Maven+MyBatis 基础程序创建<3>

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一对多关系的代码书写
（这里的例子是班级和学生的关系——一个班级对多个学生）
（这里放主要代码，整个项目的代码：请点击）

Student.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="dao.StudentDao">  <resultMap type="entity.Student" id="map1">    <id column="sid" property="sid"/>    <result column="sname" property="sname"/>    <association property="clazz" javaType="entity.Clazz">      <id column="cid" property="cid"/>      <result column="cname" property="cname"/>    </association>  </resultMap>  <select id="selectAllStudent" resultMap="map1">    select sid,sname,student.cid,cname    from student inner join clazz     on student.cid = clazz.cid      </select></mapper>

Clazz.xml↓(这里为了避免与关键字class重名将所有的班级写为clazz)

<?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="dao.ClazzDao">  <resultMap type="entity.Clazz" id="map1">    <id column="cid" property="cid"/>    <result column="cname" property="cname"/>    <collection property="list" ofType="entity.Student">      <result column="sname" property="sname"/>    </collection>  </resultMap>  <select id="selectAllClazz" resultMap="map1">    select clazz.cid,cname,sname    from clazz inner join student    on clazz.cid = student.cid      </select></mapper>

执行函数Main↓

package main;import java.util.List;import biz.ClazzBiz;import biz.StudentBiz;import entity.Clazz;import entity.Student;public class Main {    public static void main(String[] args) {//      通过学生找班级        StudentBiz biz = new StudentBiz();        List<Student> list = biz.selectAllStudent();        for(Student stu : list) {            System.out.println("学生id："+stu.getSid());            System.out.println("学生姓名："+stu.getSname());            System.out.println("学生班级id：："+stu.getClazz().getCid());            System.out.println("学生班级："+stu.getClazz().getCname());            System.out.println("****************");        }//      通过班级找学生        ClazzBiz biz2 = new ClazzBiz();        List<Clazz> list2 = biz2.selectAllClazz();        for(Clazz cl : list2) {            System.out.println("班级id："+cl.getCid());            System.out.println("班级名称："+cl.getCname());            System.out.println("班级学生：");            for(Student stu : cl.getList()) {                System.out.println("学生姓名："+stu.getSname());            }            System.out.println("******************");        }    }}

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