1、配置文件
db.properties
db.driver=com.mysql.jdbc.Driver db.url=jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf8 db.username=root db.password=123456
SqlMapConfig.xml
1 <?xml version="1.0" encoding="UTF-8" ?>
2 <!DOCTYPE configuration
3 PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
4 "http://mybatis.org/dtd/mybatis-3-config.dtd">
5 <configuration>
6
7 <!-- 加载java的配置文件 -->
8 <properties resource="config/db.properties"/>
9
10 <!-- 配置mybatis的环境信息，与spring整合，该信息由spring来管理 -->
11 <environments default="development">
12 <environment id="development">
13 <!-- 配置JDBC事务控制，由mybatis进行管理 -->
14 <transactionManager type="JDBC"></transactionManager>
15 <!-- 配置数据源，采用mybatis连接池 -->
16 <dataSource type="POOLED">
17 <property name="driver" value="${db.driver}" />
18 <property name="url" value="${db.url}" />
19 <property name="username" value="${db.username}" />
20 <property name="password" value="${db.password}" />
21 </dataSource>
22 </environment>
23 </environments>
24
25 <!-- 加载映射文件 -->
26 <mappers>
27 <mapper resource="com/xiaostudy/oneTOmany/mapper.xml" />
28 </mappers>
29
30 </configuration>
mapper.xml
1 <?xml version="1.0" encoding="UTF-8" ?>
2 <!DOCTYPE mapper
3 PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
4 "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
5 <mapper namespace="com.xiaostudy.oneTOmany.Mapper">
6
7 <!-- ========================================================================================== -->
8 <!-- 一对多之resultMap1 -->
9 <select id="findOfTeacher" resultMap="OfTeacher">
10 select * from t_student s, t_teacher t where s.sid=t.tid and t.tid=#{id}
11 </select>
12 <resultMap type="com.xiaostudy.oneTOmany.Teacher" id="OfTeacher">
13 <id column="tid" property="id"/>
14 <result column="tname" property="name"/>
15 <collection property="student" ofType="com.xiaostudy.oneTOmany.Student" ><!-- javaType="HashSet" -->
16 <id column="sid" property="sid"></id>
17 <result column="sname" property="sname"/>
18 </collection>
19 </resultMap>
20 <!-- ========================================================================================== -->
21
22 <!-- ========================================================================================== -->
23 <!-- 一对多之resultMap2 -->
24 <select id="findOfTeachers" resultMap="OfTeachers">
25 select * from t_student2 s, t_teacher t where s.sid=t.tid and t.tid=#{id}
26 </select>
27 <resultMap type="com.xiaostudy.oneTOmany.Teacher" id="OfTeachers">
28 <id column="tid" property="id"/>
29 <result column="tname" property="name"/>
30 <collection property="student" ofType="com.xiaostudy.oneTOmany.Student" select="getStudents" column="sid"/>
31 </resultMap>
32
33 <select id="getStudents" parameterType="int" resultType="com.xiaostudy.oneTOmany.Student">
34 select * from t_student2 s where s.sid = #{id}
35 </select>
36 <!-- ========================================================================================== -->
37
38 <!-- ========================================================================================== -->
39 <!-- 一对多之resultMap3 -->
40 <select id="findOfTeachers2" resultMap="OfTeachers2">
41 select * from t_student2 s, t_teacher t where s.sid=t.tid and t.tid=#{tid}
42 </select>
43 <resultMap type="com.xiaostudy.oneTOmany.Teacher" id="OfTeachers2">
44 <id column="tid" property="id"/>
45 <result column="tname" property="name"/>
46 <collection property="student" ofType="com.xiaostudy.oneTOmany.Student" select="getStudents2" column="id"/>
47 </resultMap>
48
49 <select id="getStudents2" resultType="com.xiaostudy.oneTOmany.Student">
