mybatis 一对一级联 一对多

Posted 2020-10-12

一：一对一   用association

一   建表

   course 课程与score 课程成绩表是一对一关系

 course课程表

 

score课程成绩表

连接数据库dbconf.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"></properties>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <!-- 配置数据库连接信息 -->
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
<mappers>
    <!--<mapper resource="StfMapper.xml"/>-->
    <!--<mapper resource="KcMapper.xml"/>-->
    <mapper resource="StudMapper.xml"/>
    <mapper resource="ScoreMapper.xml"/>
    <mapper resource="CourseMapper.xml"/>
</mappers>
</configuration>
写一个db.properties文件
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/myba
jdbc.username=root
jdbc.password=×××

 

 

 

 二 使用mybatis插件自动生成相对应表的配置文件

   CourseMapper.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="com.ygy.mapper.CourseMapper" >
  <resultMap id="course" type="com.ygy.model.Course" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Fri Oct 27 12:25:54 CST 2017.
    -->
    <id column="coid" property="coid" jdbcType="INTEGER" />
    <result column="coname" property="coname" jdbcType="VARCHAR" />
  </resultMap>
 <select id="selectcou" resultMap="course" parameterType="int">
   SELECT myba.course.* from myba.course WHERE coid=#{coid}
 </select>
</mapper>

CourseMapper接口
*CourseMapper.xml是对接口的实现 所以 select 的id与接口中方法名相同

package com.ygy.mapper;

import com.ygy.model.Course;
import com.ygy.model.CourseExample;
import java.util.List;
import org.apache.ibatis.annotations.Param;

public interface CourseMapper {
    public Course selectcou(int id);
}

ScoreMapper.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="com.ygy.mapper.ScoreMapper" >
  <resultMap id="score" type="com.ygy.model.Score" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Fri Oct 27 12:25:54 CST 2017.
    -->
    <id column="scid" property="scid" jdbcType="INTEGER" />
    <result column="scsid" property="scsid" jdbcType="INTEGER" />
    <result column="sckcid" property="sckcid" jdbcType="INTEGER" />
    <result column="mark" property="mark" jdbcType="VARCHAR" />
    <association property="course" column="sckcid" select="com.ygy.mapper.CourseMapper.selectcou"/>
  </resultMap>
  <select id="selectscore" parameterType="int" resultMap="score">
    select myba.score.* from myba.score WHERE myba.score.scsid=#{id}
  </select>
</mapper>

ScoreMapper接口

package com.ygy.mapper;

import com.ygy.model.Score;
import com.ygy.model.ScoreExample;
import java.util.List;
import org.apache.ibatis.annotations.Param;

public interface ScoreMapper {
  public Score selectscore(int id);
}
在score的model中加上

private Course course;
//get set方法

三 测试

@Test
  public void main(){
       SqlSessionFactory sqlSessionFactory;
       InputStream inputStream;

      try {
          inputStream= Resources.getResourceAsStream("dbconf.xml");
          sqlSessionFactory=new SqlSessionFactoryBuilder().build(inputStream);
          sqlSession=sqlSessionFactory.openSession()；
          //SCORC和course一对一
            ScoreMapper scoreMapper=sqlSession.getMapper(ScoreMapper.class);
            Score score=scoreMapper.selectscore(1);
          System.out.println(score.getCourse().getConame());
    
      } catch (IOException e) {
          e.printStackTrace();
      }finally {
          sqlSession.close();
      }

二：一对多   collection

加入学生表
stud

插件生成对应的接口什么的

<?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="com.ygy.mapper.StudMapper" >
  <resultMap id="stud" type="com.ygy.model.Stud" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Oct 26 15:09:44 CST 2017.
    -->
    <id column="sid" property="sid" jdbcType="INTEGER" />
    <result column="sname" property="sname" jdbcType="VARCHAR" />
    <!--<association property="kc" column="sid" select="com.ygy.mapper.KcMapper.select"/>-->
    <collection property="scoreList" column="sid" select="com.ygy.mapper.ScoreMapper.selectscore"/>     
   <!--collection 将column的数据传到select对应的接口   property映射到列结果的字段或属性-->
  </resultMap>
<select id="selectsud" parameterType="int" resultMap="stud">
  SELECT myba.stud.* FROM  myba.stud WHERE myba.stud.sid=#{id}
</select>
</mapper>

接口

package com.ygy.mapper;

import com.ygy.model.Stud;
import com.ygy.model.StudExample;
import java.util.List;
import org.apache.ibatis.annotations.Param;

public interface StudMapper {
   public Stud selectsud(int id);
}

测试
@Test
  public void main(){
       SqlSessionFactory sqlSessionFactory;
       InputStream inputStream;

      try {
          inputStream= Resources.getResourceAsStream("dbconf.xml");
          sqlSessionFactory=new SqlSessionFactoryBuilder().build(inputStream);
          sqlSession=sqlSessionFactory.openSession();
         　　　　 StudMapper studMapper=sqlSession.getMapper(StudMapper.class);
         　　　　 Stud stud=studMapper.selectsud(1);
          　　　　System.out.println(stud.getScoreList().get(1).getMark());
    　　　　  } catch (IOException e) {
        　　　　  e.printStackTrace();
     　　　　 }finally {
         　　　　 sqlSession.close();
     　　　　 }
结果：