Mybatis 自带分页功能，但是该分页功能是基于内存的分页，也就是会讲所有符合条件的数据查询出来，然后在从内存中获取当前页的信息，这种方式在数据量大的情况下会存在严重的性能问题。

我们通过 Mybatis-Plus 自带的分页插件可以很好的解决这个问题，实现步骤记录如下：

1、 添加配置类，示例内容如下：

package com.paratera.protect.config;

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;

/**
 * Mybatis Plus 配置类，主要用于继承分页插件
 * @author 朱治龙
 * @date 2023-10-19 23:14:00
 */
@Configuration
public class MyBatisPlusConfig {
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        // 分页插件
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        return interceptor;
    }
}

2、使用分页方法查询

2.1、selectPage

2.1.1 示例代码

    @Test
    void testSelectPage() {
        QueryWrapper<Staff> qw = Wrappers.query();
        qw.ge("age", 30);
        Page<Staff> page = new Page<Staff>(1, 2);
        // 不查记录数
//        page.setSearchCount(false);
        Page<Staff> pageData = staffMapper.selectPage(page, qw);
        System.out.println("总页数：" + pageData.getPages());
        System.out.println("总记录数：" + pageData.getTotal());
        pageData.getRecords().forEach(System.out::println);
    }

2.1.2 查询结果

DEBUG==>  Preparing: SELECT COUNT(*) AS total FROM staff WHERE (age >= ?)
DEBUG==> Parameters: 30(Integer)
TRACE<==    Columns: total
TRACE<==        Row: 4
DEBUG<==      Total: 1
DEBUG==>  Preparing: SELECT id,name,age,email,mobile,manager_id,create_time FROM staff WHERE (age >= ?) LIMIT ?
DEBUG==> Parameters: 30(Integer), 2(Long)
TRACE<==    Columns: id, name, age, email, mobile, manager_id, create_time
TRACE<==        Row: 1087982257332887553, 大boss, 40, 001@paratera.com, 13888886666, null, 2019-01-11 14:20:20
TRACE<==        Row: 1094590409767661570, 张雨琪, 31, zjq@blsc.com, 18684700070, 1088248166370832385, 2019-01-14 09:15:15
DEBUG<==      Total: 2
总页数：2
总记录数：4
Staff(id=1087982257332887553, name=大boss, age=40, email=001@paratera.com, mobile=13888886666, managerId=null, createTime=2019-01-11T14:20:20)
Staff(id=1094590409767661570, name=张雨琪, age=31, email=zjq@blsc.com, mobile=18684700070, managerId=1088248166370832385, createTime=2019-01-14T09:15:15)

2.2、selectMapsPage

2.2.1 示例代码

    @Test
    void testSelectMapsPage() {
        QueryWrapper<Staff> qw = Wrappers.query();
        qw.ge("age", 30);
        Page<Map<String, Object>> page2 = new Page<>(1, 2);
        Page<Map<String, Object>> pageData2 = staffMapper.selectMapsPage(page2, qw);

        System.out.println("总页数：" + pageData2.getPages());
        System.out.println("总记录数：" + pageData2.getTotal());
        pageData2.getRecords().forEach(System.out::println);
    }

2.2.2 查询结果

DEBUG==>  Preparing: SELECT COUNT(*) AS total FROM staff WHERE (age >= ?)
DEBUG==> Parameters: 30(Integer)
TRACE<==    Columns: total
TRACE<==        Row: 4
DEBUG<==      Total: 1
DEBUG==>  Preparing: SELECT id,name,age,email,mobile,manager_id,create_time FROM staff WHERE (age >= ?) LIMIT ?
DEBUG==> Parameters: 30(Integer), 2(Long)
TRACE<==    Columns: id, name, age, email, mobile, manager_id, create_time
TRACE<==        Row: 1087982257332887553, 大boss, 40, 001@paratera.com, 13888886666, null, 2019-01-11 14:20:20
TRACE<==        Row: 1094590409767661570, 张雨琪, 31, zjq@blsc.com, 18684700070, 1088248166370832385, 2019-01-14 09:15:15
DEBUG<==      Total: 2
总页数：2
总记录数：4
{create_time=2019-01-11T14:20:20, name=大boss, mobile=13888886666, id=1087982257332887553, age=40, email=001@paratera.com}
{create_time=2019-01-14T09:15:15, manager_id=1088248166370832385, name=张雨琪, mobile=18684700070, id=1094590409767661570, age=31, email=zjq@blsc.com}

3、附加说明

使用分页插件查询时默认是会执行两条 SQL,一条获取当前页的数据，一条获取总记录数。在某些场景下(如瀑布流模式)，只需要获取当前页的内容即可，不需要总记录数相关分页数值，此时可在创建 Page 时，第三个参数给值为 false：Page(long current, long size, boolean searchCount)。也可使用 page.setSearchCount(false);