import javax.persistence.Entity;

@Entity

@DiscriminatorValue("Bike")

public class TwoWheeler extends Vehicle {

      private String SteeringHandle;

      public void setSteeringHandle(String steeringHandle) {

            SteeringHandle = steeringHandle;

      }

      public String getSteeringHandle() {

            return SteeringHandle;

      }    

     

}

FourWheeler.java

package org.yash.dto;

import javax.persistence.DiscriminatorValue;

import javax.persistence.Entity;

@Entity

@DiscriminatorValue("Car")

public class FourWheeler extends Vehicle {

            private String steeringWheel;

            public void setSteeringWheel(String steeringWheel) {

                  this.steeringWheel = steeringWheel;

            }

            public String getSteeringWheel() {

                  return steeringWheel;

            }

     

}