mybatis一对多关系表

一、创建JavaProject

二、导入相关jar包

三、编写配置文件mybatis-comfig.xml

1. 在src目录下新建一个mybatis-comfig.xml文件
2. 编写数据库配置文件db.properties

   driver=com.mysql.jdbc.Driverurl=jdbc\:mysql\://localhost\:3306/test?characterEncoding\=utf8username=rootpassword=123456

   
   

3. <?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><!-- 读取配置文件db.properties中的数据库连接参数 --><properties resource="db.properties"/><!-- 配置实体类的别名 --><typeAliases><!-- <typeAlias type="com.zscs.model.Company" alias="company"/> --><package name="com.zscs.model"/></typeAliases><environments default="development"><environment id="development"><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="com/zscs/model/ClassesMapper.xml"/><mapper resource="com/zscs/model/TeacherMapper.xml"/></mappers></configuration>

四、编写数据表对应的实体类Student，Classes

package com.zscs.model;public class Student {    private Integer sId;    private String sName;    private Integer classId;<span style="white-space:pre"></span>public Integer getClassId() {<span style="white-space:pre"></span>return classId;<span style="white-space:pre"></span>}<span style="white-space:pre"></span>public void setClassId(Integer classId) {<span style="white-space:pre"></span>this.classId = classId;<span style="white-space:pre"></span>}<span style="white-space:pre"></span>private Classes classes;    <span style="white-space:pre"></span>public Classes getClasses() {<span style="white-space:pre"></span>return classes;<span style="white-space:pre"></span>}<span style="white-space:pre"></span>public void setClasses(Classes classes) {<span style="white-space:pre"></span>this.classes = classes;<span style="white-space:pre"></span>}<span style="white-space:pre"></span>public Integer getsId() {        return sId;    }    public void setsId(Integer sId) {        this.sId = sId;    }    public String getsName() {        return sName;    }    public void setsName(String sName) {        this.sName = sName == null ? null : sName.trim();    }}

</pre><pre name="code" class="java">package com.zscs.model;import java.util.List;public class Classes {    private Integer cId;    private String cName;    private Teacher teacher;    private List<Student> students;    public Teacher getTeacher() {return teacher;}public void setTeacher(Teacher teacher) {this.teacher = teacher;}public List<Student> getStudents() {return students;}public void setStudents(List<Student> students) {this.students = students;}public Integer getcId() {        return cId;    }    public void setcId(Integer cId) {        this.cId = cId;    }    public String getcName() {        return cName;    }    public void setcName(String cName) {        this.cName = cName == null ? null : cName.trim();    }}

五、编写上述实体类对应的映射文件StudentMapper.xml，ClassesMapper.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.zscs.model.StudentMapper" >  <resultMap id="BaseResultMap" type="com.zscs.model.Student" >    <id column="s_id" property="sId" jdbcType="INTEGER" />    <result column="s_name" property="sName" jdbcType="VARCHAR" />    <result column="class_id" property="classId" jdbcType="INTEGER" />  </resultMap>  <select id="getStudentById" parameterType="Integer" resultType="Student" resultMap="BaseResultMap">  <span style="white-space:pre"></span>select * from student where s_id=#{id}  </select></mapper>

<?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.zscs.model.ClassesMapper" >  <resultMap id="BaseResultMap" type="Classes" >    <id column="c_id" property="cId" jdbcType="INTEGER" />    <result column="c_name" property="cName" jdbcType="VARCHAR" />    <result column="teacher_id" property="teacherId" jdbcType="INTEGER" />  </resultMap>  <!-- 方法一：多对多联表查询 -->  <resultMap type="Classes" id="MyClassMap">  <id property="cId" column="c_id"/>  <result property="cName" column="c_name"/>  <association property="teacher" javaType="Teacher">  <id column="t_id" property="tId" jdbcType="INTEGER" />    <result column="t_name" property="tName" jdbcType="VARCHAR" />  </association>  <collection property="students" ofType="Student">  <id column="s_id" property="sId" />    <result column="s_name" property="sName" />    <result column="class_id" property="classId" />  </collection>  </resultMap>  <select id="getClassById" parameterType="int" resultMap="MyClassMap">  SELECT * FROM class c,student s,teacher t WHERE c.teacher_id=t.t_id and c.c_id=s.class_id and c.c_id=#{id}  </select>    <!-- 方法二:嵌套查询：通过执行另外一个 SQL 映射语句来返回预期的复杂类型   -->  <select id="getStudents" parameterType="int" resultType="Student">  select s_id sId,s_name sName,class_id classId from student where class_id=#{id}  </select>  <select id="getTeacher" parameterType="int" resultType="Teacher">  select t_id tId,t_name tName from teacher where t_id=#{id}  </select>  <resultMap type="Classes" id="MyClassMap2">  <id property="cId" column="c_id"/>  <result property="cName" column="c_name"/>  <!-- association联合 -->  <association property="teacher" select="getTeacher" column="teacher_id"></association>  <!-- collection采集     -->  <collection property="students" select="getStudents" column="c_id"></collection>  </resultMap>  <select id="getClassById2" parameterType="int" resultMap="MyClassMap2">  SELECT * FROM class where c_id=#{id}  </select></mapper>

六、编写测试类

package com.zscs.mytest;import org.apache.ibatis.session.SqlSession;import org.junit.Test;import com.zscs.model.Classes;import com.zscs.util.MyBatisUtil;public class MyTest {<span style="white-space:pre"></span>@Test<span style="white-space:pre"></span>public void testWord(){<span style="white-space:pre"></span>SqlSession session = MyBatisUtil.getSession();<span style="white-space:pre"></span>String statement="com.zscs.model.ClassesMapper.getClassById2";<span style="white-space:pre"></span>//String statement="com.zscs.model.StudentMapper.getStudentById";<span style="white-space:pre"></span>Classes classes =session.selectOne(statement, 2);<span style="white-space:pre"></span>String students="";<span style="white-space:pre"></span>for(int i=0;i<classes.getStudents().size();i++){<span style="white-space:pre"></span>students+=classes.getStudents().get(i).getsName()+",";<span style="white-space:pre"></span>}<span style="white-space:pre"></span>System.out.println(classes.getcName()+"班上有"+classes.getStudents().size()+"个学生他们分别是"+students+"讲课老师是"+classes.getTeacher().gettName());<span style="white-space:pre"></span>}}