Mybatis---一对一关联映射

最常见的一对一关联映射案例就是每个人只有对应的唯一身份证

一、项目准备

jdbc包，mybatis包，junit5(eclipse自带)

二、设计数据库

两个表tb_idcard和tb_person,其中card_id是tb_person的外键，并插入部分数据。

三、贴代码

db.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1/mybatisTest2	
jdbc.username=root
jdbc.password=1234

log4j.properties

# Global logging configuration
log4j.rootLogger=ERROR, stdout
# MyBatis logging configuration...
log4j.logger.com.ssm=DEBUG
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

IdCard.java

package pojo;


public class IdCard {
    private Integer id;
    private String code;
    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 "IdCard [id=" + id + ", code=" + code + "]";
    }
}

Person.java

package pojo;

public class Person {
    private Integer id;
    private String name;
    private IdCard card;  //个人关联的证件
	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 IdCard getCard() {
		return card;
	}
	public void setCard(IdCard card) {
		this.card = card;
	}
	@Override
	public String toString() {
		return "Person [id=" + id + ", name=" + name + ", card=" + card + "]";
	}
   
}

IdCardMapper.xml

	
	
		select*from tb_idCard where id = #{id}
	

PersonMapper.xml

    
    
        SELECT * from tb_person where id=#{id}
    
    
        
        
        
        
    

MybatisTest.java

package test;


import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import pojo.Person;
import utils.Utils;

public class MybatisTest {
   
    @Test
    public void findPersonByIdTest() {
        // 1、通过工具类生成SqlSession对象
        SqlSession session = Utils.getSession();
        // 2.使用MyBatis嵌套查询的方式查询id为1的人的信息
        Person person = session.selectOne("pojo"
                + ".PersonMapper.findPersonById", 1);
        // 3、输出查询结果信息
        System.out.println(person);
        // 4、关闭SqlSession
        session.close();
    }

    
}

utils.java

package utils;

import java.io.Reader;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
/**
 * 工具类
 */
public class Utils {
    private static SqlSessionFactory sqlSessionFactory = null;
    // 初始化SqlSessionFactory对象
    static {
        try {
            // 使用MyBatis提供的Resources类加载MyBatis的配置文件
            Reader reader =
                    Resources.getResourceAsReader("mybatis-config.xml");
            // 构建SqlSessionFactory工厂
            sqlSessionFactory =
                    new SqlSessionFactoryBuilder().build(reader);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    // 获取SqlSession对象的静态方法
    public static SqlSession getSession() {
        return sqlSessionFactory.openSession();
    }
}

Mybatis-config.xml

四、测试

点开MybatisTest.java,找到findPersonByIdTest()，右键run as---junit test

运行截图：

至于上面的报错就不知道是什么原因了