1.引入依赖

<!--引入Mybatis-plus-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.3.2</version>
        </dependency>

2.修改application.yml 文件 ,把  mybatis 下的配置项  上级的  mybatis 名称 替换为 mybatis-plus

# MyBatis配置
mybatis-plus:
  # 搜索指定包别名
  typeAliasesPackage: com.ruoyi.**.domain
  # 配置mapper的扫描，找到所有的mapper.xml映射文件
  mapperLocations: classpath*:mapper/**/*Mapper.xml
  # 加载全局的配置文件
  configLocation: classpath:mybatis/mybatis-config.xml

3.修改mybatis的配置文件mybatis-config.xml ,加入拦截器

<plugins>
        <plugin interceptor="com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor"/>
    </plugins>

4.修改 MyBatis 配置类中的  SqlSessionFactory bean,确定bean的类型为 MybatisSqlSessionFactoryBean

@Bean
    public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception
    {
        String typeAliasesPackage = env.getProperty("mybatis-plus.typeAliasesPackage");
        String mapperLocations = env.getProperty("mybatis-plus.mapperLocations");
        String configLocation = env.getProperty("mybatis-plus.configLocation");
        typeAliasesPackage = setTypeAliasesPackage(typeAliasesPackage);
        VFS.addImplClass(SpringBootVFS.class);

        final MybatisSqlSessionFactoryBean sessionFactory = new MybatisSqlSessionFactoryBean ();
        sessionFactory.setDataSource(dataSource);
        sessionFactory.setTypeAliasesPackage(typeAliasesPackage);
        sessionFactory.setMapperLocations(resolveMapperLocations(StringUtils.split(mapperLocations, ",")));
        sessionFactory.setConfigLocation(new DefaultResourceLoader().getResource(configLocation));
        return sessionFactory.getObject();
    }

5.修改dao层接口,使其继承  BaseMapper

package com.ruoyi.coupon.mapper;

import java.util.List;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.ruoyi.coupon.domain.CouponUser;

/**
 * app用户Mapper接口
 * 
 * @author ruoyi
 * @date 2023-08-15
 */
public interface CouponUserMapper  extends BaseMapper<CouponUser>
{
}

6.修改service接口,使其继承  IService

package com.ruoyi.coupon.service;

import java.util.List;

import com.baomidou.mybatisplus.extension.service.IService;
import com.ruoyi.coupon.domain.CouponUser;

/**
 * app用户Service接口
 * 
 * @author ruoyi
 * @date 2023-08-15
 */
public interface ICouponUserService  extends IService<CouponUser>
{
}

7.修改serivice 实现类,使其继承 ServiceImpl

package com.ruoyi.coupon.service.impl;

import java.util.List;

import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.ruoyi.common.utils.DateUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.ruoyi.coupon.mapper.CouponUserMapper;
import com.ruoyi.coupon.domain.CouponUser;
import com.ruoyi.coupon.service.ICouponUserService;

/**
 * app用户Service业务层处理
 * 
 * @author ruoyi
 * @date 2023-08-15
 */
@Service
public class CouponUserServiceImpl extends ServiceImpl<CouponUserMapper, CouponUser> implements ICouponUserService
{

}