一对一的 Hibernate 映射

每个国家都有一个资本。每个首都都有一个国家。

Country.java

package com.entity;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.Table;

@Entity
@Table(name = "countries")
public class Country {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

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

    @Column(name = "national_language")
    private String nationalLanguage;

    @OneToOne(mappedBy = "country")
    private Capital capital;

    //Constructor

    //getters and setters

   }

Capital.java

package com.entity;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
import javax.persistence.Table;

@Entity
@Table(name = "capitals")
public class Capital {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    private String name;

    private long population;

    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "country_id")
    private Country country;

    //Constructor

    //getters and setters

}

HibernateDemo.java

package com.entity;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateDemo {

public static void main(String ar[]) {
    SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
    Session session = sessionFactory.openSession();
    Country india = new Country();
    Capital delhi = new Capital();
    delhi.setName("Delhi");
    delhi.setPopulation(357828394);
    india.setName("India");
    india.setNationalLanguage("Hindi");
    delhi.setCountry(india);
    session.save(delhi);
    session.close();
  }

}