Hibernate 3.3.1 
Maven 3.0.4 
MySQL 5.5.13 
Myeclipse 8.6.1 

DROP TABLE IF EXISTS `t_card`;
CREATE TABLE `t_card` (
  `cardId` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `cardNumber` char(18) NOT NULL,
  PRIMARY KEY (`cardId`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=gb2312;

INSERT INTO `t_card` VALUES ('1', '440911199008011122');

DROP TABLE IF EXISTS `t_person`;
CREATE TABLE `t_person` (
  `personId` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `personName` varchar(15) NOT NULL,
  `cid` int(10) unsigned NOT NULL,
  PRIMARY KEY (`personId`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=gb2312;

INSERT INTO `t_person` VALUES ('1', 'fancy', '1');

package com.fancy.po;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
import javax.persistence.Table;
/**
 * -----------------------------------------
 * @文件: Person.java
 * @作者: fancy
 * @邮箱: fancyzero@yeah.net
 * @时间: 2012-6-10
 * @描述: 实体类
 * -----------------------------------------
 */
/**
 * @Entity 声明一个类为实体Bean
 * @Table(name = "xx")指定实体类映射的表,如果表名和实体类名一致,可以不指定
 */
@Entity
@Table(name = "t_person")
public class Person {

    private Integer personId;
    private String  personName;
    private Card    card;
    /**
     * @Id 映射主键属性,这里采用uuid的主键生成策略
      * @GeneratedValue —— 注解声明了主键的生成策略。该注解有如下属性
      * strategy 指定生成的策略,默认是GenerationType. AUTO
     * GenerationType.AUTO 主键由程序控制
      * GenerationType.TABLE 使用一个特定的数据库表格来保存主键
      * GenerationType.IDENTITY 主键由数据库自动生成,主要是自动增长类型
      * GenerationType.SEQUENCE 根据底层数据库的序列来生成主键，条件是数据库支持序列
      * generator 指定生成主键使用的生成器
      */
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public Integer getPersonId() {
        return personId;
    }
    /**
     * @OneToOne：一对一关联
      * cascade：级联,它可以有有五个值可选,分别是：
      * CascadeType.PERSIST：级联新建
      * CascadeType.REMOVE : 级联删除
      * CascadeType.REFRESH：级联刷新
      * CascadeType.MERGE  ： 级联更新
      * CascadeType.ALL    ： 以上全部四项
      * @JoinColumn:主表外键字段
      * cid：Person所映射的表中的一个字段
      */
    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "cid")
    public Card getCard() {
        return card;
    }
    public String getPersonName() {
        return personName;
    }
    public void setPersonId(Integer personId) {
        this.personId = personId;
    }
    public void setPersonName(String personName) {
        this.personName = personName;
    }
    public void setCard(Card card) {
        this.card = card;
    }
}

package com.fancy.po;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.Table;
/**
 * -----------------------------------------
 * @文件: Card.java
 * @作者: fancy
 * @邮箱: fancyzero@yeah.net
 * @时间: 2012-6-10
 * @描述: 实体类
 * -----------------------------------------
 */
@Entity
@Table(name = "t_card")
public class Card {

    private Integer cardId;
    private String  cardNumber;
    private Person  person;
    
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public Integer getCardId() {
        return cardId;
    }
    /**
     * @OneToOne：一对一关联
      * mappedBy = "card"：意思是说这里的一对一配置参考了card
     * card又是什么呢?card是Person类中的getCard(),注意不是Person类中的
      * card属性,Person类中的OneToOne配置就是在getCard()方法上面配的.
     * 如果Person类中的getCard()方法改成getIdCard(),其他不变的话,
     * 这里就要写成：mappedBy = "idCard"
     */
    @OneToOne(mappedBy = "card")
    public Person getPerson() {
        return person;
    }
    public String getCardNumber() {
        return cardNumber;
    }
    public void setCardId(Integer cardId) {
        this.cardId = cardId;
    }
    public void setCardNumber(String cardNumber) {
        this.cardNumber = cardNumber;
    }
    public void setPerson(Person person) {
        this.person = person;
    }
}

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.fancy</groupId>
  <artifactId>hibernate-annotation-on-to-one-example</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>
  <name>hibernate-annotation-on-to-one-example</name>
  <url>http://maven.apache.org</url>
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>
  
  <dependencies>
    <!-- hibernate jar -->
    <dependency>
      <groupId>org.hibernate</groupId>
      <artifactId>hibernate-entitymanager</artifactId>
      <version>3.3.1.ga</version>
    </dependency>
    <!-- hibernate annotation jar -->
    <dependency>
      <groupId>org.hibernate</groupId>
      <artifactId>hibernate-annotations</artifactId>
      <version>3.3.1.GA</version>
    </dependency>
    <!-- mysql -->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.17</version>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
  
</project>

package com.fancy.test;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.cfg.Configuration;
import com.fancy.po.Card;
import com.fancy.po.Person;
/**
 * -----------------------------------------
 * @文件: Test.java
 * @作者: fancy
 * @邮箱: fancyzero@yeah.net
 * @时间: 2012-6-10
 * @描述: 测试类
 * -----------------------------------------
 */
public class Test {

    public static void main(String[] args) {
        
        //读取hibernate配置,默认读取classpath下的hibernate.cfg.xml
        Configuration conf = new AnnotationConfiguration();    
        //构建session工厂
         SessionFactory sessionFactory = conf.configure().buildSessionFactory();
        //打开session
        Session session = sessionFactory.openSession();
        //开始事务
         session.beginTransaction();
        // * * * * * * * * * * * * * * * * * * * * * * * * * * * *
        //test1(session);    //测试 1
        //test2(session);    //测试 2
        test3(session);      //测试 3
        // * * * * * * * * * * * * * * * * * * * * * * * * * * * *
        //提交事务
         session.getTransaction().commit();
        //关闭session工厂
         sessionFactory.close();
       //关闭session
       session.close();
    }
    /**
     * 数据库初始值：
      * personName：fancy
     * cardNumber：440911199008011122
     */
    //测试方法1
    public static void test1(Session session){
        Person person = (Person)session.get(Person.class, 1); //发出Person和Card的select语句
         Card card = person.getCard();
        System.out.println(person.getPersonName());
        System.out.println(card.getCardNumber());
        person.setPersonName("fancy");            //与初始值一致
         card.setCardNumber("440911199008011122");//与初始值一致
         session.save(person);    //不发出sql语句
       //session.save(card);     //不发出sql语句
    }
    //测试方法2
    public static void test2(Session session){
        Person person = (Person)session.get(Person.class, 1); //发出Person和Card的select语句
         Card card = person.getCard();
        System.out.println(person.getPersonName());
        System.out.println(card.getCardNumber());
        person.setPersonName("fancyzero");        //与初始值不一致
         card.setCardNumber("440911199008011122");//与初始值一致
         session.save(person);    //发出Person的update语句,数据库中personName被修改,不发出Card的update语句
       //session.save(card);     //发出Person的update语句,数据库中personName被修改,不发出Card的update语句
    }
    //测试方法3
    public static void test3(Session session){
        Person person = (Person)session.get(Person.class, 1); //发出Person和Card的select语句
         Card card = person.getCard();
        System.out.println(person.getPersonName());
        System.out.println(card.getCardNumber());
        person.setPersonName("fancy");           //与初始值不一致
         card.setCardNumber("440911199008080808");//与初始值不一致
         session.save(person);    //同时发出Person和Card的update语句,数据库中的数据相应被修改
       //session.save(card);     //同时发出Person和Card的update语句,数据库中的数据相应被修改
    }
}