首页 > > 程序设计 > Java技术 >

5、SpringBoot+Mybatis整合------多对多

2018-06-27 09:44:46来源：博客园阅读 ()

开发工具：STS

代码下载链接：https://github.com/theIndoorTrain/SpringBoot_Mybatis/tree/3baea10a3a1104bda815c206954b2b687511aa3d

前言：

之前我们探讨了一对一、一对多的映射关系，今天我们来讨论多对多的映射关系。

多对多，其实可以拆成多个一对多来理解。

比如：

学生-------课程----------学生选课的关系：

（1）查询某个学生所选的全部课程；

（2）查询选修某个课程的全部学生；

今天我们就来实现这个实例。

一、数据库建表：

1.student表：

2.course表：

3.student-course表：

二、查询某个学生所选的全部课程代码实现：

1.代码实现：

（1）添加Course实体：

 1 package com.xm.pojo;
 2 /**
 3  * 课程实体
 4  * @author xm
 5  *
 6  */
 7 public class Course {
 8     private int id;
 9     private String name;
10     public int getId() {
11         return id;
12     }
13     public void setId(int id) {
14         this.id = id;
15     }
16     public String getName() {
17         return name;
18     }
19     public void setName(String name) {
20         this.name = name;
21     }
22     
23 
24 }

Course.java

（2）添加StudntCourse实体：

 1 package com.xm.pojo;
 2 
 3 import java.util.List;
 4 /**
 5  * 学生选课实体
 6  * @author xm
 7  *
 8  */
 9 public class StudentCourse {
10     
11     private int sid;
12     private int cid;
13     private int sorce;
14     
15     private List<Student> students;
16     private List<Course> courses;
17     public int getSid() {
18         return sid;
19     }
20     public void setSid(int sid) {
21         this.sid = sid;
22     }
23     public int getCid() {
24         return cid;
25     }
26     public void setCid(int cid) {
27         this.cid = cid;
28     }
29     public int getSorce() {
30         return sorce;
31     }
32     public void setSorce(int sorce) {
33         this.sorce = sorce;
34     }
35     public List<Student> getStudents() {
36         return students;
37     }
38     public void setStudents(List<Student> students) {
39         this.students = students;
40     }
41     public List<Course> getCourses() {
42         return courses;
43     }
44     public void setCourses(List<Course> courses) {
45         this.courses = courses;
46     }
47     
48     
49 
50 }

StudentCourse.java

（3）在Studnent实体中添加StudentCourse列表：

 1 package com.xm.pojo;
 2 
 3 import java.util.List;
 4 
 5 /**
 6  * name:学生实体
 7  * @author xxm
 8  *
 9  */
10 public class Student {
11     /**
12      * content:主键id
13      */
14     private int id;
15     /**
16      * content:姓名
17      */
18     private String name;
19     
20     private List<Book> books;
21     
22     private List<StudentCourse> studentCourses;
23     
24     public Student() {
25         // TODO Auto-generated constructor stub
26     }
27     
28     
29     public List<StudentCourse> getStudentCourses() {
30         return studentCourses;
31     }
32 
33 
34     public void setStudentCourses(List<StudentCourse> studentCourses) {
35         this.studentCourses = studentCourses;
36     }
37 
38 
39     public List<Book> getBooks() {
40         return books;
41     }
42 
43 
44     public void setBooks(List<Book> books) {
45         this.books = books;
46     }
47 
48 
49     public int getId() {
50         return id;
51     }
52     public void setId(int id) {
53         this.id = id;
54     }
55     public String getName() {
56         return name;
57     }
58     public void setName(String name) {
59         this.name = name;
60     }
61     
62     
63 
64 }

Student.java

（4）在数据库操作接口中添加方法：

 1 package com.xm.mapper;
 2 
 3 import java.util.List;
 4 
 5 import com.xm.pojo.Student;
 6 
 7 public interface StudentMapper {
 8 
 9     /***********/
10 
11     /**
12      * 根据学生id查询该学生选修的所有课程
13      * @param id
14      * @return
15      */
16     public Student selectCourseById(Integer id);
17     
18 }

StudentMapper.java

（5）完善mapper映射：

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
 3 <mapper namespace="com.xm.mapper.StudentMapper">
 4 
 5     
 6     
 7     <resultMap type="student" id="studentMap">
 8         <id property="id" column="id"/>
 9         <result property="name" column="name"/>
10     </resultMap>
11     
12     
13     
14     <resultMap type="student" id="courseMap" extends="studentMap">
15         <collection property="studentCourses" ofType="studentCourse">
16             <result property="sorce" column="sorce"/>
17             <collection property="courses" ofType="course">
18                 <id property="id" column="cid"/>
19                 <result property="name" column="cname"/>
20             </collection>
21         </collection>
22     </resultMap>
23 
24         <!-- 根据学生id查询该学生选修的所有课程 -->
25     <select id="selectCourseById" parameterType="int" resultMap="courseMap" >
26         select a.*,b.sorce,c.id cid,c.name cname from student a,student_course b,course c where a.id=b.sid and b.cid=c.id and a.id=#{id}
27     </select>
28 </mapper>

