hibernate学习3之one-to-one单向外键关联
one-to-one关联其实是many-to-one的一种特殊形式。

老规矩。hibernate.cfg.xml先看(没什么特别的吧)

<!DOCTYPE hibernate-configuration PUBLIC"-//Hibernate/Hibernate Configuration DTD 3.0//EN""http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"><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>

下面是2个实体类,一个用户一个卡号

public class IdCard {private int id;private String cardNo;//setter,getter}

public class Person {private int id;private String name;private IdCard idCard; //一个用户一个卡号//setter,getter}

2个映射文件：
IdCard.hbm.xml:

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping><class name="com.bjsxt.hibernate.IdCard" table="t_idcard"><id name="id"><generator name="code"><?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping><class name="com.bjsxt.hibernate.Person" table="t_person"><id name="id"><generator unique="true"/>                <!--                <many-to-one name="idCard" unique="true" cascade="all"/>                --></class></hibernate-mapping>

看上面的配置，其实配置的是many-to-one，只不过one-to-one是many-to-one的特殊情况而已，只要在many-to-one中配置unique="true"，就变成one-to-one关系了。
测试一下：

public void testSave() {Session session = null;try {session = HibernateUtils.getSession();session.beginTransaction();IdCard idCard = new IdCard();idCard.setCardNo("88888888888888");session.save(idCard);//如果设置了级联，这句可以舍去。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);}}