50 select * from t_student2 s where s.sid = #{sid}
51 </select>
52 <!-- ========================================================================================== -->
53 </mapper>
2、domain类
Student.java
1 package com.xiaostudy.oneTOmany;
2
3 public class Student {
4 private int sid;
5 private String sname;
6 private Teacher teacher;
7
8 public int getSid() {
9 return sid;
10 }
11
12 public void setSid(int sid) {
13 this.sid = sid;
14 }
15
16 public String getSname() {
17 return sname;
18 }
19
20 public void setSname(String sname) {
21 this.sname = sname;
22 }
23
24 public Teacher getTeacher() {
25 return teacher;
26 }
27
28 public void setTeacher(Teacher teacher) {
29 this.teacher = teacher;
30 }
31
32 @Override
33 public String toString() {
34 return "Student [sid=" + sid + ", sname=" + sname + ", teacher=" + teacher + "]";
35 }
36
37 }
Teacher.java
1 package com.xiaostudy.oneTOmany;
2
3 import java.util.Set;
4
5 public class Teacher {
6 private int id;
7 private String name;
8 private Set<Student> student;
9
10 public Set<Student> getStudent() {
11 return student;
12 }
13
14 public void setStudent(Set<Student> student) {
15 this.student = student;
16 }
17
18 public int getId() {
19 return id;
20 }
21
22 public void setId(int id) {
23 this.id = id;
24 }
25
26 public String getName() {
27 return name;
28 }
29
30 public void setName(String name) {
31 this.name = name;
32 }
33
34 @Override
35 public String toString() {
36 return "Teacher [id=" + id + ", name=" + name + ", student=" + student + "]";
37 }
38
39 }
3、代理类Mapper.java
1 package com.xiaostudy.oneTOmany;
2
3 import java.util.List;
4
5 public interface Mapper {
6
7 // 一对多之resultMap1
8 public List<Teacher> findOfTeacher(int id);
9
10 // 一对多之resultMap2
11 public List<Teacher> findOfTeachers(int id);
12
13 // 一对多之resultMap3
14 public Teacher findOfTeachers2(int id);
15
16 }
4、测试类
1 package com.xiaostudy.oneTOmany;
2
3 import java.io.IOException;
4 import java.io.InputStream;
5 import java.util.List;
6 import java.util.Set;
7
8 import org.apache.ibatis.io.Resources;
9 import org.apache.ibatis.session.SqlSession;
10 import org.apache.ibatis.session.SqlSessionFactory;
11 import org.apache.ibatis.session.SqlSessionFactoryBuilder;
12 import com.xiaostudy.oneTOmany.Teacher;
13
14 /**
15 * @desc 测试类
16 * @author xiaostudy
17 *
18 */
19 public class MybatisTest {
20
21 public static void main(String[] args) throws IOException {
22 String resource = "config/SqlMapConfig.xml";
23 InputStream inputStream = Resources.getResourceAsStream(resource);
24
25 // 创建SqlSessionFactory
26 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
27
28 // 创建SqlSession
29 SqlSession sqlSession = sqlSessionFactory.openSession();
30
31 // 获取一个代理dao实现
32 Mapper mapper = sqlSession.getMapper(Mapper.class);
33
34 //一对多之resultMap1
35 // List<Teacher> list = mapper.findOfTeacher(3);
36
37 //一对多之resultMap2
38 List<Teacher> list = mapper.findOfTeachers(2);
39 /*Teacher teacher = list.get(0);
40 System.out.println(teacher.getId());
41 System.out.println(teacher.getName());
42 Set<Student> student = teacher.getStudent();
43 for(Student s : student) {
44 System.out.println(s);
45 }*/
46 //一对多之resultMap3
47 // Teacher t = mapper.findOfTeachers2(2);
48
49 for(Teacher t : list) {
50 System.out.println(t);
51 }
52
53 // System.out.println(list.get(0));
54 // System.out.println(t);
55 // System.out.println(list);
56
57 sqlSession.close();
58
59 }
60
61 }
5、数据库
t_teacher表
t_student2表
mybatis的一对多
原文地址：https://www.cnblogs.com/xiaostudy/p/9588985.html
时间： 2024-11-05 13:04:24