zoukankan html css js c++ java

Java进阶知识34 mybatis+Oracle 单向一对一关联之CRUD操作【xml 版】

本文知识点（目录）：

      1、导读
          1.1、技术概述
          1.2、本文使用的jar包、项目结构图
      2、本文所有代码（xml版）
          2.1、数据库脚本（oracle.sql）
          2.2、mybatis.xml 核心配置文件
          2.3、MyBatisUtils 工具类（用于连接数据库）
          2.4、实体类（Student、Card ）以及对应的xxxxxMapper.xml 配置文件
          2.5、DAO层（Student类对应的接口及接口实现类、Card类对应的接口及接口实现类）
          2.6、测试类（StudentDaoTest）及测试结果

1、导读

1.1、技术概述

a.本文使用的是Oracle+mybatis框架，单向一对一关联，以Student为主；（数据表之间的关系：card是主表，student是从表）

b.实现了CURD等操作：新增、修改、查询全部、多条件查询、根据id查询、删除、批量删除。

c.本文只测试/演示DAO层与数据库之间的连接以及数据的CRUD操作

d.本项目的使用环境：MyEclipse10.7 + JDK1.8 + Oracle11g + mybatis3.1.1

1.2、本文使用的jar包、项目结构图

2、本文所有代码（xml版）

2.1、数据库脚本（oracle.sql）

 1 create table student( -- 从表
 2     id number(5) primary key,
 3     name varchar2(20),
 4     sex number(1),
 5     age number(3),
 6     telphone varchar2(11),
 7     card_id number(5),
 8     constraint student_card_fk foreign key(card_id) references card(id)
 9 );
10 /*
11  手动插入外键的方法：alter table student add constraint student_card_fk foreign key(card_id) references card(id);
12 */
13 
14 create table card( -- 主表
15     id number(6) primary key,
16     card_number varchar2(20),
17     description varchar2(50)
18 );
19 
20 -- 创建序列
21 create sequence student_seq
22 minvalue 1    --最小值
23 maxvalue 99999    -- 最大值
24 increment by 1    --从1开始计数
25 start with 1    --每次加1
26 nocycle        --一直累加，不循环
27 nocache;    --不建缓冲区。
28 
29 create sequence card_seq
30 minvalue 1    
31 maxvalue 99999    
32 increment by 1 
33 start with 1    
34 nocycle        
35 nocache;    
36 
37 -- 创建触发器
38 create or replace trigger student_tg
39   before insert on student for each row 
40     begin
41       select student_seq.Nextval into:new.id from dual;
42   end;
43 
44 create or replace trigger card_tg
45   before insert on card for each row 
46     begin
47       select card_seq.Nextval into:new.id from dual;
48   end;
49 
50 -- 插入数据
51 insert into card(card_number,description) values('123456789','市民卡-学生');
52 insert into card(card_number,description) values('888888888','市民卡-上班族');
53 insert into card(card_number,description) values('987654321','市民卡-老年人');
54 insert into student(name,sex,age,telphone,card_id) values('zhangsan',0,18,'13859501266',1);

2.2、mybatis.xml 核心配置文件

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
 3 "http://mybatis.org/dtd/mybatis-3-config.dtd">
 4 <configuration>
 5     <environments default="development">
 6         <environment id="development">
 7             <transactionManager type="JDBC" />
 8             <dataSource type="POOLED">
 9                 <property name="driver" value="oracle.jdbc.driver.OracleDriver" />
10                 <property name="url" value="jdbc:oracle:thin:@localhost:1521:shoreid" />
11                 <property name="username" value="zhangsan" />
12                 <property name="password" value="123456" />
13             </dataSource>
14         </environment>
15     </environments>
16 
17     <mappers><!-- 5、通过SqlSession对象读取XXXXXMapper.xml映射文件中的对应操作id，从而获取sql语句； -->
18         <mapper resource="com/shore/o2o/entity/StudentMapper.xml"/>
19         <mapper resource="com/shore/o2o/entity/CardMapper.xml"/>
20     </mappers>
21 </configuration>

