MyBatis的一对一关系实战

柔光的暖阳◎ 2021-07-25 02:38 446阅读 0赞

**一 新建数据表**

CREATE TABLE tb_card(
    id INT PRIMARY KEY AUTO_INCREMENT,
    CODE VARCHAR(18)
    );
    INSERT INTO tb_card(CODE) VALUES('432801198009191038');
    CREATE TABLE tb_person(
    id INT PRIMARY KEY AUTO_INCREMENT,
    NAME VARCHAR(18),
    sex VARCHAR(18),
    age INT,
    card_id INT UNIQUE,
    FOREIGN KEY (card_id) REFERENCES tb_card(id)
    );
    INSERT INTO tb_person(NAME,sex,age,card_id) VALUES('jack','男',23,1);

**二 领域模型**

1 Card

package org.fkit.domain;
    import java.io.Serializable;
    public class Card implements Serializable {
         
         private static final long serialVersionUID = 1L;
         
         private Integer id;  // 主键id
         private String code; // 身份证编号
         
         public Card() {
               super();
               // TODO Auto-generated constructor stub
         }
         public Integer getId() {
               return id;
         }
         public void setId(Integer id) {
               this.id = id;
         }
         public String getCode() {
               return code;
         }
         public void setCode(String code) {
               this.code = code;
         }
         @Override
         public String toString() {
               return "Card [id=" + id + ", code=" + code + "]";
         }
         
         
    }

2 Person

package org.fkit.domain;
    import java.io.Serializable;
    
    public class Person implements Serializable {
         private static final long serialVersionUID = 1L;
         
         private Integer id;  // 主键id
         private String name; // 姓名
         private String sex;  // 性别
         private Integer age; // 年龄
         
         // 人和身份证是一对一的关系，即一个人只有一个身份证
         private Card card;
         public Person() {
               super();
               // TODO Auto-generated constructor stub
         }
         public Integer getId() {
               return id;
         }
         public void setId(Integer id) {
               this.id = id;
         }
         public String getName() {
               return name;
         }
         public void setName(String name) {
               this.name = name;
         }
         public String getSex() {
               return sex;
         }
         public void setSex(String sex) {
               this.sex = sex;
         }
         public Integer getAge() {
               return age;
         }
         public void setAge(Integer age) {
               this.age = age;
         }
         public Card getCard() {
               return card;
         }
         public void setCard(Card card) {
               this.card = card;
         }
         @Override
         public String toString() {
               return "Person [id=" + id + ", name=" + name + ",  sex=" + sex
                         + ", age=" + age + "]";
         }
    }

**三 会话工厂**

package org.fkit.factory;
    
    import java.io.InputStream;
    
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    public class FKSqlSessionFactory {
        
        private static SqlSessionFactory sqlSessionFactory = null;
        
        // 初始化创建SqlSessionFactory对象
        static{
            try (// 读取mybatis-config.xml文件
                    InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
                ){
                sqlSessionFactory = new SqlSessionFactoryBuilder()
                        .build(is);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        
        // 获取SqlSession对象的静态方法
        public static SqlSession getSqlSession(){
            return sqlSessionFactory.openSession();
        }
    
        // 获取SqlSessionFactory的静态方法
        public static SqlSessionFactory getSqlSessionFactory() {
            return sqlSessionFactory;
        }
    
    }

**四 Mapper**

1 PersonMapper

package org.fkit.mapper;
    import org.fkit.domain.Person;
    public interface PersonMapper {
         
         /**
          * 根据id查询Person
          * 方法名和参数必须和XML文件中的<select.../>元素的id属性和parameterType属性一致
          * @param id
          * @return Person对象
          * */
         Person selectPersonById(Integer id);
         
    }

2 CardMapper.xml

3 PersonMapper.xml

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    
    <mapper namespace="org.fkit.mapper.PersonMapper">
         
      <select id="selectPersonById" parameterType="int"
          resultMap="personMapper">
          SELECT * from tb_person where id = #{id}
      </select>
      
         <resultMap type="org.fkit.domain.Person"  id="personMapper">
               <id property="id" column="id"/>
               <result property="name" column="name"/>
               <result property="sex" column="sex"/>
               <result property="age" column="age"/>
               
               <association property="card" column="card_id"
               select="org.fkit.mapper.CardMapper.selectCardById"
               javaType="org.fkit.domain.Card"/>
         </resultMap>
    </mapper>

**五 配置文件**

driver=com.mysql.jdbc.Driver
    url=jdbc:mysql://127.0.0.1:3306/mybatis
    username=root
    password=123456

log4j.xml

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">  
    <log4j:configuration  xmlns:log4j="http://jakarta.apache.org/log4j/">  
        <appender name="STDOUT"  class="org.apache.log4j.ConsoleAppender">  
            <layout class="org.apache.log4j.PatternLayout">  
                <param name="ConversionPattern" value="%5p [%t] %m%n"  />  
            </layout>  
        </appender>   
         <logger name="org.fkit.mapper">  
            <level value="DEBUG" />  
        </logger>
        <root>  
            <level value="ERROR" />  
            <appender-ref ref="STDOUT" />  
        </root>  
    </log4j:configuration>

mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE configuration
      PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
      "http://mybatis.org/dtd/mybatis-3-config.dtd">
      
    <configuration>
         <properties resource="db.properties"/>
         
         <settings>
               <setting name="logImpl" value="LOG4J"/>
         </settings>
         <environments default="mysql">
         
        <environment id="mysql">
        
          <transactionManager type="JDBC"/>
          
          <dataSource type="POOLED">
            <property name="driver" value="${driver}"/>
            <property name="url" value="${url}"/>
            <property name="username" value="${username}"/>
            <property name="password" value="${password}"/>
          </dataSource>
        </environment>
      </environments>
      
      <mappers>
          <mapper resource="org/fkit/mapper/CardMapper.xml"/>
          <mapper resource="org/fkit/mapper/PersonMapper.xml"/>
      </mappers>
    </configuration>

**六 测试**

package org.fkit.test;
    
    import org.apache.ibatis.session.SqlSession;
    import org.fkit.domain.Person;
    import org.fkit.factory.FKSqlSessionFactory;
    import org.fkit.mapper.PersonMapper;
    
    public class OneToOneTest {
    
        public static void main(String[] args) {
            // 定义SqlSession变量
            SqlSession sqlSession = null;
            try {
                // 创建SqlSession实例
                sqlSession = FKSqlSessionFactory.getSqlSession();
                // 获得mapper接口的代理对象
                PersonMapper pm = sqlSession.getMapper(PersonMapper.class);
                // 直接调用接口的方法，查询id为1的Peson数据
                Person p = pm.selectPersonById(1);
                // 打印Peson对象
                System.out.println(p);
                // 打印Person对象关联的Card对象
                System.out.println(p.getCard());
                // 提交事务
                sqlSession.commit();
            } catch (Exception e) {
                // 回滚事务
                sqlSession.rollback();
                e.printStackTrace();
            }finally {
                // 关闭SqlSession
                if(sqlSession != null)
                    sqlSession.close();
            }
        }
    
    }

**七 测试结果**

DEBUG [main] ==>  Preparing: SELECT * from tb_person where id =  ?
    DEBUG [main] ==> Parameters: 1(Integer)
    DEBUG [main] ====>  Preparing: SELECT * from tb_card where id =  ?
    DEBUG [main] ====> Parameters: 1(Integer)
    DEBUG [main] <====      Total: 1
    DEBUG [main] <==      Total: 1
    Person [id=1, name=jack, sex=男, age=23]
    Card [id=1, code=432801198009191038]