8.3 Hibernate：一对多单向关联（unidirectional）

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复用 8.2 Hibernate：多对一单向关联（unidirectional）应用场景。

1 重新定义映射类：
1.1 表 person 的映射类定义：

package hibernate;import java.util.ArrayList;
import java.util.Date;
import java.util.List;import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.ForeignKey;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;@Entity
@Table(name = "person")
public class Person {@Id@GeneratedValue(strategy = GenerationType.IDENTITY)@Column(name = "id")private int id;@Column(name = "name")private String name;@Column(name = "birth")private Date birth;@OneToMany@JoinColumn(name = "owner_id",foreignKey = @ForeignKey(name = "FK_PHONE"))private List<Phone> phones = new ArrayList<>();public Person() {}public Person(String name, Date birth) {this.name = name;this.birth = birth;}// 省略 Getters 和 Setters ...}

1.2 表 phone 的映射类定义：

package hibernate;import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;@Entity
@Table(name = "phone")
public class Phone {@Id@GeneratedValue(strategy = GenerationType.IDENTITY)@Column(name = "id")private int id;@Column(name = "imei")private String imei;@Column(name = "number")private String number;public Phone() {}public Phone(String imei, String number) {this.imei = imei;this.number = number;}// 省略 Getters 和 Setters ...}

2 测试
2.1 新增

@Test
public void testInsert() {Configuration configuration = new Configuration().configure("hibernate.cfg.xml");SessionFactory sessionFactory = configuration.buildSessionFactory();Session session = sessionFactory.openSession();Transaction transaction = session.beginTransaction();Person person = new Person("Jack", new Date());Phone phone1 = new Phone("866661234567890", "18012345678");session.save(phone1);person.getPhones().add(phone1);Phone phone2 = new Phone("866660987654321", "18087654321");session.save(phone2);person.getPhones().add(phone2);session.save(person);transaction.commit();session.close();sessionFactory.close();
}

注意：
(1) 新增一对多关系数据时，默认需要分别保存“一”方数据和“多”方数据，且“多”方数据可以单独保存，但是保存“一”方数据依赖于保存“多”方数据；
(2) 如果想实现级联新增，则需要设置 @OneToMany 的 cascade 属性。

2.2 删除
2.2.1 单独删除“多”方数据成功

@Test
public void test() {Configuration configuration = new Configuration().configure("hibernate.cfg.xml");SessionFactory sessionFactory = configuration.buildSessionFactory();Session session = sessionFactory.openSession();Transaction transaction = session.beginTransaction();List<Phone> phones = session.createQuery(" FROM Phone").list();for (Phone phone : phones) {session.delete(phone);}transaction.commit();session.close();sessionFactory.close();
}

2.2.2 单独删除“一”方数据成功，因为没有将 phone 中外键 owner_id 设置为 NOT NULL

@Test
public void test() {Configuration configuration = new Configuration().configure("hibernate.cfg.xml");SessionFactory sessionFactory = configuration.buildSessionFactory();Session session = sessionFactory.openSession();Transaction transaction = session.beginTransaction();Person person = (Person) session.createQuery(" FROM Person").list().get(0);session.delete(person);transaction.commit();session.close();sessionFactory.close();
}

如果想实现级联删除，则需要设置 @OneToMany 的 cascade 属性。

2.3 更新

@Test
public void test() {Configuration configuration = new Configuration().configure("hibernate.cfg.xml");SessionFactory sessionFactory = configuration.buildSessionFactory();Session session = sessionFactory.openSession();Transaction transaction = session.beginTransaction();Person person = (Person) session.createQuery(" FROM Person").list().get(0);person.setName("Tommy");person.setBirth(new Date());String imei = "86000000000000";String number = "1300000000";for (int i = 0; i < person.getPhones().size(); i++) {person.getPhones().get(i).setImei(imei + (i + 1));person.getPhones().get(i).setNumber(number + (i + 1));}session.save(person);transaction.commit();session.close();sessionFactory.close();
}

运行测试，person 及其关联的 phone 记录已经级联更新了。

2.4 查询

@Test
public void test() {Configuration configuration = new Configuration().configure("hibernate.cfg.xml");SessionFactory sessionFactory = configuration.buildSessionFactory();Session session = sessionFactory.openSession();Transaction transaction = session.beginTransaction();Person person = (Person) session.createQuery(" FROM Person").list().get(0);System.out.println("Person Name : " + person.getName());System.out.println("Person Birth : " + person.getBirth());for (int i = 0; i < person.getPhones().size(); i++) {System.out.println("---------- Person's Phone " + (i + 1) + " ----------");System.out.println("Phone IMEI : " + person.getPhones().get(i).getImei());System.out.println("Phone Number : " + person.getPhones().get(i).getNumber());}transaction.commit();session.close();sessionFactory.close();
}

运行测试，打印结果：

Person Name : Jack
Person Birth : 2017-07-09 22:27:00.0
......
---------- Person's Phone 1 ----------
Phone IMEI : 866661234567890
Phone Number : 18012345678
---------- Person's Phone 2 ----------
Phone IMEI : 866660987654321
Phone Number : 18087654321

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