2.3、MyBatisUtils 工具类（用于连接数据库）

 1 package com.shore.common.utils;
 2 
 3 import java.io.Reader;
 4 
 5 import org.apache.ibatis.io.Resources;
 6 import org.apache.ibatis.session.SqlSession;
 7 import org.apache.ibatis.session.SqlSessionFactory;
 8 import org.apache.ibatis.session.SqlSessionFactoryBuilder;
 9 
10 /**
11  * @author DSHORE/2020-3-12
12  *
13  */
14 public class MyBatisUtils {
15     private static ThreadLocal<SqlSession> threadLocal = new ThreadLocal<SqlSession>();
16     private static SqlSessionFactory sqlSessionFactory;
17     
18     static{
19         try {
20             //1、读取配置
21             Reader reader = Resources.getResourceAsReader("mybatis.xml");
22             //2、创建SqlSessionFactory
23             sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
24         } catch (Exception e) {
25             e.fillInStackTrace();
26             throw new RuntimeException(e);
27         }
28     }
29     
30     private MyBatisUtils() { }
31     
32     //3、获取SqlSession
33     public static SqlSession getSqlSession(){
34         SqlSession sqlSession = threadLocal.get();
35         if (sqlSession == null) {//如果上面获取不到SQLSession，将通过下面的方式来获取
36             sqlSession = sqlSessionFactory.openSession();
37         }
38         return sqlSession;
39     }
40     
41     //7、关闭SqlSession
42     public static void closeSqlSession() {
43         SqlSession sqlSession = threadLocal.get();
44         if (sqlSession != null) {
45             sqlSession.close();
46             threadLocal.remove();
47         }
48     }
49 }

2.4、实体类（Student、Card ）以及对应的xxxxxMapper.xml 配置文件

Student.java 实体类

 1 package com.shore.o2o.entity;
 2 
 3 /**
 4  * @author DSHORE/2020-3-12
 5  *  mybatis：单向一对一关联，以Student为主
 6  */
 7 public class Student {
 8     private Integer id;
 9     private String name;
10     private Integer sex;
11     private Integer age;
12     private String telphone;
13     private Card card;
14 
15     //此处省略了Setters和Getters方法
16 
17     @Override
18     public String toString() {
19         return "Student [id=" + id + ", name=" + name + ", sex=" + sex
20                 + ", age=" + age + ", telphone=" + telphone + ", card=" + card
21                 + "]";
22     }
23 }

StudentMapper.xml 配置文件

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 3 "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 4 
 5 <mapper namespace="studentNameSpace">
 6     <resultMap id="studentResultMap" type="com.shore.o2o.entity.Student">
 7         <id property="id" column="id"/> <!-- property和 column不能省略-->
 8         <result property="name" column="name"/>
 9         <result property="sex" column="sex"/>
10         <result property="age" column="age"/>
11         <result property="telphone" column="telphone"/>
12         <!-- 单向一对一关联，以Student为主 -->
13         <association property="card" column="card_id" resultMap="cardNameSpace.cardResultMap"/>
14     </resultMap>
15     
16     <!--======================= 新增 ============================= -->
17     <insert id="addStudent" parameterType="com.shore.o2o.entity.Student">
18         insert into student(name,sex,age,telphone,card_id)
19          values(#{name,jdbcType=VARCHAR},#{sex,jdbcType=NUMERIC},#{age,jdbcType=NUMERIC},#{telphone,jdbcType=VARCHAR},#{card.id,jdbcType=NUMERIC})
20     </insert>
21     
22     <!--======================= 修改 ============================= -->
23     <update id="updateStudent" parameterType="com.shore.o2o.entity.Student">
24         update student 
25         set 
26             <if test="name != null">
27                 name=#{name,jdbcType=VARCHAR},
28             </if>
29             <if test="sex != null">
30                 sex=#{sex,jdbcType=NUMERIC},
31             </if>
32             <if test="age != null">
33                 age=#{age,jdbcType=NUMERIC},
34             </if>
35             <if test="telphone != null">
36                 telphone=#{telphone,jdbcType=VARCHAR},
37             </if>
38             <if test="card.id != null">
39                 card_id=#{card.id,jdbcType=NUMERIC} 
40             </if>
41         where id=#{id,jdbcType=NUMERIC}
42     </update>
43     
44     <!--===================== 根据id查询 =========================== -->
45     <select id="findById" parameterType="int" resultMap="studentResultMap">
46         select s.*,c.* 
47          from student s,card c
48         where s.card_id = c.id and s.id = #{id}
49     </select>
50     
51     <!--===================== 多条件查询=========================== -->
52     <!-- resultMap和 parameterType的区别：
53         如果用resultMap="studentResultMap"；则，student表以及关联表card中的数据都查询出来。
54         如果用parameterType="com.shore.o2o.entity.Student"；则，查询结果只有student表的数据，card表为null。
55     -->
56     <select id="MulticonditionalQuery" parameterType="map" resultMap="studentResultMap">
57         select s.*,c.* from student s,card c
58         <where>
59             <if test="name != null">
60                 or name = #{name}
61             </if>
62             <if test="telphone != null">
63                 or telphone = #{telphone}
64             </if>
65         </where>
66     </select>
67     
68     <!--=======================查询全部============================= -->
69     <select id="selectAll" resultMap="studentResultMap">
70         select s.*,c.* 
71         from student s,card c 
72         where s.card_id = c.id
73     </select>
74     
75     <!--======================== 删除 ============================== -->
76     <delete id="deleteByStudentId" parameterType="int">
77         delete from student where id=#{id}
78     </delete>
79     
80     <!--======================= 批量删除 ============================ -->
81     <delete id="batchDeleteById">
82         delete from student where id in 
83         <foreach item="ids" collection="list" open="(" separator="," close=")">
84             #{ids}
85         </foreach>
86     </delete>
87 </mapper>

