注释很详细，直接上代码

项目结构

源码

UserMapper

package com.amoorzheyu.mapper;

import com.amoorzheyu.pojo.User;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;

import java.util.List;

@Mapper //在运行时生成代理类，并交给 IOC容器 管理
public interface UserMapper {

        //查看全部用户信息
        @Select("select * from user")
        public List<User> getAllUsers();

}

User

package com.amoorzheyu.pojo;

public class User {
    private Integer id;
    private String name;
    private Short age;
    private  String phone;

    public User() {//无参构造函数
    }

    //有参构造函数
    public User(Integer id, String name, Short age, String phone) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.phone = phone;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", phone='" + phone + '\'' +
                '}';
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Short getAge() {
        return age;
    }

    public void setAge(Short age) {
        this.age = age;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }
}

SpringBootStudy2Application

package com.amoorzheyu;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringBootStudy2Application {

    public static void main(String[] args) {
        SpringApplication.run(SpringBootStudy2Application.class, args);
    }
}

application.properties

#下面这些内容是为了让MyBatis映射
#指定Mybatis的Mapper文件
mybatis.mapper-locations=classpath:mappers/*xml
#指定Mybatis的实体目录
mybatis.type-aliases-package=com.amoorzheyu.mybatis.entity
# 应用服务 WEB 访问端口
server.port=8080

# 数据库驱动类名
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

# 数据库连接地址
spring.datasource.url=jdbc:mysql://localhost:3306/spring-boot-study-database?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=UTC

# 数据库用户名
spring.datasource.username=root

# 数据库密码
spring.datasource.password=1234

SpringBootStudy2ApplicationTests

package com.amoorzheyu;

import com.amoorzheyu.mapper.UserMapper;
import com.amoorzheyu.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.List;

@SpringBootTest
class SpringBootStudy2ApplicationTests {

    @Autowired// 注入bean
    private UserMapper userMapper;

    @Test
    void contextLoads() {
        List <User> users = userMapper.getAllUsers();

        users.stream().forEach(user -> System.out.println(user));
    }
}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.amoorzheyu</groupId>
    <artifactId>spring-boot-study-2</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>spring-boot-study-2</name>
    <description>spring-boot-study-2</description>
    <properties>
        <java.version>1.8</java.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <spring-boot.version>2.6.13</spring-boot.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.2.2</version>
        </dependency>

        <dependency>
            <groupId>com.mysql</groupId>
            <artifactId>mysql-connector-j</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${spring-boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>${spring-boot.version}</version>
                <configuration>
                    <mainClass>com.amoorzheyu.SpringBootStudy2Application</mainClass>
                    <skip>true</skip>
                </configuration>
                <executions>
                    <execution>
                        <id>repackage</id>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

数据库内容

/*
 Navicat MySQL Data Transfer

 Source Server         : localhost_3306
 Source Server Type    : MySQL
 Source Server Version : 80100
 Source Host           : localhost:3306
 Source Schema         : spring-boot-study-database

 Target Server Type    : MySQL
 Target Server Version : 80100
 File Encoding         : 65001

 Date: 16/09/2024 16:38:59
*/

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for user
-- ----------------------------
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user`  (
  `id` int NOT NULL AUTO_INCREMENT COMMENT '用户id',
  `name` varchar(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL,
  `age` tinyint NULL DEFAULT NULL,
  `phone` varchar(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_0900_ai_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of user
-- ----------------------------
INSERT INTO `user` VALUES (1, '小白', 20, '111222333444555');
INSERT INTO `user` VALUES (2, '大黄', 38, '8888888888888');

SET FOREIGN_KEY_CHECKS = 1;

效果演示