4、SpringBoot+Mybatis整合------一对多

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:

图片描述

二、代码实现:

1.添加Book实体:

图片描述

图片描述

 package com.xm.pojo;
 /**
  * 书的实体
  * @author xm
  *
  */
 public class Book {
     
     private int id;
     private int sid;
     private String name;
     private double price;
     public int getId() {
         return id;
     }
     public void setId(int id) {
         this.id = id;
     }
     public int getSid() {
         return sid;
     }
     public void setSid(int sid) {
         this.sid = sid;
     }
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     public double getPrice() {
         return price;
     }
     public void setPrice(double price) {
         this.price = price;
     }
     
     
 
 }

Book.java

2.在Student实体中添加book集合:

图片描述

图片描述

 package com.xm.pojo;
 
 import java.util.List;
 
 /**
  * name:学生实体
  * @author xxm
  *
  */
 public class Student {
     /**
      * content:主键id
      */
     private int id;
     /**
      * content:姓名
      */
     private String name;
     
     private List<Book> books;
     
     public Student() {
         // TODO Auto-generated constructor stub
     }
     
     
     public List<Book> getBooks() {
         return books;
     }
 
 
     public void setBooks(List<Book> books) {
         this.books = books;
     }
 
 
     public int getId() {
         return id;
     }
     public void setId(int id) {
         this.id = id;
     }
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     
     
 
 }

Student.java

3.在StudentMapper接口中定义查询方法:

图片描述

图片描述

 package com.xm.mapper;
 
 import java.util.List;
 
 import com.xm.pojo.Student;
 
 public interface StudentMapper {
 
     /**
      * 根据id查询
      * @param id
      * @return
      */
     public Student getById(Integer id);
     
     /**
      * 查询全部
      * @return
      */
     public List<Student> list();
     
     /**
      * 插入
      * @param student
      */
     public int insert(Student student);
     /**
      * 主键回填的插入
      * @param student
      * @return
      */
     public int insertToId(Student student);
     
     /**
      * 根据student的id修改
      * @param student
      */
     public void update(Student student);
     
     /**
      * 根据id删除
      * @param id
      */
     public void delete(Integer id);
     
     /**
      * 根据id查询所有的书
      * @param id
      */
     public Student selectBookById(Integer id);
     
 }

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。

图片描述

图片描述

 <?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.xm.mapper.StudentMapper">
 
     <!-- 根据id查询 -->
     <select id="getById" parameterType="int" resultType="student">
     select * from student where id=#{id}
     </select>
     <!-- 查询所有 -->
     <select id="list" parameterType="int" resultType="student">
     select * from student
     </select>
     
     <!-- 插入一个学生 -->
     <insert id="insert" parameterType="student">
     insert into student(name) values(#{name})
     </insert>
     <!-- 主键回填的插入 -->
     <insert id="insertToId" parameterType="student" useGeneratedKeys="true" keyProperty="id">
     insert into student(name) values(#{name})
     </insert>
     
     <!-- 根据id修改学生信息 -->
     <update id="update" parameterType="student">
     update student set name=#{name} where id=#{id}
     </update>
     
     <!-- 根据id删除学生 -->
     <delete id="delete" parameterType="int">
     delete  from student where id=#{id}
     </delete>
     
     <resultMap type="student" id="bookMap">
         <id property="id" column="id"/>
         <result property="name" column="name"/>
         <collection property="books" ofType="book">
             <id property="id" column="bid"/>
             <result property="name" column="bname"/>
             <result property="price" column="price"/>
         </collection>
     </resultMap>
     <!--根据id查询所有的书  -->
     <select id="selectBookById" parameterType="int" resultMap="bookMap">
     select a.*,b.id bid,b.name bname,b.price from student a,book b where a.id=b.sid and a.id=#{id};
     </select>
 </mapper>

StudentMapper.xml

5.在StudentController中实现查询:

图片描述

图片描述

 package com.xm.controller;
 
 import java.util.List;
 
 import javax.websocket.server.PathParam;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.web.bind.annotation.DeleteMapping;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.PutMapping;
 import org.springframework.web.bind.annotation.RestController;
 
 import com.xm.mapper.StudentMapper;
 import com.xm.pojo.Student;
 
 @RestController
 public class StudentController {
     @Autowired
     private StudentMapper studentMapper;
     
     /**
      * 根据id查询学生
      * @param id
      * @return
      */
     @GetMapping("/student/{id}")
     public Student getById(@PathVariable("id") Integer id) {
         
         Student student = studentMapper.getById(id);
         return student;
         
     }
     
     /**
      * 查询全部
      * @return
      */
     @GetMapping("/students")
     public List<Student> list(){
         List<Student> students = studentMapper.list();
         return students;
     }
     
     /**
      * 插入
      * @param student
      */
     @PostMapping("/student")
     public void insert( Student student) {
         studentMapper.insert(student);
     }
     
     /**
      * 修改
      * @param student
      */
     @PutMapping("/student/{id}")
     public void update(Student student,@PathVariable("id")Integer id) {
         studentMapper.update(student);
     }
     
     /**
      * 根据id删除
      * @param id
      */
     @DeleteMapping("/student/{id}")
     public void delete(@PathVariable("id") Integer id) {
         studentMapper.delete(id);
     }
     
     /**
      * 根据id查询所有的书
      */
     @GetMapping("/student/book/{id}")
     public Student getBooks(@PathVariable("id") Integer id) {
         Student student = studentMapper.selectBookById(id);
         return student;
     }
 
 }

StudentController.java

三、测试结果:

1.数据库查询结果:

图片描述

2.postman访问结果:

图片描述

                                                                    2018-06-20