SpringBoot整合Mybatis

五、多对多实现

    目标：根据id查询运营商拥有的用户和电话信息

1. 构建项目

    使用上一章内容

2.编写代码

1). 实体类Combo

    位于entity包，添加UserCombo集合，添加对应的setter、getter

/** * @author Ray * @date 2018/7/7 0007 * 运营商实体类 */ public class Combo { private int id; private String name; private List<UserCombo> userCombos; public List<UserCombo> getUserCombos() { return userCombos; } public void setUserCombos(List<UserCombo> userCombos) { this.userCombos = userCombos; } 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; } @Override public String toString() { return "Combo{" + "id=" + id + ", name='" + name + '\'' + '}'; } }

2). 实体类UserCombo

    位于entity包，添加User集合，添加对应的setter、getter

/** * @author Ray * @date 2018/7/7 0007 * 用户拥有运营商实体 */ public class UserCombo { private int uid; private int cid; private int price; private List<User> users; private List<Combo> combos; public List<User> getUsers() { return users; } public void setUsers(List<User> users) { this.users = users; } public List<Combo> getCombos() { return combos; } public void setCombos(List<Combo> combos) { this.combos = combos; } public int getUid() { return uid; } public void setUid(int uid) { this.uid = uid; } public int getCid() { return cid; } public void setCid(int cid) { this.cid = cid; } public int getPrice() { return price; } public void setPrice(int price) { this.price = price; } @Override public String toString() { return "UserCombo{" + "uid=" + uid + ", cid=" + cid + ", price=" + price + ", combos=" + combos + '}'; } }

3). 数据操作类ComboMapper

    位于mapper包，添加查询方法selectUserById

/** * @author Ray * @date 2018/7/7 0007 * 数据操作层 */ public interface ComboMapper { /** * 根据id查询运营商拥有的用户和电话信息 */ public Combo selectUserById(Integer id); }

4). ComboMapper类映射ComboMapper.xml

      多对多的理解：就是多个一对多的组合。

<?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.ray.mybatis.mapper.ComboMapper"> <!-- 注意：抽离comboMap --> <resultMap id="comboMap" type="combo"> <id property="id" column="id"/> <result property="name" column="name"/> </resultMap> <!-- 注意：继承comboMap --> <resultMap id="userMap" type="combo" extends="comboMap"> <!-- 一对多 【ofType是映射到list集合属性中pojo的类型】 --> <collection property="userCombos" ofType="userCombo"> <result property="price" column="price"/> <!-- 一对多 --> <collection property="users" ofType="user"> <id property="id" column="uid"/> <result property="name" column="uname"/> <!-- 一对多 【ofType是映射到list集合属性中pojo的类型】 --> <collection property="phones" ofType="phone"> <id property="id" column="pid"/> <result property="name" column="pname"/> <result property="number" column="number"/> </collection> </collection> </collection> </resultMap> <!-- 根据id查询运营商拥有的用户和电话信息 --> <select id="selectUserById" parameterType="int" resultMap="userMap"> SELECT c.*, s.price, u.id uid,u.name uname, p.id pid,p.name pname,p.number FROM combo c, user_combo s, user u, phone p WHERE c.id=s.cid AND s.uid=u.id AND u.id=p.uid and c.id=#{id} </select> </mapper>

5). 数据控制类ComboController

    位于controller包

/** * @author Ray * @date 2018/7/7 0007 * 数据控制层 */ @RestController public class ComboController { @Autowired private ComboMapper comboMapper; /** * 根据id查询运营商拥有的用户和电话信息 * localhost:8080/combo/user/2 */ @GetMapping("/combo/user/{id}") public Combo selectUserById(@PathVariable("id") Integer id){ Combo combo = comboMapper.selectUserById(id); return combo; } }

3. 测试

    根据id查询运营商拥有的客户和电话信息-GET