Card.java 实体类

 1 package com.shore.o2o.entity;
 2 
 3 /**
 4  * @author DSHORE/2020-3-12
 5  * mybatis：单向一对一关联，以Student为主
 6  */
 7 public class Card {
 8     private Integer id;
 9     private String number;
10     private String description;
11 
12     //此处省略了Setters和Getters方法
13 
14     @Override
15     public String toString() {
16         return "Card [id=" + id + ", number=" + number + ", description="
17                 + description + "]";
18     }
19 }

CardMapper.xml 配置文件

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 3 "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 4 
 5 <mapper namespace="cardNameSpace">
 6     <resultMap id="cardResultMap" type="com.shore.o2o.entity.Card">
 7         <id property="id" column="id" /> <!-- property和 column不能省略 -->
 8         <result property="number" column="card_number" />
 9         <result property="description" column="description" />
10     </resultMap>
11 
12     <!--======================= 新增 ============================= -->
13     <insert id="addCard" parameterType="com.shore.o2o.entity.Card">
14         <!-- 返回当前，刚刚插入的数据的id，用于student表的外键card_id -->
15         <selectKey order="AFTER" keyProperty="id" resultType="java.lang.Integer">
16             <!-- 这里的id是自增长的（序列+触发器），具体请看oracle.sql中的数据表脚本 -->
17             select max(id) as id from card
18             <!-- select card_seq.Nextval as id from dual -->
19         </selectKey>
20         insert into card(card_number,description)
21         values(#{number,jdbcType=VARCHAR},#{description,jdbcType=VARCHAR})
22     </insert>
23 
24     <!--===================== 根据id查询 =========================== -->
25     <select id="findById" parameterType="int" resultMap="cardResultMap">
26         select * from card where id = #{id,jdbcType=NUMERIC}
27     </select>
28 </mapper>

2.5、DAO层（Student类对应的接口及接口实现类、Card类对应的接口及接口实现类）

IStudentDao.java（接口类）

 1 package com.shore.o2o.dao;
 2 
 3 import java.util.List;
 4 
 5 import com.shore.o2o.entity.Student;
 6 
 7 /**
 8  * @author DSHORE/2020-3-12
 9  *
10  */
11 public interface IStudentDao {
12     public int addStudent(Student student);//新增
13     
14     public int updateStudent(Student student);//修改
15     
16     public Student findByStudentId(int id);//根据id查询
17     
18     public List<Student> MulticonditionalQuery(String name, String telphone);//多条件查询
19     
20     public List<Student> listAll();//查询所有
21     
22     public int deleteStudent(int id);//删除
23     
24     public int batchDeleteById(List<Integer> ids);//批量删除
25 }

