1. 导入依赖

我使用MySQL，需要导入MySQL的驱动依赖
此外要在SpringBoot中使用Mybatis，则需要导入Mybatis启动器

        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.2.2</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.33</version>
        </dependency>

需要注意版本对应关系，我是用springboot2.7.14，则需要导入2.2或2.3的Mybatis启动器
在这里插入图片描述

2. 配置文件

在springboot的yaml配置文件中把连接数据库所需的spring.datasource和mybatis.mapper-locations配置好。

mapper-locations我设置的是classpath:mapper/*.xml，一般都是在
resource目录下创建一个mapper文件夹，然后把所有的mapper.xml放进去。因此mapper-locations设置为classpath:mapper/*.xml的意思就是扫描mapper文件夹下的所有xml文件作为mybatis的mapper
spring.datasource则就是数据库连接所需的driver、url、username、password

mybatis:
  mapper-locations: classpath:mapper/*.xml
spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/mytest
    username: root
    password: root

3. 业务场景

dao层创建一个Mapper接口，注意需要用@Mapper标记

@Mapper
public interface UserMapper {
    User getUserByID(int id);
}

对应的在resource/mapper下创建对应的Mapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.wonder.mapper.UserMapper">
    <select id="getUserByID" parameterType="int" resultType="com.wonder.entity.User">
        select * from users where id=#{id}
    </select>
</mapper>

其中用到的entity

package com.wonder.entity;
public class User {
  private long id;
  private String name;
  private String username;
  private String password;
  private java.sql.Timestamp createtime;
  private long roleid;

  public long getId() {
    return id;
  }

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


  public String getName() {
    return name;
  }

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

  public String getUsername() {
    return username;
  }

  public void setUsername(String username) {
    this.username = username;
  }

  public String getPassword() {
    return password;
  }

  public void setPassword(String password) {
    this.password = password;
  }

  public java.sql.Timestamp getCreatetime() {
    return createtime;
  }

  public void setCreatetime(java.sql.Timestamp createtime) {
    this.createtime = createtime;
  }

  public long getRoleid() {
    return roleid;
  }

  public void setRoleid(long roleid) {
    this.roleid = roleid;
  }
}

用到的数据库表和其中的数据
在这里插入图片描述

4. Service层和Controller层

public interface UserService {
    User getUserByID(int id);
}

@Service
public class UserServiceImpl implements UserService {
    @Autowired
    UserMapper userMapper;

    @Override
    public User getUserByID(int id) {
        return userMapper.getUserByID(id);
    }
}

@Controller
public class UserController {
    @Autowired
    UserService userService;
    
    @RequestMapping("/getUser")
    @ResponseBody
    public User getUserByID(@RequestParam("id") int id){
        return userService.getUserByID(id);
    }
}