SpringBoot+MyBatis 基于xml实现多表查询的两种方式

1、创建SpringBoot项目，导入依赖

 <dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jdbc</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-jdbc</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.23</version></dependency><!-- https://mvnrepository.com/artifact/org.mybatis/mybatis --><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.4.6</version></dependency><!-- 配置分页依赖 --><!-- https://mvnrepository.com/artifact/com.github.pagehelper/pagehelper --><dependency><groupId>com.github.pagehelper</groupId><artifactId>pagehelper</artifactId><version>5.1.2</version></dependency><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId><version>2.0.0</version></dependency><!-- jdbc启动器 --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-jdbc</artifactId><version>2.2.2.RELEASE</version></dependency><!-- 阿里数据源 --><dependency><groupId>com.alibaba</groupId><artifactId>druid-spring-boot-starter</artifactId><version>1.1.10</version></dependency></dependencies>

2、创建用户和账户数据库表，添加测试数据 (也可以通过程序进行添加，所有增删改查都已经测试完毕，可以直接使用)

create table t_user(
userid int primary key auto_increment,
username varchar(30),
userage int,
height double,
address varchar(30)
);create table t_account(
id int primary key auto_increment,
userid int not null,
money double
);insert into t_user values(null,"唐三",18,176.8,"唐门");
insert into t_user values(null,"小舞",17,166.8,"星斗大森林");insert into t_account values(null,4,89789);
insert into t_account values(null,5,56456);

3、用户信息实体类

package mybatis.bean;
import lombok.Data;@Data
public class UserBean {private Integer userid; //todo 用户IDprivate String username; //todo 用户名称private Integer userage; //todo 用户年龄private double height; //todo 身高private String address; //todo 地址
}

4、用户账户金额实体类

package mybatis.bean;
import lombok.Data;@Data
public class Account {private Integer id; //todo 账户IDprivate Integer userid; //todo 用户IDprivate double money; //todo 金额
}

多表联合查询方式一：通过创建子类方式实现多表联合查询

5、创建子类继承用户信息实体类

package mybatis.bean;
import lombok.Data;@Data
public class UserAccount extends UserBean{private Integer id; //todo 账户IDprivate Integer userid; //todo 用户IDprivate double money; //todo 金额
}

多表联合查询方式二：通过建立实体类关系，只需要在Account实体类中增加一个user属性即可,并生成对应的get和set方法，我使用了@Data注解省略了get及set方法第二种方式最常用

6、用户账户金额实体类将用户信息实体类属性加入

package mybatis.bean;
import lombok.Data;@Data
public class Account {private Integer id; //todo 账户IDprivate Integer userid; //todo 用户IDprivate double money; //todo 金额//todo 用户信息private UserBean userBean; //todo 用户信息实体类
}

7、创建UserDao接口添加@Mapper注解

package mybatis.dao;
import mybatis.bean.Account;
import mybatis.bean.UserAccount;
import mybatis.bean.UserBean;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.springframework.web.bind.annotation.RequestBody;
import java.util.List;
@Mapper
public interface UserDao {//todo 添加int insertUser(@RequestBody UserBean userBean);//todo 根据ID查询UserBean selectUserId(@Param("userid") Integer userid);//todo 根据用户ID修改boolean updateUserId(@RequestBody UserBean userBean);//todo 根据用户ID删除boolean deleteUserId(@Param("userid") Integer userid);//todo 多表联合查询第一种方式//todo 查询所有用户信息及账户金额List<UserAccount> selectAll();//todo 多表联合查询第二种方式//todo 联合查询用户信息及账户金额List<Account> selectUserAndAccount();
}

8、创建UserServer接口

package mybatis.server;
import mybatis.bean.Account;
import mybatis.bean.UserAccount;
import mybatis.bean.UserBean;
import org.apache.ibatis.annotations.Param;
import org.springframework.web.bind.annotation.RequestBody;
import java.util.List;public interface UserServer {//todo 添加int insertUser(@RequestBody UserBean userBean);//todo 根据ID查询UserBean selectUserId(@Param("userid") Integer userid);//todo 根据用户ID修改boolean updateUserId(@RequestBody UserBean userBean);//todo 根据用户ID删除boolean deleteUserId(@Param("userid") Integer userid);//todo 多表联合查询第一种方式//todo 查询所有用户信息及账户金额List<UserAccount> selectAll();//todo 多表联合查询第二种方式//todo 查询用户信息及账户金额List<Account> selectUserAndAccount();
}

9、创建UserServerImpl实现类添加@Server注解

package mybatis.server.impl;
import mybatis.bean.Account;
import mybatis.bean.UserAccount;
import mybatis.bean.UserBean;
import mybatis.dao.UserDao;
import mybatis.server.UserServer;
import org.apache.ibatis.annotations.Param;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.RequestBody;
import javax.annotation.Resource;
import java.util.List;@Service
public class UserServerImpl implements UserServer {@Resourceprivate UserDao userDao;@Overridepublic int insertUser(@RequestBody UserBean userBean) {return userDao.insertUser(userBean);}@Overridepublic UserBean selectUserId(@Param("userid") Integer userid) {return userDao.selectUserId(userid);}@Overridepublic boolean updateUserId(UserBean userBean) {return userDao.updateUserId(userBean);}@Overridepublic boolean deleteUserId(Integer userid) {return userDao.deleteUserId(userid);}//todo 多表联合查询第一种方式@Overridepublic List<UserAccount> selectAll() {return userDao.selectAll();}//todo 多表联合查询第二种方式@Overridepublic List<Account> selectUserAndAccount() {return userDao.selectUserAndAccount();}
}

