hibernate 繼承對映關係（ SINGLE_TABLE)

三種繼承對映關係。

 

1，SINGLE_TABLE

 

person student  teacher 在一個表中，student和teacher繼承自person，通過一個DiscriminatorValue的內容來標識該條內容是student還是teacher。

 

package com.bjsxt.hibernate;

import javax.persistence.DiscriminatorColumn;
import javax.persistence.DiscriminatorType;
import javax.persistence.DiscriminatorValue;
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="discriminator", discriminatorType=DiscriminatorType.STRING)
@DiscriminatorValue("person")
public class Person {
    private int id;
    private String name;
   
    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

}

 

package com.bjsxt.hibernate;

import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;

@Entity
@DiscriminatorValue("student")
public class Student extends Person {
   
    private int score;

    public int getScore() {
        return score;
    }

    public void setScore(int score) {
        this.score = score;
    }
   
}

 

package com.bjsxt.hibernate;

import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;

@Entity
@DiscriminatorValue("teacher")
public class Teacher extends Person {
    private String title;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

   
}

 

 

 

測試類：

package com.bjsxt.hibernate;

import java.util.Map;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.tool.hbm2ddl.SchemaExport;
import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;

public class HibernateORMappingTest {
    private static SessionFactory sessionFactory;
   
    @BeforeClass
    public static void beforeClass() {
        new SchemaExport(new AnnotationConfiguration().configure()).create(false, true);
        sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
    }
    @AfterClass
    public static void afterClass() {
        sessionFactory.close();
    }
   
    @Test
    public void testSave() {
        Student s = new Student();
        s.setName("s1");
        s.setScore(80);
        Teacher t = new Teacher();
        t.setName("t1");
        t.setTitle("中級");
       
        Session session = sessionFactory.openSession();
        session.beginTransaction();
        session.save(s);
        session.save(t);
        session.getTransaction().commit();
        session.close();
    }
    @Test
    public void testLoad() {
       
        testSave();
        Session session = sessionFactory.openSession();
        session.beginTransaction();
        Student s = (Student)session.load(Student.class, 1);
        System.out.println(s.getScore());
        Person p = (Person)session.load(Person.class, 2);
        System.out.println(p.getName());
        session.getTransaction().commit();
        session.close();
       
    }
   
    @Test
    public void testSchemaExport() {
        new SchemaExport(new AnnotationConfiguration().configure()).create(false, true);
    }
   
   
    public static void main(String[] args) {
        beforeClass();
    }
}