SpringBoot实现条件分页

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一、概述

当查询后返回的数据很多时，为了提高查询效率，需使用条件分页

二、使用步骤

pom.xml导入pageHelper坐标

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

创建实体类PageBean

pojo/PageBean.java

package com.itheima.pojo;import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;import java.util.List;//分页返回结果对象
@Data
@NoArgsConstructor
@AllArgsConstructor
public class PageBean <T>{private Long total;//总条数private List<T> items;//当前页数据集合
}

控制层增加分页查询接口

controller/ArticleController.java

//分页查询
@GetMapping
public Result<PageBean<Article>> list(Integer pageNum,Integer pageSize,@RequestParam(required = false) Integer categoryId,@RequestParam(required = false) String state
){PageBean<Article> pb = articleService.list(pageNum,pageSize,categoryId,state);return Result.success(pb);
}

服务层编写业务逻辑

service/ArticleService.java

//条件分页列表查询
PageBean<Article> list(Integer pageNum, Integer pageSize, Integer categoryId, String state);

service/impl/ArticleServiceImpl.java

//分页查询
@Override
public PageBean<Article> list(Integer pageNum, Integer pageSize, Integer categoryId, String state) {//创建PageBean对象PageBean<Article> pb = new PageBean<>();//开启分页查询pageHelperPageHelper.startPage(pageNum,pageSize);//调用mapper// 获取用户idMap<String, Object> map = ThreadLocalUtil.get();Integer userId = (Integer) map.get("id");List<Article> as = articleMapper.list(userId,categoryId,state);//Page中提供了方法，可以获取PageHelper分页查询后得到的总记录条数和分页结果Page<Article> p = (Page<Article>) as;//把数据填充到PageBean中pb.setTotal(p.getTotal());pb.setItems(p.getResult());return pb;
}

准备映射配置文件

resources/com/itheima/mapper/ArticleMapper.xml(目录结构要与src中mapper层的目录结构一致）

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itheima.mapper.ArticleMapper"><!--动态sql--><select id="list" resultType="com.itheima.pojo.Article">select * from article<where><if test="categoryId != null">category_id = #{categoryId}</if><if test="state != null">and state = #{state}</if>and create_user = #{userId}</where></select>
</mapper>

数据层

mapper/ArticleMapper.java

//分页查询
List<Article> list(Integer userId, Integer categoryId, String state);

三、参考资料

https://www.bilibili.com/video/BV14z4y1N7pg?spm_id_from=333.788.player.switch&vd_source=0467ab39cc5ec5940fee22a0e7797575&p=35