实体类

所有实体类的定义如下：

Teacher 类

java

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package com.xinzhi.pojo; import lombok.AllArgsConstructor; import lombok.Builder; import lombok.Data; import lombok.NoArgsConstructor; import java.util.List; @Data @NoArgsConstructor @AllArgsConstructor @Builder public class Teacher { private int id; private String name; private String size; private int age; private List<User> users; }

User 类

java

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package com.xinzhi.pojo; import lombok.AllArgsConstructor; import lombok.Builder; import lombok.Data; import lombok.NoArgsConstructor; import java.util.List; @Data @NoArgsConstructor @AllArgsConstructor @Builder public class User { private Integer id; private String username; private String password; private Integer age; private String phone; private List<Card> cards; private List<Account> accounts; }

Card 类

java

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package com.xinzhi.pojo; import lombok.AllArgsConstructor; import lombok.Builder; import lombok.Data; import lombok.NoArgsConstructor; @Data @NoArgsConstructor @AllArgsConstructor @Builder public class Card { private int id; private String num; private int uid; }

Account 类

java

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package com.xinzhi.pojo; import lombok.AllArgsConstructor; import lombok.Builder; import lombok.Data; import lombok.NoArgsConstructor; @Data @NoArgsConstructor @AllArgsConstructor @Builder public class Account { private Integer id; private String name; private Double money; private int tid; }

MyBatis 映射配置

确保 MyBatis 的映射配置正确，尤其是列名和属性名的映射。

xml

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<?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.xinzhi.mapper.TeacherMapper"> <!-- 定义 resultMap --> <resultMap id="teacherMap" type="com.xinzhi.pojo.Teacher"> <id column="teacher_id" property="id"/> <result column="teacher_name" property="name"/> <result column="teacher_size" property="size"/> <result column="teacher_age" property="age"/> <collection property="users" ofType="com.xinzhi.pojo.User"> <id column="user_id" property="id"/> <result column="username" property="username"/> <result column="password" property="password"/> <result column="user_age" property="age"/> <result column="phone" property="phone"/> <collection property="cards" ofType="com.xinzhi.pojo.Card"> <id column="card_id" property="id"/> <result column="num" property="num"/> <result column="uid" property="uid"/> </collection> <collection property="accounts" ofType="com.xinzhi.pojo.Account"> <id column="account_id" property="id"/> <result column="account_name" property="name"/> <result column="account_money" property="money"/> <result column="tid" property="tid"/> </collection> </collection> </resultMap> <!-- 编写 SQL 查询 --> <select id="queryTeacher" resultMap="teacherMap"> <![CDATA[ SELECT t.id AS teacher_id, t.name AS teacher_name, t.size AS teacher_size, t.age AS teacher_age, u.id AS user_id, u.username, u.password, u.age AS user_age, u.phone, c.id AS card_id, c.num, c.uid AS user_id, a.id AS account_id, a.name AS account_name, a.money AS account_money, a.tid FROM teacher t JOIN account a ON t.id = a.tid JOIN user u ON a.id = u.id JOIN card c ON u.id = c.uid ]]> </select> </mapper>

关键点说明

1. 实体类: 确保实体类的字段名与数据库表的列名一致，并使用 Lombok 注解来自动生成 getter 和 setter。
2. SQL 语句: 在 SQL 查询中使用 c.uid AS user_id 确保返回的列名与 resultMap 中的列名一致。
3. MyBatis 映射: 确保 resultMap 中的 property 和 column 一一对应。

通过上述配置，您应该能够正确地执行多表联查，并解决 c.user_id 列不存在的问题。如果仍然遇到错误，请确保数据库中确实存在所有列，并且名称与映射配置一致。