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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