StudentDao.java（接口类 IStudentDao 的实现类）

  1 package com.shore.o2o.dao.impl;
  2 
  3 import java.util.ArrayList;
  4 import java.util.HashMap;
  5 import java.util.List;
  6 import java.util.Map;
  7 
  8 import org.apache.ibatis.session.SqlSession;
  9 
 10 import com.shore.common.utils.MyBatisUtils;
 11 import com.shore.o2o.dao.IStudentDao;
 12 import com.shore.o2o.entity.Student;
 13 
 14 /**
 15  * @author DSHORE/2020-3-12
 16  *
 17  */
 18 public class StudentDao implements IStudentDao {
 19     
 20     SqlSession sqlSession = null;
 21 
 22     @Override //新增
 23     public int addStudent(Student student) {
 24         sqlSession = MyBatisUtils.getSqlSession();
 25         try {
 26             return sqlSession.insert("studentNameSpace.addStudent", student);
 27         } catch (Exception e) {
 28             sqlSession.rollback();//如果出现异常,则,事务回滚
 29             System.out.println(e.getMessage());//打印异常信息
 30         } finally {
 31             sqlSession.commit();//提交事务
 32             MyBatisUtils.closeSqlSession();//关闭SqlSession
 33         }
 34         return 0;
 35     }
 36 
 37     @Override //修改
 38     public int updateStudent(Student student) {
 39         sqlSession = MyBatisUtils.getSqlSession();
 40         try {
 41             return sqlSession.insert("studentNameSpace.updateStudent", student);
 42         } catch (Exception e) {
 43             sqlSession.rollback();//如果出现异常,则,事务回滚
 44             System.out.println(e.getMessage());//打印异常信息
 45         } finally {
 46             sqlSession.commit();//提交事务
 47             MyBatisUtils.closeSqlSession();//关闭SqlSession
 48         }
 49         return 0;
 50     }
 51 
 52     @Override //根据id查询
 53     public Student findByStudentId(int id) {
 54         List<Student> students = new ArrayList<Student>();
 55         Student student = null;
 56         sqlSession = MyBatisUtils.getSqlSession();
 57         try {
 58             students = sqlSession.selectList("studentNameSpace.findById",id);
 59             if (students!=null&&students.size()>0) {
 60                 student = students.get(0);
 61             }
 62         } catch (Exception e) {
 63             System.out.println(e.getMessage());//打印错误/异常信息
 64         } finally {
 65             MyBatisUtils.closeSqlSession();//关闭SqlSession
 66         }    
 67         return student;
 68     }
 69 
 70     @Override //多条件查询
 71     public List<Student> MulticonditionalQuery(String name, String telphone) {
 72         List<Student> students = new ArrayList<Student>();
 73         sqlSession = MyBatisUtils.getSqlSession();
 74         try {
 75             Map<String, String> map = new HashMap<String, String>();
 76             map.put("name", name);
 77             map.put("telphone", telphone);
 78             students = sqlSession.selectList("studentNameSpace.MulticonditionalQuery", map);
 79         } catch (Exception e) {
 80             System.out.println("error:" + e.getMessage());
 81         } finally {
 82             MyBatisUtils.closeSqlSession();
 83         }
 84         return students;
 85     }
 86 
 87     @Override //查询所有
 88     public List<Student> listAll() {
 89         List<Student> students = new ArrayList<Student>();
 90         sqlSession = MyBatisUtils.getSqlSession();
 91         try {
 92             students = sqlSession.selectList("studentNameSpace.selectAll");
 93         } catch (Exception e) {
 94             System.out.println("error:" + e.getMessage());
 95         } finally {
 96             MyBatisUtils.closeSqlSession();
 97         }
 98         return students;
 99     }
100 
101     @Override //删除（只删除student表的消息，不删除关联表card的消息）
102     public int deleteStudent(int id) {
103         sqlSession = MyBatisUtils.getSqlSession();
104         try {
105             return sqlSession.delete("studentNameSpace.deleteByStudentId", id);
106         } catch (Exception e) {
107             sqlSession.rollback();
108             System.out.println(e.getMessage());
109         } finally {
110             sqlSession.commit();
111             MyBatisUtils.closeSqlSession();
112         }
113         return 0;
114     }
115 
116     @Override //批量删除
117     public int batchDeleteById(List<Integer> ids) {
118         sqlSession = MyBatisUtils.getSqlSession();
119         try {
120             return sqlSession.delete("studentNameSpace.batchDeleteById", ids);
121         } catch (Exception e) {
122             sqlSession.rollback();
123             System.out.println("error:"+e.getMessage());
124         } finally {
125             sqlSession.commit();
126             MyBatisUtils.closeSqlSession();
127         }
128         return 0;
129     }
130 }

