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3、SpringBoot+Mybatis整合------一对多

2018-06-21 06:54:19来源：未知阅读 ()

开发工具：STS

代码下载链接：https://github.com/theIndoorTrain/SpringBoot_Mybatis/tree/c00b56dbd51a1e26ab9fd990201ad9e89a770ca9

前言：

今天探讨的是Mybatis一对多的处理关系。

一个人有好多本书，每本书的主人只有一个人。当我们查询某个人拥有的所有书籍时，就涉及到了一对多的映射关系。

一、添加数据表：

二、代码实现：

1.添加Book实体：

 1 package com.xm.pojo;
 2 /**
 3  * 书的实体
 4  * @author xm
 5  *
 6  */
 7 public class Book {
 8     
 9     private int id;
10     private int sid;
11     private String name;
12     private double price;
13     public int getId() {
14         return id;
15     }
16     public void setId(int id) {
17         this.id = id;
18     }
19     public int getSid() {
20         return sid;
21     }
22     public void setSid(int sid) {
23         this.sid = sid;
24     }
25     public String getName() {
26         return name;
27     }
28     public void setName(String name) {
29         this.name = name;
30     }
31     public double getPrice() {
32         return price;
33     }
34     public void setPrice(double price) {
35         this.price = price;
36     }
37     
38     
39 
40 }

Book.java

2.在Student实体中添加book集合：

 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     public Student() {
23         // TODO Auto-generated constructor stub
24     }
25     
26     
27     public List<Book> getBooks() {
28         return books;
29     }
30 
31 
32     public void setBooks(List<Book> books) {
33         this.books = books;
34     }
35 
36 
37     public int getId() {
38         return id;
39     }
40     public void setId(int id) {
41         this.id = id;
42     }
43     public String getName() {
44         return name;
45     }
46     public void setName(String name) {
47         this.name = name;
48     }
49     
50     
51 
52 }

Student.java

3.在StudentMapper接口中定义查询方法：

 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      * 根据id查询
11      * @param id
12      * @return
13      */
14     public Student getById(Integer id);
15     
16     /**
17      * 查询全部
18      * @return
19      */
20     public List<Student> list();
21     
22     /**
23      * 插入
24      * @param student
25      */
26     public int insert(Student student);
27     /**
28      * 主键回填的插入
29      * @param student
30      * @return
31      */
32     public int insertToId(Student student);
33     
34     /**
35      * 根据student的id修改
36      * @param student
37      */
38     public void update(Student student);
39     
40     /**
41      * 根据id删除
42      * @param id
43      */
44     public void delete(Integer id);
45     
46     /**
47      * 根据id查询所有的书
48      * @param id
49      */
50     public Student selectBookById(Integer id);
51     
52 }

StudentMapper.java

4.在mapper映射关系中，添加一对多的select和resaultMap：

注意：当多个表的字段名一样的时候，查询需要用别名。

 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     <!-- 根据id查询 -->
 6     <select id="getById" parameterType="int" resultType="student">
 7     select * from student where id=#{id}
 8     </select>
 9     <!-- 查询所有 -->
10     <select id="list" parameterType="int" resultType="student">
11     select * from student
12     </select>
13     
14     <!-- 插入一个学生 -->
15     <insert id="insert" parameterType="student">
16     insert into student(name) values(#{name})
17     </insert>
18     <!-- 主键回填的插入 -->
19     <insert id="insertToId" parameterType="student" useGeneratedKeys="true" keyProperty="id">
20     insert into student(name) values(#{name})
21     </insert>
22     
23     <!-- 根据id修改学生信息 -->
24     <update id="update" parameterType="student">
25     update student set name=#{name} where id=#{id}
26     </update>
27     
28     <!-- 根据id删除学生 -->
29     <delete id="delete" parameterType="int">
30     delete  from student where id=#{id}
31     </delete>
32     
33     <resultMap type="student" id="bookMap">
34         <id property="id" column="id"/>
35         <result property="name" column="name"/>
36         <collection property="books" ofType="book">
37             <id property="id" column="bid"/>
38             <result property="name" column="bname"/>
39             <result property="price" column="price"/>
40         </collection>
41     </resultMap>
42     <!--根据id查询所有的书  -->
43     <select id="selectBookById" parameterType="int" resultMap="bookMap">
44     select a.*,b.id bid,b.name bname,b.price from student a,book b where a.id=b.sid and a.id=#{id};
45     </select>
46 </mapper>

StudentMapper.xml

5.在StudentController中实现查询：

 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      * 根据id查询学生
25      * @param id
26      * @return
27      */
28     @GetMapping("/student/{id}")
29     public Student getById(@PathVariable("id") Integer id) {
30         
31         Student student = studentMapper.getById(id);
32         return student;
33         
34     }
35     
36     /**
37      * 查询全部
38      * @return
39      */
40     @GetMapping("/students")
41     public List<Student> list(){
42         List<Student> students = studentMapper.list();
43         return students;
44     }
45     
46     /**
47      * 插入
48      * @param student
49      */
50     @PostMapping("/student")
51     public void insert( Student student) {
52         studentMapper.insert(student);
53     }
54     
55     /**
56      * 修改
57      * @param student
58      */
59     @PutMapping("/student/{id}")
60     public void update(Student student,@PathVariable("id")Integer id) {
61         studentMapper.update(student);
62     }
63     
64     /**
65      * 根据id删除
66      * @param id
67      */
68     @DeleteMapping("/student/{id}")
69     public void delete(@PathVariable("id") Integer id) {
70         studentMapper.delete(id);
71     }
72     
73     /**
74      * 根据id查询所有的书
75      */
76     @GetMapping("/student/book/{id}")
77     public Student getBooks(@PathVariable("id") Integer id) {
78         Student student = studentMapper.selectBookById(id);
79         return student;
80     }
81 
82 }