Hibernate_映射_关联关系_一对一映射2_基于外键的方式

单向关联:
  单向一对多
  单向多对一
  单向多对多
  单向一对一(只能做从有外键方到无外键方的单向关联)

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 导入包 -->
<hibernate-mapping package="cn.itcast.i_hbm_oneToOne">
  <!-- 类名 -->
  <class name="Person" table="t_person">
    <id name="id" type="integer" column="id">
      <generator class="native" />
    </id>
    <property name="name" type="string" column="name" />

    <!-- idCard属性,IdCard类型 
      表达的是本类与IdCard的一对一。 
      采用外键一对一映射方式,本方无外键方 
      property-ref属性:
        写的是对方映射中外键列对应的属性名
    -->
    <one-to-one name="idCard" class="IdCard" property-ref="person" />
  </class>
</hibernate-mapping>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 导入包 -->
<hibernate-mapping package="cn.itcast.i_hbm_oneToOne">
  <!-- 类名 -->
  <class name="IdCard" table="t_idcard">
    <id name="id" type="integer" column="id">
      <generator class="native" />
    </id>
    <property name="number" type="string" column="number" />
    
    <!-- person属性,Person类型 
      表达的是本类与Person的一对一。
      采用外键一对一映射方式,本方有外键方
    -->
    <many-to-one name="person" class="Person" column="personId" unique="true" ></many-to-one>
  </class>
</hibernate-mapping>

package cn.itcast.i_hbm_oneToOne;

/**
 * 公民实体类
 * 
 * @author 风清杨
 * @version V1.0
 */
public class Person {
  private Integer id;// 主键id
  private String name;// 姓名
  private IdCard idCard;// 关联的身份证

  public Integer getId() {
    return id;
  }

  public void setId(Integer id) {
    this.id = id;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public IdCard getIdCard() {
    return idCard;
  }

  public void setIdCard(IdCard idCard) {
    this.idCard = idCard;
  }

  @Override
  public String toString() {
    return "IdCard [id=" + id + ", name=" + name + "]";
  }
}

package cn.itcast.i_hbm_oneToOne;

/**
 * 身份证 实体类
 * 
 * @author 风清杨
 * @version V1.0
 */
public class IdCard {
  private Integer id;// 主键
  private String number;// 身份证编号
  private Person person;// 关联的公民对象

  public Integer getId() {
    return id;
  }

  public void setId(Integer id) {
    this.id = id;
  }

  public String getNumber() {
    return number;
  }

  public void setNumber(String number) {
    this.number = number;
  }

  public Person getPerson() {
    return person;
  }

  public void setPerson(Person person) {
    this.person = person;
  }

  @Override
  public String toString() {
    return "IdCard [id=" + id + ", number=" + number + "]";
  }

}

package cn.itcast.i_hbm_oneToOne;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.junit.Test;

/**
 * 应用程序操作类
 * 
 * @author 风清杨
 * @version V1.0
 * 
 */
public class App {
  private static SessionFactory sessionFactory = new Configuration()//
      .configure()//
      .addClass(Person.class)//
      .addClass(IdCard.class)//
      .buildSessionFactory();

  // 保存,有关联关系
  @Test
  public void testSave() throws Exception {
    Session session = sessionFactory.openSession();
    Transaction tx = null;
    try {
      tx = session.beginTransaction();
      // ------------------------------------

      // 新建对象
      Person person = new Person();
      person.setName("张三");

      IdCard idCard = new IdCard();
      idCard.setNumber("10000001X");

      // 关联起来
      person.setIdCard(idCard);
      idCard.setPerson(person);

      // 保存
      session.save(person);
      session.save(idCard);
      // ------------------------------------
      tx.commit();
    } catch (RuntimeException e) {
      tx.rollback();
      throw e;
    } finally {
      session.close();
    }
  }

  // 获取,可以获取到关联的对方
  @Test
  public void testGet() throws Exception {
    Session session = sessionFactory.openSession();
    Transaction tx = null;
    try {
      tx = session.beginTransaction();
      // ------------------------------------

      // 获取一方数据,并显示另一方信息
      // Person person = (Person) session.get(Person.class, 1);
      // System.out.println(person);
      // System.out.println(person.getIdCard());

      IdCard idCard = (IdCard) session.get(IdCard.class, 1);
      System.out.println(idCard);
      System.out.println(idCard.getPerson());
      // ------------------------------------
      tx.commit();
    } catch (RuntimeException e) {
      tx.rollback();
      throw e;
    } finally {
      session.close();
    }
  }

  // 解除关联关系：一对一中,只能有外键可以维护关联关系
  @Test
  public void testRemoveRelation() throws Exception {
    Session session = sessionFactory.openSession();
    Transaction tx = null;
    try {
      tx = session.beginTransaction();
      // ------------------------------------

      // 从有外键方解除关系,可以。
      // IdCard idCard = (IdCard) session.get(IdCard.class, 1);
      // idCard.setPerson(null);

      // 从无外键方解除关系,不可以。
      Person person = (Person) session.get(Person.class, 1);
      person.setIdCard(null);

      // ------------------------------------
      tx.commit();
    } catch (RuntimeException e) {
      tx.rollback();
      throw e;
    } finally {
      session.close();
    }
  }

  // 删除对象,对关联对象的影响
  @Test
  public void testDelete() throws Exception {
    Session session = sessionFactory.openSession();
    Transaction tx = null;
    try {
      tx = session.beginTransaction();
      // ------------------------------------

      // a,如果没有关联的对方：
      // b,如果有关联的对方且可以维护关联关系(有外键方),它就会先删除关联关系,再删除自已。
      // c,如果有关联的对方且不能维护关联关系(无外键方),所以会直接执行删除自已,就会有异常。
      IdCard idCard = (IdCard) session.get(IdCard.class, 1);
      session.delete(idCard);

      // Person person = (Person) session.get(Person.class,1);
      // session.delete(person);

      // ------------------------------------
      tx.commit();
    } catch (RuntimeException e) {
      tx.rollback();
      throw e;
    } finally {
      session.close();
    }
  }
}