05hibernate_one2one_pk_1(forget)

05hibernate_one2one_pk_1:
package com.bjsxt.hibernate;

import org.hibernate.Session;

import junit.framework.TestCase;

public class One2OneTest extends TestCase {

    public void testSave1() {
        Session session = null;
        try {
            session = HibernateUtils.getSession();
            session.beginTransaction();
            
            IdCard idCard = new IdCard();
            idCard.setCardNo("9999999999999");
            
            Person person = new Person();
            person.setName("七仙女");
            person.setIdCard(idCard);
            
            //不会出现TransientObjectException异常
            //因为一对一主键关联映射中，默认了cascade属性
            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);
        }
    }        
    
}
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hibernate一对一主键关联映射（单向关联Person---->IdCard）

一对一主键关联映射:让两个实体对象的id保持相同，这样可以避免多余的字段被创建

具体映射：
a）主表：IdCard.hbm.xml
<hibernate-mapping>
    <class name="com.bjsxt.hibernate.IdCard" table="t_idcard">
        <id name="id">
        <!--主表，采用自增native-->
            <generator class="native"/>
        </id>
        <property name="cardNo"/>
    </class>
</hibernate-mapping>

b）从表：Person.hbm.xml
    <id name="id">
        <!-- person的主键来源idCard，也就是共享idCard的主键 -->
        <!--从表，采用自增foreign，参考主表IdCare中的主键-->
        <generator class="foreign">
            <param name="property">idCard</param>
        </generator>
    </id>
    <property name="name"/>
    <!-- one-to-one标签的含义，指示hibernate怎么加载它的关联对象，默认根据主键加载，
    constrained="true"，    表明当前主键上存在一个约束，person的主键作为外键参照了idCard    
     -->
    <one-to-one name="idCard" constrained="true"/>

生成的表：
create table t_idcard (id integer not null auto_increment, cardNo varchar(255), primary key (id))

create table t_person (id integer not null, name varchar(255), primary key (id))

alter table t_person add index FK785BED809AC0D5D6 (id), add constraint FK785BED809AC0D5D6 foreign key (id) references t_idcard (id)

mysql> desc t_idcard;
+--------+--------------+------+-----+---------+----------------+
| Field  | Type         | Null | Key | Default | Extra          |
+--------+--------------+------+-----+---------+----------------+
| id     | int(11)      | NO   | PRI | NULL    | auto_increment |
| cardNo | varchar(255) | YES  |     | NULL    |                |
+--------+--------------+------+-----+---------+----------------+
2 rows in set (0.05 sec)

mysql> desc t_person;
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id    | int(11)      | NO   | PRI | NULL    |       |
| name  | varchar(255) | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+
2 rows in set (0.02 sec)    

ＴｅｓｔＬｏａｄ：
Hibernate: insert into t_idcard (cardNo) values (?)
Hibernate: insert into t_person (name, id) values (?, ?)