10、application.yml 配置文件

server:port: 9090spring:datasource:driver-class-name: com.mysql.cj.jdbc.Driverurl: jdbc:mysql://127.0.0.1:3306/test?useSSL=falseusername: rootpassword: roottype: com.alibaba.druid.pool.DruidDataSourcemybatis:configuration:map-underscore-to-camel-case: truemapper-locations: classpath:mapper/*.xmltype-aliases-package: mybatis.bean

11、Usermapper.xml 文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mybatis.dao.UserDao"><!-- 数据库字段和实体类不一致时，使用 resultMap 元素进行配置 --><resultMap id="userResult" type="mybatis.bean.UserBean"><id column="userid" property="userid"></id><result column="username" property="username"></result><result column="userage" property="userage"></result><result column="height" property="height"></result><result column="address" property="address"></result></resultMap><!-- 添加 --><insert id="insertUser" parameterType="UserBean">insert into t_user (userid,username,userage,height,address) values(null,#{username},#{userage},#{height},#{address})</insert><!-- 根据用户ID查询 --><select id="selectUserId" parameterType="Integer" resultMap="userResult">select * from t_user where userid=#{userid}</select><!-- 根据用户ID修改 --><update id="updateUserId" parameterType="UserBean">update t_user set username=#{username},userage=#{userage},height=#{height},address=#{address} where userid=#{userid}</update><!-- 根据用户ID删除 --><delete id="deleteUserId" parameterType="Integer">delete from t_user where userid=#{userid}</delete><!-- 多表联合查询第一种方式 --><!-- 查询所有用户信息及账户余额 --><select id="selectAll" parameterType="java.util.List" resultType="UserAccount">select u.*,a.money,a.id from t_user as u,t_account as a where u.userid = a.userid</select><!-- 多表联合查询第二种方式 --><resultMap id="userAndAccount" type="Account"><id column="id" property="id"></id><result column="userid" property="userid"></result><result column="money" property="money"></result><association column="userid" property="userBean" javaType="mybatis.bean.UserBean"><id column="userid" property="userid"></id><result column="username" property="username"></result><result column="userage" property="userage"></result><result column="height" property="height"></result><result column="address" property="address"></result></association></resultMap><select id="selectUserAndAccount" parameterType="java.util.List" resultMap="userAndAccount">select u.*,a.id,a.money from t_user as u,t_account as a where u.userid = a.userid</select></mapper>

12、创建UserController 控制器类

package mybatis.controller;
import mybatis.bean.Account;
import mybatis.bean.UserAccount;
import mybatis.bean.UserBean;
import mybatis.server.UserServer;
import org.apache.ibatis.annotations.Param;
import org.springframework.data.annotation.Id;
import org.springframework.web.bind.annotation.*;
import javax.annotation.Resource;
import java.util.List;@RestController
@RequestMapping("/userController")
public class UserController {@Resourceprivate UserServer userServer;//@PostMapping("/insertUser")//todo 添加用户信息@RequestMapping(value = "/insertUser", method = RequestMethod.POST)public int insertUser(@RequestBody UserBean userBean) {int user = userServer.insertUser(userBean);if (user == 1) {System.out.println("添加成功!!");} else {System.out.println("添加失败");}return user;}//todo 根据用户ID查询用户信息@GetMapping("/selectUserId")public UserBean selectUserId(@Param("userid") Integer userid) {UserBean userBean = userServer.selectUserId(userid);if (userBean != null) {userBean.getUserid();userBean.getUsername();userBean.getUserage();userBean.getHeight();userBean.getAddress();System.out.println("查询成功" + "  =" + userBean);} else if (userBean == null) {System.out.println("查询失败！！！！");}return userBean;}//todo 根据用户ID修改用户信息@PostMapping("/updateUserId")public boolean updateUserId(@RequestBody UserBean userBean) {boolean user = userServer.updateUserId(userBean);if (user == true) {System.out.println("修改成功！！");} else if (user == false) {System.out.println("修改失败....");}return user;}//todo 根据用户ID删除用户信息@GetMapping("/deleteUserId")public boolean deleteUserId(@Param("userid") Integer userid) {boolean delete = userServer.deleteUserId(userid);if (delete == true) {System.out.println("删除成功！！！！");} else if (delete == false) {System.out.println("删除失败");}return delete;}//todo 多表联合查询第一种方式//todo 查询所有用户信息及账户余额@GetMapping("/selectAll")public List<UserAccount> selectAll() {List<UserAccount> list = userServer.selectAll();if (list.size() >= 1 || list != null) {System.out.println("查询成功!!");} else if (list.size() < 1 || list == null) {System.out.println("查询失败....");}return list;}//todo 多表联合查询第二种方式//todo 查询所有用户信息和账户信息@GetMapping("/selectUserAndAccount")public List<Account> selectUserAndAccount() {List<Account> userAndAccount = userServer.selectUserAndAccount();if (userAndAccount.size() >= 1 || userAndAccount != null) {System.out.println("查询成功");} else if (userAndAccount.size() < 1 || userAndAccount == null) {System.out.println("查询失败。。。");}return userAndAccount;}
}

13、主程序类添加 @Configuration注解

package mybatis;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Configuration;@SpringBootApplication
@Configuration
public class MybatisApplication {public static void main(String[] args) {SpringApplication.run(MybatisApplication.class, args);}
}

14、测试：

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