添加依赖

<?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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.6</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>SpringBoot3mybatis</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>SpringBoot3mybatis</name>
    <description>SpringBoot3mybatis</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.mybatis.spring.boot/mybatis-spring-boot-starter -->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.2.1</version>
        </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>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

配置数据库连接

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/mybatisdb?serverTimezone=UTC&useUnicode=true&charEncoding=utf-8
    username: root
    password: 123456
    driver-class-name: com.mysql.jdbc.Driver

测试连接

测试连接没问题，数据库就连接上了

@SpringBootTest
class SpringBoot3mybatisApplicationTests {
    @Autowired
    DataSource dataSource;
    @Test
    void contextLoads() throws SQLException {
        System.out.println(dataSource.getClass());
        System.out.println(dataSource.getConnection());
    }
}

Mapper接口

package com.example.springboot3mybatis.mapper;
import com.example.springboot3mybatis.pojo.Emp;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Repository;
import java.util.List;
//这个注解表示了这是一个mybatis的mapper类
@Mapper
@Repository
public interface EmpMapper {
    List<Emp> queryEmps();
    Emp queryEmp(int id);
    int addEmp(Emp emp);
}

关于@Repository 与 @Mapper的区别

mybatis的一些配置

注意事项：

• 他妈个逼的，mybatis是和spring同级！同级！同级！复制笔记复制岔了，导致mybatis在spring的子级，报错研究了尼玛一天，没想到在这里。给自己一个警告，下次笔记代码完整复制，不要一句一句的复制。特别是这种对缩进很严格的东西。

关于这个报错：解决org.apache.ibatis.binding.BindingException: Invalid bound statement (not found)问题

mybatis的mapper-locations配置

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/mybatisdb?serverTimezone=UTC&useUnicode=true&charEncoding=utf-8
    username: root
    password: 123456
    driver-class-name: com.mysql.jdbc.Driver
#整合mybatis
mybatis:
  #取别名的包
  type-aliases-package: com.example.springboot3mybatis.pojo
  #mapper映射文件的路径
  mapper-locations: classpath:mybatis/mapper/*.xml
  #下划线驼峰映射
  configuration:
    map-underscore-to-camel-case: true

mapper映射文件

在resource/mybatis/mapper目录下

<?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.example.springboot3mybatis.mapper.EmpMapper">
    <select id="queryEmps" resultType="Emp">
        select*from t_emp
    </select>
    <select id="queryEmp" resultType="Emp">
        select * from t_emp where eid=#{id}
    </select>
    <insert id="addEmp" parameterType="Emp">
        insert t_emp values(null,#{empName},#{age},#{sex},#{email},#{Dept.did})
    </insert>
</mapper>

控制器层

dao，service层就没写，笔记测试代码。
如上配置下来，就能访问接口了

package com.example.springboot3mybatis.controller;
import com.example.springboot3mybatis.mapper.EmpMapper;
import com.example.springboot3mybatis.pojo.Emp;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;
@RestController
public class EmpController {
    @Autowired
    private EmpMapper empMapper;
    @GetMapping("/queryemps")
    public List<Emp> queryEmps() {
        List<Emp> emps = empMapper.queryEmps();
        return emps;
    }
}