Dyskryminator

 Dyskryminator to typ który grupuje wiersze w tabeli. 

• Stworzenie tabeli w bazie danych 
• Stworzenie klas Entity
• Klasa testująca wyświetlanie danych
• Klasa testująca dodawanie danych

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✅ Stworzenie tabeli w bazie danych 

CREATE DATABASE IF NOT EXISTS `bazatestowa2`;

USE `bazatestowa2`;

CREATE TABLE IF NOT EXISTS animal (

    animal_id INT AUTO_INCREMENT,

    animal_name VARCHAR(40) DEFAULT NULL,

    

    animal_type VARCHAR(40) DEFAULT NULL,

    PRIMARY KEY (owner_id)

) ENGINE=InnoDB;

---

✅ Stworzenie klas Entity 

👉 Entity Animal

package myhibernate.discriminator.entity;

import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.DiscriminatorType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table;

@Entity
@Table(name="animal")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="animal_type", 
discriminatorType = DiscriminatorType.STRING)
public class Animal {
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="animal_id")
private long animal_id;

@Column(name="animal_name")
private String animalName;

public String getAnimalName() {
return animalName;
}

public void setAnimalName(String animalName) {
this.animalName = animalName;
}

@Override
public String toString() {
return "Animal [animal_id=" + animal_id + ", animalName=" + animalName + "]";
}
}

👉 Entity Ptak

package myhibernate.discriminator.entity;

import javax.persistence.DiscriminatorValue;

import javax.persistence.Entity;

@Entity

@DiscriminatorValue("ptak")

public class Ptak extends Animal {

    

}

👉 Entity Ssak

package myhibernate.discriminator.entity;

import javax.persistence.DiscriminatorValue;

import javax.persistence.Entity;

@Entity

@DiscriminatorValue("ssak")

public class Ssak extends Animal {

    

}

---

✅ Klasa testująca wyświetlanie danych

package myhibernate.discriminator;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

import org.hibernate.query.Query;

import myhibernate.discriminator.entity.Animal;

import myhibernate.discriminator.entity.Ptak;

import myhibernate.discriminator.entity.Ssak;

public class DiscriminatorApp {

public static void main(String[] args) {

Configuration conf = new Configuration();

conf.configure("hibernate.cfg.xml");

conf.addAnnotatedClass(Animal.class);

conf.addAnnotatedClass(Ssak.class);

conf.addAnnotatedClass(Ptak.class);

SessionFactory factory = conf.buildSessionFactory();

Session session = factory.getCurrentSession();

session.beginTransaction();

String sql = "select o from Animal o  ";

Query<Animal> query = session.createQuery(sql);

for(Animal animal : query.list()) {

if (animal instanceof Ssak) {

System.out.println("Animal: " + animal);

}

}

session.getTransaction().commit();

factory.close();

}

}

❗ Wynik działania w konsoli: 

---

✅ Klasa testująca dodawanie danych

package myhibernate.discriminator;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

import myhibernate.discriminator.entity.Animal;

import myhibernate.discriminator.entity.Ptak;

import myhibernate.discriminator.entity.Ssak;

public class AddDiscriminatorApp {

public static void main(String[] args) {

Configuration conf = new Configuration();

conf.configure("hibernate.cfg.xml");

conf.addAnnotatedClass(Animal.class);

conf.addAnnotatedClass(Ssak.class);

conf.addAnnotatedClass(Ptak.class);

SessionFactory factory = conf.buildSessionFactory();

Session session = factory.getCurrentSession();

session.beginTransaction();

Ssak ssak = new Ssak();

ssak.setAnimalName("delfin");

session.persist(ssak);

session.getTransaction().commit();

factory.close();

}

}

❗ Wynik działania w konsoli: 

❗Wynik w bazie danych: 

1. tabela animal