ICardDao.java（接口类）

 1 package com.shore.o2o.dao;
 2 
 3 import com.shore.o2o.entity.Card;
 4 
 5 /**
 6  * @author DSHORE/2020-3-13
 7  *
 8  */
 9 public interface ICardDao {
10     public int addCard(Card card);//新增
11     
12     public Card findByCardId(int id);//根据id查询
13 }

CardDao.java（接口类 ICardDao 的实现类）

 1 package com.shore.o2o.dao.impl;
 2 
 3 import java.util.ArrayList;
 4 import java.util.List;
 5 
 6 import org.apache.ibatis.session.SqlSession;
 7 
 8 import com.shore.common.utils.MyBatisUtils;
 9 import com.shore.o2o.dao.ICardDao;
10 import com.shore.o2o.entity.Card;
11 
12 /**
13  * @author DSHORE/2020-3-12
14  *
15  */
16 public class CardDao implements ICardDao{
17     SqlSession sqlSession = null;
18     
19     @Override //新增
20     public int addCard(Card card) {
21         sqlSession = MyBatisUtils.getSqlSession();
22         try {
23             return sqlSession.insert("cardNameSpace.addCard", card);
24         } catch (Exception e) {
25             sqlSession.rollback();//如果出现异常,则,事务回滚
26             System.out.println(e.getMessage());//打印异常信息
27         } finally {
28             sqlSession.commit();//提交事务
29             MyBatisUtils.closeSqlSession();//关闭SqlSession
30         }
31         return 0;
32     }
33     
34     @Override //根据id查询
35     public Card findByCardId(int id) {
36         List<Card> cards = new ArrayList<Card>();
37         Card card = null;
38         sqlSession = MyBatisUtils.getSqlSession();
39         try {
40             cards = sqlSession.selectList("cardNameSpace.findById",id);
41             if (cards != null && cards.size() > 0) {
42                 card = cards.get(0);
43             }
44         } catch (Exception e) {
45             System.out.println(e.getMessage());
46         } finally {
47             MyBatisUtils.closeSqlSession();
48         }    
49         return card;
50     }
51 }

