一、导入依赖

<!-- MyBatis-plus的依赖 -->
<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.4</version>
</dependency>

<!-- mysql的依赖 -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
</dependency>

<!-- spring-test 测试依赖 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
</dependency>

<!-- lombok -->
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
</dependency>

二、指定要扫描mapper所在的包（或者在mapper类上加上@mappper注解）

 代码如下：

// 指定mapper所在包
@MapperScan(basePackages = "org.xxx.mapper")
@SpringBootApplication
public class Application {
    public static void main( String[] args ) {
        SpringApplication.run(Application.class,args);
    }
}

三、分页查询

 方式一：使用 selectPage 进行分页

   ① 配置MyBatisPlus的拦截器

import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MybatisPlusConfig {

    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor(){
        // 1. 创建 Mybatis-plus 的拦截器
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        // 2. 指定要对分页操作进行拦截，指定数据库的类型为 Mysql
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        return interceptor;
    }
}

   ②  进行分页查询

import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.github.pagehelper.PageHelper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.xxx.pojo.Player;
import java.util.List;

@SpringBootTest
class PlayerMapperTest {

    @Autowired
    private PlayerMapper playerMapper;

    @Test
    public void test_selectPage(){
        //  页码
        int page = 5;
        //  每一页的数据量
        int pageSize = 5;   
        
        //  分页查询    null代表不指定查询条件
        Page<Player> playerPage = playerMapper.selectPage(new Page<>(page, pageSize), null);
        //  拿到查询结果  并输出打印
        List<Player> players = playerPage.getRecords();
        System.out.println(players);
    }
}

方式二：使用 PageHelper 开启分页

  导入PageHelper依赖

<dependency>
    <groupId>com.github.pagehelper</groupId>
    <artifactId>pagehelper-spring-boot-starter</artifactId>
    <version>1.4.6</version>
</dependency>

进行分页查询

 ① 利用 PageHelper.startPage(页码，每一页的数据量) 开启分页

   如果利用 PageHelper.startPage() 开启了分页查询，那么selectList()本质上返回的是分页对象 （List的子类），

  不然selectList查询出的结果就是普通的List类

 ② 通过 selectList(查询条件) 直接查询

import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.github.pagehelper.PageHelper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.xxx.pojo.Player;
import java.util.List;

@SpringBootTest
class PlayerMapperTest {

    @Autowired
    private PlayerMapper playerMapper;

    @Test
    public void test_page(){
        //  页码
        int page = 5;
        //  每一页的数据量
        int pageSize = 5;   
        
        //	开启分页查询
        PageHelper.startPage(page,pageSize);
        //	查询并打印结果
        List<Player> players = playerMapper.selectList(null);
        System.out.println(players);
    }
}