mybatis的一对多

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： 2024-08-30 01:32:34

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