本地开发环境说明

开发依赖	版本
Spring Boot	3.0.6
Mybatis-Plus	3.5.3.1
JDK	20

pom.xml主要依赖

    <dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
    </dependency>
    <!-- 根据需要修改数据库 -->
    <dependency>
        <groupId>com.h2database</groupId>
        <artifactId>h2</artifactId>
    </dependency>
</dependencies>

application.yml主要配置

debug: true
logging:
  level:
    root: debug

spring:
  datasource:
    driver-class-name: org.h2.Driver
    url: jdbc:h2:tcp://localhost/D:/ProgramFiles/h2database/data/test;MODE=MYSQL;
    username:
    password:

mybatis-plus:
  # 所有实体类所在包路径
  type-aliases-package: com.wen3.**.po
  # mapper.xmml文件路径，多个使用逗号分隔
  mapper-locations: classpath*:resources/mapper/*.xml
  configuration:
    log-impl: org.apache.ibatis.logging.slf4j.Slf4jImpl

@MapperScan注解使用说明

@MapperScan注解的作用是用来指定Mapper接口的位置，示例如下

@MapperScan(basePackages = "com.wen3.demo.mybatisplus.dao")
@SpringBootApplication
public class DemoMybatisplusApplication {

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

basePackages一定要指定Mapper接口的包路径，启动的时候Mybatis-Plus会把这个包及子包下的所有接口当做Mapper
比如basePackages的值指定为com.wen3，则会把Service接口也当做Mapper，在调用方法的时候就会报错org.apache.ibatis.binding.BindingException: Invalid bound statement (not found)

实体类示例

package com.wen3.demo.mybatisplus.po;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Getter;
import lombok.Setter;
import lombok.experimental.Accessors;

/**
 * <p>
 * 
 * </p>
 *
 * @author tangheng
 * @since 2023-05-21
 */
@Getter
@Setter
@Accessors(chain = true)
@TableName("USER")
public class UserPo {

    /**
     * 用户id
     */
    @TableId(value = "USER_ID", type = IdType.AUTO)
    private String userId;

    /**
     * 用户姓名
     */
    @TableField("USER_NAME")
    private String userName;

    /**
     * 用户性别
     */
    @TableField("USER_SEX")
    private String userSex;

    /**
     * 用户邮箱
     */
    @TableField("USER_EMAIL")
    private String userEmail;

    /**
     * 用户账号
     */
    @TableField("USER_ACCOUNT")
    private String userAccount;

    /**
     * 用户地址
     */
    @TableField("USER_ADDRESS")
    private String userAddress;

    /**
     * 用户密码
     */
    @TableField("USER_PASSWORD")
    private String userPassword;

    /**
     * 用户城市
     */
    @TableField("USER_CITY")
    private String userCity;

    /**
     * 用户状态
     */
    @TableField("USER_STATUS")
    private Integer userStatus;

    /**
     * 用户区县
     */
    @TableField("USER_SEAT")
    private String userSeat;
}

Mapper接口示例

package com.wen3.demo.mybatisplus.dao;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.wen3.demo.mybatisplus.po.UserPo;

import java.util.Map;

public interface UserMapper extends BaseMapper<UserPo> {

}

Service接口示例

package com.wen3.demo.mybatisplus.service;

import com.wen3.demo.mybatisplus.po.UserPo;

import java.util.Map;

public interface UserService {

    UserPo getById(String userId);
}

Service接口实现类示例

package com.wen3.demo.mybatisplus.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.wen3.demo.mybatisplus.po.UserPo;
import com.wen3.demo.mybatisplus.dao.UserMapper;
import com.wen3.demo.mybatisplus.service.UserService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import org.springframework.stereotype.Service;

import java.util.Map;

@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, UserPo> implements UserService {

    @Override
    public UserPo getById(String userId) {
        LambdaQueryWrapper<UserPo> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.eq(UserPo::getUserId, userId);
        return baseMapper.selectOne(queryWrapper);
    }
}

单元测试示例

package com.wen3.demo.mybatisplus.service;

import com.wen3.demo.mybatisplus.MybatisPlusSpringbootTestBase;
import com.wen3.demo.mybatisplus.po.UserPo;
import jakarta.annotation.Resource;
import org.junit.jupiter.api.Test;

import java.util.Map;

import static org.junit.jupiter.api.Assertions.*;

class UserServiceTest extends MybatisPlusSpringbootTestBase {

    @Resource
    private UserService userService;

    @Test
    void getById() {
        String userId = "U11902a8436094248a45dd3821b07e82a1651108484889";
        UserPo testResult = userService.getById(userId);
        log.info("testResult: {}", testResult);
    }
}

打印SQL日志

mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

加上这段配置后，SQL的日志确实是输出了，在控制台可以看到

StdOutImpl源码是使用System.out或System.err来打印SQL的
SpringBoot默认使用logback日志组件，我们可以使用Mybatis-Plus提供的slf4j实现

使用slf4j打印SQL

mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.slf4j.Slf4jImpl

重启后日志没打印出来，连控制台也没有输出SQL日志
使用slf4j后，日志输出级别就由SpringBoot接管了，SpringBoot默认是INFO级别
修改Mybatis-Plus下的日志为DEBUG，比如: logging.level.com.baomidou.mybatisplus=DEBUG
重启后就能看到日志了