mybatis的一对多

1、配置文件

db.properties

db.driver=com.mysql.jdbc.Driver
db.url=jdbc:mysql://localhost:3306/demo?useUnicode=true&characterEncoding=utf8
db.username=root
db.password=123456

SqlMapConfig.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>

    <!-- 加载java的配置文件 -->
    <properties resource="config/db.properties"/>
    
    <!-- 配置mybatis的环境信息，与spring整合，该信息由spring来管理 -->
    <environments default="development">
        <environment id="development">
            <!-- 配置JDBC事务控制，由mybatis进行管理 -->
            <transactionManager type="JDBC"></transactionManager>
            <!-- 配置数据源，采用mybatis连接池 -->
            <dataSource type="POOLED">
                <property name="driver" value="${db.driver}" />
                <property name="url" value="${db.url}" />
                <property name="username" value="${db.username}" />
                <property name="password" value="${db.password}" />
            </dataSource>
        </environment>
    </environments>

    <!-- 加载映射文件 -->
    <mappers>
        <mapper resource="config/mapper.xml" />
    </mappers>
    
</configuration>

mapper.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.xiaostudy.domain.Mapper">

    <!-- ========================================================================================== -->
    <!-- 一对多之resultMap1 -->
    <select id="findOfTeacher" resultMap="OfTeacher">
        select * from  teacher t, student s where t.tid=s.tid and t.tid=#{id}
    </select>
    <resultMap type="com.xiaostudy.domain.Teacher" id="OfTeacher">
        <id column="tid" property="tid"/>
        <result column="tname" property="tname"/>
        <collection  property="student" ofType="com.xiaostudy.domain.Student" ><!-- javaType="HashSet" -->
            <id column="sid" property="sid"></id>
            <result column="tid" property="tid"/>
            <result column="sname" property="sname"/>
        </collection>
    </resultMap>
   <!-- ========================================================================================== -->

    <!-- ========================================================================================== -->
    <!-- 一对多之resultMap2 -->
    <select id="findOfTeachers" resultMap="OfTeachers">
        select * from teacher t, student s  where t.tid=s.tid and t.tid=#{id}
    </select>
    <resultMap type="com.xiaostudy.domain.Teacher" id="OfTeachers">
        <id column="tid" property="tid"/>
        <result column="tname" property="tname"/>
        <collection property="student" ofType="com.xiaostudy.domain.Student" select="getStudent" column="tid"/>
    </resultMap>
    
    <select id="getStudent" parameterType="int" resultType="com.xiaostudy.domain.Student">
        select * from student s where s.tid = #{id}
    </select>
   <!-- ========================================================================================== -->

</mapper>

2、domain类

Student.java

package com.xiaostudy.domain;

public class Student {
    private int sid;
    private int tid;
    private String sname;
    private Teacher teacher;

    public int getSid() {
        return sid;
    }

    public void setSid(int sid) {
        this.sid = sid;
    }

    public int getTid() {
        return tid;
    }

    public void setTid(int tid) {
        this.tid = tid;
    }

    public String getSname() {
        return sname;
    }

    public void setSname(String sname) {
        this.sname = sname;
    }

    public Teacher getTeacher() {
        return teacher;
    }

    public void setTeacher(Teacher teacher) {
        this.teacher = teacher;
    }

    @Override
    public String toString() {
        return "Student [sid=" + sid + ", tid=" + tid + ", sname=" + sname
                + ", teacher=" + teacher + "]";
    }

}

Teacher.java

package com.xiaostudy.domain;

import java.util.Set;

public class Teacher {
    private int tid;
    private String tname;
    private Set<Student> student;

    public Set<Student> getStudent() {
        return student;
    }

    public void setStudent(Set<Student> student) {
        this.student = student;
    }

    public int getTid() {
        return tid;
    }

    public void setTid(int tid) {
        this.tid = tid;
    }

    public String getTname() {
        return tname;
    }

    public void setTname(String tname) {
        this.tname = tname;
    }

    @Override
    public String toString() {
        return "Teacher [tid=" + tid + ", tname=" + tname + ", student=" + student + "]";
    }

}

3、代理类Mapper.java

package com.xiaostudy.domain;

import java.util.List;

public interface Mapper {

    // 一对多之resultMap1
    public List<Teacher> findOfTeacher(int id);
    
    // 一对多之resultMap2
    public List<Teacher> findOfTeachers(int id);

}

4、测试类

package com.xiaostudy.test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import com.xiaostudy.domain.Mapper;
import com.xiaostudy.domain.Teacher;

/**
 * @desc 测试类
 * @author xiaostudy
 *
 */
public class MybatisTest {

    public static void main(String[] args) throws IOException {
        String resource = "config/SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);

        // 创建SqlSessionFactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        // 创建SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();

        // 获取一个代理dao实现
        Mapper mapper = sqlSession.getMapper(Mapper.class);
        
        //一对多之resultMap1
        /*List<Teacher> list = mapper.findOfTeacher(1);
        for(Teacher t : list) {
            System.out.println(t);
        }*/
        
        //一对多之resultMap2
        List<Teacher> list = mapper.findOfTeachers(1);
        for(Teacher t : list) {
            System.out.println(t);
        }
        
        sqlSession.close();

    }
    
}

5、数据库

teacher表

student表

 

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