一对一关联映射（采用外键+双向）

一对一关联映射（采用外键+双向）

hibernate一对一唯一外键关联映射（双向关联Person<---->IdCard）

一对一唯一外键关联双向，需要在另一端（idcard），添加<one-to-one>标签，指示hibernate如何加载

其关联对象，默认根据主键加载person，外键关联映射中，因为两个实体采用的是person的外键维护的关系，

所以不能指定主键加载person，而要根据person的外键加载，所以采用如下映射方式：

<one-to-one name="person" property-ref="idCard"/>

第一步：编写Person和IdCard实体类：

public class Person {

private int id;

private String name;

private IdCard idCard; 

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;

}

public IdCard getIdCard() {

return idCard;

}

public void setIdCard(IdCard idCard) {

this.idCard = idCard;

}

}

下面是IdCard类：

public class IdCard { private int id; private String cardNo; private Person person; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getCardNo() { return cardNo; } public void setCardNo(String cardNo) { this.cardNo = cardNo; } public Person getPerson() { return person; } public void setPerson(Person person) { this.person = person; } }

第二步：编写实体类的映射文件：

<hibernate-mapping> <class name="com.bjsxt.hibernate.Person" table="t_person"> <id name="id"> <generator class="native"/> </id> <property name="name"/> <many-to-one name="idCard" unique="true"/> </class> </hibernate-mapping>

<hibernate-mapping> <class name="com.bjsxt.hibernate.IdCard" table="t_idcard"> <id name="id"> <generator class="native"/> </id> <property name="cardNo"/> <one-to-one name="person" property-ref="idCard"/>//property-ref="idCard"用于设定要比较的字段，默认的情况下是和Person对象的主键进行比较， //但是我们想让他和Person对象中的idCard字段比较，就需要使用这个标签属性进行设定 </class> </hibernate-mapping>

第三步：编写Hibernate配置文件：

<hibernate-configuration> <session-factory> <property name="hibernate.connection.url">jdbc:mysql://localhost/hibernate_one2one_ufk_1</property> <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property> <property name="hibernate.connection.username">root</property> <property name="hibernate.connection.password">bjsxt</property> <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property> <property name="hibernate.show_sql">true</property> <mapping resource="com/bjsxt/hibernate/IdCard.hbm.xml"/> <mapping resource="com/bjsxt/hibernate/Person.hbm.xml"/> </session-factory> </hibernate-configuration>

第四步：编写测试代码：

public class One2OneTest extends TestCase { public void testSave1() { Session session = null; try { session = HibernateUtils.getSession(); session.beginTransaction(); IdCard idCard = new IdCard(); idCard.setCardNo("88888888888888"); Person person = new Person(); person.setName("菜10"); person.setIdCard(idCard); //不能成功保存，因为IdCard是Transient状态 session.save(person); session.getTransaction().commit(); }catch(Exception e) { e.printStackTrace(); session.getTransaction().rollback(); }finally { HibernateUtils.closeSession(session); } } public void testSave2() { Session session = null; try { session = HibernateUtils.getSession(); session.beginTransaction(); IdCard idCard = new IdCard(); idCard.setCardNo("88888888888888"); session.save(idCard); Person person = new Person(); person.setName("菜10"); person.setIdCard(idCard); session.save(person); session.getTransaction().commit(); }catch(Exception e) { e.printStackTrace(); session.getTransaction().rollback(); }finally { HibernateUtils.closeSession(session); } } public void testLoad1() { Session session = null; try { session = HibernateUtils.getSession(); session.beginTransaction(); Person person = (Person)session.load(Person.class, 2); System.out.println("person.name=" + person.getName()); System.out.println("idCard.cardNo=" + person.getIdCard().getCardNo()); session.getTransaction().commit(); }catch(Exception e) { e.printStackTrace(); session.getTransaction().rollback(); }finally { HibernateUtils.closeSession(session); } } public void testLoad2() { Session session = null; try { session = HibernateUtils.getSession(); session.beginTransaction(); IdCard idCard = (IdCard)session.load(IdCard.class, 1); System.out.println("idcard.cardNo=" + idCard.getCardNo()); System.out.println("idcard.person.name=" + idCard.getPerson().getName()); session.getTransaction().commit(); }catch(Exception e) { e.printStackTrace(); session.getTransaction().rollback(); }finally { HibernateUtils.closeSession(session); } } }