2.6、测试类（StudentDaoTest）及测试结果

  1 package test.student;
  2 
  3 import java.util.ArrayList;
  4 import java.util.List;
  5 
  6 import org.junit.Test;
  7 
  8 import com.shore.o2o.dao.IStudentDao;
  9 import com.shore.o2o.dao.impl.CardDao;
 10 import com.shore.o2o.dao.impl.StudentDao;
 11 import com.shore.o2o.entity.Card;
 12 import com.shore.o2o.entity.Student;
 13 
 14 /**
 15  * @author DSHORE/2020-3-12
 16  *
 17  */
 18 public class StudentDaoTest {
 19     IStudentDao studentDao = new StudentDao();
 20     CardDao cardDao = new CardDao();
 21     
 22     @Test //新增
 23     public void testAdd() {
 24         Student student = new Student();
 25         student.setName("zhangsan");
 26         student.setSex(1);//0代表男，1代表女
 27         student.setAge(27);
 28         student.setTelphone("1234567890");
 29         
 30         //使用新建的方式
 31         /*Card card = new Card();
 32         card.setNumber("6666666666");
 33         card.setDescription("市民卡-学生");
 34         System.out.println(cardDao.addCard(card));//返回值：1 */        
 35         //使用数据表card中 已经有的数据
 36         Card card = cardDao.findByCardId(2);
 37         
 38         student.setCard(card);
 39         System.out.println(studentDao.addStudent(student));//返回值：1     说明插入数据成功；如果是0，说明插入失败
 40     }
 41     
 42     @Test //修改
 43     public void testUpdate() {
 44         Student student = new Student();
 45         student.setId(7);
 46         student.setName("李四");
 47         student.setSex(1);
 48         student.setAge(20);
 49         student.setTelphone("18795901366");
 50         
 51         Card card = cardDao.findByCardId(2);
 52         student.setCard(card);
 53         
 54         System.out.println(studentDao.updateStudent(student));//返回值：1
 55     }
 56     
 57     @Test //根据id查询
 58     public void testFindById() {
 59      //返回值：Student[id=1,name=zhangsan,sex=0,age=26,telphone=1234567890,card=Card[id=1,number=6666666666,description=市民卡-学生卡]]
 60         System.out.println(studentDao.findByStudentId(1));
 61     }
 62     
 63     @Test //多条件查询
 64     public void testFindByCondition() {
 65         List<Student> students = studentDao.MulticonditionalQuery(null, "12345678900");
 66         System.out.println(students.size());//返回值：1   说明查到一条记录
 67         
 68         List<Student> students2 = studentDao.MulticonditionalQuery("DSHORE","18795901366");
 69         for (Student stu : students2) {
 70             System.out.println(stu);
 71             /* 返回值：
 72              * Student[id=2,name=DSHORE,sex=0,age=26,telphone=13859501266,card=Card[id=2,number=1681688888,description=市民卡-普通]]
 73              * Student[id=7,name=李四,sex=1,age=20,telphone=18795901366,card=Card[id=7,number=1234567890,description=市民卡-学生]]
 74              * Student[id=29,name=赵六,sex=1,age=26,telphone=18795901366,card=Card[id=29,number=1681688888,description=市民卡-普通]]
 75              * */
 76         }
 77     }
 78     
 79     @Test //查询全部
 80     public void testListAll() {
 81         List<Student> students = studentDao.listAll();
 82         if (students == null) {
 83             System.out.println("students is null。");
 84         } else {
 85             //System.out.println(students.get(0));
 86             for (Student stu : students) {
 87                 System.out.println(stu);//返回值很多，就不列出来了
 88             }
 89         }
 90     }
 91     
 92     @Test //删除 （只删除student表的消息，不删除关联表card的消息）
 93     public void testDelete() {
 94         System.out.println(studentDao.deleteStudent(32));//返回值：1    说明删除数据成功
 95     }
 96     
 97     @Test // 批量删除 （只删除student表的消息，不删除关联表card的消息）
 98     public void testBatchDelete() {
 99         List<Integer> ids = new ArrayList<Integer>();
100         ids.add(5);
101         ids.add(6);
102         ids.add(7);
103         System.out.println(studentDao.batchDeleteById(ids));//返回值：3    说明批量删除数据成功
104     }
105 }

到此已完结！有任何问题，可留言。

mybatis单向一对一关联映射：https://www.cnblogs.com/dshore123/p/12489304.html
mybatis单向一对多关联映射：https://www.cnblogs.com/dshore123/p/12493450.html
mybatis单向多对多关联映射：https://www.cnblogs.com/dshore123/p/12526016.html

原创作者：DSHORE

作者主页：http://www.cnblogs.com/dshore123/

原文出自：https://www.cnblogs.com/dshore123/p/12489304.html

查看全文

相关阅读:
【Lintcode】112.Remove Duplicates from Sorted List
【Lintcode】087.Remove Node in Binary Search Tree
【Lintcode】011.Search Range in Binary Search Tree
【Lintcode】095.Validate Binary Search Tree
【Lintcode】069.Binary Tree Level Order Traversal
【Lintcode】088.Lowest Common Ancestor
【Lintcode】094.Binary Tree Maximum Path Sum
【算法总结】二叉树
 库（静态库和动态库）
从尾到头打印链表

原文地址：https://www.cnblogs.com/dshore123/p/12489304.html

Java进阶知识34 mybatis+Oracle 单向一对一关联 之CRUD操作【xml 版】

1、导读

2、本文所有代码（xml版）

Java进阶知识34 mybatis+Oracle 单向一对一关联之CRUD操作【xml 版】