StudentMapper.xml

（6）在controller中实现：

 1 package com.xm.controller;
 2 
 3 import java.util.List;
 4 
 5 import javax.websocket.server.PathParam;
 6 
 7 import org.springframework.beans.factory.annotation.Autowired;
 8 import org.springframework.web.bind.annotation.DeleteMapping;
 9 import org.springframework.web.bind.annotation.GetMapping;
10 import org.springframework.web.bind.annotation.PathVariable;
11 import org.springframework.web.bind.annotation.PostMapping;
12 import org.springframework.web.bind.annotation.PutMapping;
13 import org.springframework.web.bind.annotation.RestController;
14 
15 import com.xm.mapper.StudentMapper;
16 import com.xm.pojo.Student;
17 
18 @RestController
19 public class StudentController {
20     @Autowired
21     private StudentMapper studentMapper;
22     
23     /************/
24     
25     /**
26      * 根据学生id查询该学生选修的所有课程
27      * @param id
28      * @return
29      */
30     @GetMapping("/student/course/{id}")
31     public Student selectCourseById(@PathVariable("id") Integer id) {
32         Student student = studentMapper.selectCourseById(id);
33         return student;
34     }
35 
36 }

StudentController.java

2.测试结果：

（1）数据库运行

2.postman运行：

三、查询选修某个课程的全部学生代码实现：

1.代码实现：

（1）Course实体中添加StudentCourse列表：

 1 package com.xm.pojo;
 2 
 3 import java.util.List;
 4 
 5 /**
 6  * 课程实体
 7  * @author xm
 8  *
 9  */
10 public class Course {
11     private int id;
12     private String name;
13     private List<StudentCourse> studentCourses;
14     
15     public List<StudentCourse> getStudentCourses() {
16         return studentCourses;
17     }
18     public void setStudentCourses(List<StudentCourse> studentCourses) {
19         this.studentCourses = studentCourses;
20     }
21     public int getId() {
22         return id;
23     }
24     public void setId(int id) {
25         this.id = id;
26     }
27     public String getName() {
28         return name;
29     }
30     public void setName(String name) {
31         this.name = name;
32     }
33     
34 
35 }

Course.java

（2）添加Course数据操作接口：

 1 package com.xm.mapper;
 2 
 3 import com.xm.pojo.Course;
 4 
 5 public interface CourseMapper {
 6     /**
 7      * 根据课程id查询选修此课程的全部学生
 8      * @param id
 9      * @return
10      */
11     public Course selectStudentById(Integer id);
12 
13 }

CourseMapper.java

（3）添加mapper映射：

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
 3 <mapper namespace="com.xm.mapper.CourseMapper">
 4     <resultMap type="course" id="courseMap">
 5         <id property="id" column="id"/>
 6         <result property="name" column="name"/>
 7     </resultMap>
 8     <resultMap type="course" id="studentMap" extends="courseMap">
 9         <collection property="studentCourses" ofType="studentCourse">
10             <result property="sorce" column="sorce"/>
11             <collection property="students" ofType="student">
12                 <id property="id" column="sid"/>
13                 <result property="name" column="sname"/>
14             </collection>
15         </collection>
16     </resultMap>
17     <!-- 根据课程id查询选修此课程的全部学生 -->
18     <select id="selectStudentById" parameterType="int" resultMap="studentMap">
19     select a.*,b.sorce,c.id sid,c.name sname from student c,student_course b,course a where a.id=b.cid and b.sid=c.id and a.id=#{id}
20     </select>
21 </mapper>

CourseMapper.xml

（4）添加controller：

 1 package com.xm.controller;
 2 
 3 import org.springframework.beans.factory.annotation.Autowired;
 4 import org.springframework.web.bind.annotation.GetMapping;
 5 import org.springframework.web.bind.annotation.PathVariable;
 6 import org.springframework.web.bind.annotation.RestController;
 7 
 8 import com.xm.mapper.CourseMapper;
 9 import com.xm.pojo.Course;
10 
11 /**
12  * 课程
13  * @author xm
14  *
15  */
16 @RestController
17 public class CourseController {
18     @Autowired
19     private CourseMapper  courseMapper;
20     
21     /**
22      * 根据课程id查询选修此课程的全部学生
23      * @param id
24      * @return
25      */
26     @GetMapping("/course/student/{id}")
27     public Course selectStudentById(@PathVariable("id")Integer id) {
28         
29         Course course = courseMapper.selectStudentById(id);
30         return course;
31         
32     }
33 
34 }