域名解析怎么做排名做网站优化

分页是常见大型项目都需要的一个功能，PageHelper是一个非常流行的MyBatis分页插件，它支持多数据库分页，无需修改SQL语句即可实现分页功能。

本文在最后展示了两种依赖验证的结果。

一、第一种依赖方式

1、在项目中使用 PageHelper 插件需要先添加依赖：

<dependency><groupId>com.github.pagehelper</groupId><artifactId>pagehelper</artifactId><version>4.1.3</version>
</dependency>

2、这种方式需要配置一个 config 文件

package com.wen.config;import com.github.pagehelper.PageHelper;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import java.util.Properties;/*** @author : rjw* @date : 2024-09-20*/
@Configuration
public class MyBatisConfig {@Beanpublic PageHelper pageHelper() {PageHelper pageHelper = new PageHelper();Properties properties = new Properties();properties.setProperty("dialect", "Mysql");properties.setProperty("offsetAsPageNum", "true");properties.setProperty("rowBoundsWithCount", "true");pageHelper.setProperties(properties);return pageHelper;}
}

3、setProperty 方法设置了三个分页插件的属性：

• "dialect", "Mysql"：指定了数据库方言为Mysql。（主要是因为SQL语句不同）。
• "offsetAsPageNum", "true"：这个属性通常用于指定是否将传入的 offset 参数当作 pageNum （页码）使用。在这个配置中，它被设置为true，意味着如果分页查询时传递了offset（偏移量），PageHelper会将其视为页码来处理。然而，这个设置通常不是必需的，因为PageHelper默认就是使用页码（pageNum）和每页记录数（pageSize）来进行分页的。
• "rowBoundsWithCount", "true"：这个属性用于指定是否进行 count 查询以获取总记录数。在分页查询时，知道总记录数是有用的，因为它可以让你在前端展示总页数或总记录数。设置为 true 表示 PageHelper 在执行分页查询时，会先执行一个 count 查询来获取总记录数。

二、第二种依赖方式

<dependency><groupId>com.github.pagehelper</groupId><artifactId>pagehelper-spring-boot-starter</artifactId><version>1.2.10</version>
</dependency>

2、这种方式需要在配置文件配置一下，application.properties 或 application.yml 。

pagehelper.helper-dialect=mysql   // 数据库   可选
pagehelper.reasonable=true        // 规整页码范围，应对负数或过大页码
pagehelper.support-methods-arguments=true  // 规整可以通过方法参数获取，可用可不用输入即可
pagehelper.params=count=countSql

pagehelper:helper-dialect: mysqlreasonable: truesupport-methods-arguments: trueparams: count=countSql

三、创建数据库表格

3、分页条件配置

pagehelper:helper-dialect: mysqlreasonable: true   // 规整页码范围support-methods-arguments: true   // 规整方法参数获取

四、代码示例

关于统一 API 响应结果封装，代码示例在 SpringBoot 项目统一 API 响应结果封装 。

关于 mybatis 的项目搭建在 SpringBoot 项目整合 MyBatis 框架 。

1、TestController

package com.wen.controller;import com.wen.data.Result;
import com.wen.data.ResultGenerator;
import com.wen.dto.TbUser;
import com.wen.service.TestService;
import org.apache.ibatis.annotations.Param;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;@RestController
@RequestMapping("/test")
public class TestController {@Autowiredprivate TestService testService;@GetMapping("/select")public Result<?> selectUserByPage(@Param("pageSize") Integer pageSize, @Param("pageNumber") Integer pageNumber){return ResultGenerator.genSuccessResult(testService.selectUserByPage(pageSize, pageNumber));}
}

2、TestService

package com.wen.service;import com.github.pagehelper.PageInfo;
import com.wen.dto.TbUser;public interface TestService {PageInfo<TbUser> selectUserByPage(Integer pageSize, Integer pageNumber);
}

3、TestServiceImpl

package com.wen.service.impl;import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.wen.dto.TbUser;
import com.wen.mapper.TbUserMapper;
import com.wen.service.TestService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;@Service
public class TestServiceImpl implements TestService {@Autowiredprivate TbUserMapper tbUserMapper;@Overridepublic PageInfo<TbUser> selectUserByPage(Integer pageSize, Integer pageNumber) {// 这句代码要放在查询 mapper 语句的前面PageHelper.startPage(pageNumber, pageSize);List<TbUser> tbUsers = tbUserMapper.selectUser();PageInfo<TbUser> tbUserPageInfo = new PageInfo<>(tbUsers);return tbUserPageInfo;}
}

4、TbUserMapper

package com.wen.mapper;import com.wen.dto.TbUser;
import org.apache.ibatis.annotations.Mapper;
import java.util.List;@Mapper
public interface TbUserMapper {List<TbUser> selectUser();
}

5、TbUserMapper.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.wen.mapper.TbUserMapper"><select id="selectUser" resultType="com.wen.dto.TbUser">SELECT username, password FROM tb_user</select>
</mapper>

五、第一种依赖展示结果

http://localhost:8080/test/select?pageSize=5&pageNumber=1

{"code": 1,"message": "SUCCESS","data": {"pageNum": 1,"pageSize": 5,"size": 5,"orderBy": null,"startRow": 1,"endRow": 5,"total": 7,"pages": 2,"list": [{"id": 0,"username": "laowang","password": "112233"},{"id": 0,"username": "laoli","password": "123456"},{"id": 0,"username": "lisi","password": "3344"},{"id": 0,"username": "wangwu","password": "6677"},{"id": 0,"username": "周周","password": "111"}],"firstPage": 1,"prePage": 0,"nextPage": 2,"lastPage": 2,"isFirstPage": true,"isLastPage": false,"hasPreviousPage": false,"hasNextPage": true,"navigatePages": 8,"navigatepageNums": [1,2]}
}

六、第二种依赖展示结果

http://localhost:8080/test/select?pageSize=5&pageNumber=1

{"code": 1,"message": "SUCCESS","data": {"total": 7,"list": [{"id": 0,"username": "laowang","password": "112233"},{"id": 0,"username": "laoli","password": "123456"},{"id": 0,"username": "lisi","password": "3344"},{"id": 0,"username": "wangwu","password": "6677"},{"id": 0,"username": "周周","password": "111"}],"pageNum": 1,"pageSize": 5,"size": 5,"startRow": 1,"endRow": 5,"pages": 2,"prePage": 0,"nextPage": 2,"isFirstPage": true,"isLastPage": false,"hasPreviousPage": false,"hasNextPage": true,"navigatePages": 8,"navigatepageNums": [1,2],"navigateFirstPage": 1,"navigateLastPage": 2}
}