PageHelper在springboot+mybatis框架中的使用步骤及原理解析

<dependency>
    <groupId>com.github.pagehelper</groupId>
    <artifactId>pagehelper-spring-boot-starter</artifactId>
    <version>1.2.5</version>
</dependency>

#pagehelper分页插件配置
pagehelper.helper-dialect=mysql
pagehelper.reasonable=true
pagehelper.support-methods-arguments=true
pagehelper.params=count=countSql

package com.qianfeng.bean;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;
 
@Data
@ToString
@AllArgsConstructor
@NoArgsConstructor
public class Register {
    private Integer id;
 
    private String userName;
 
    private String passWord;
 
    private String rePassWord;
 
    private String idCard;
    private String gender;
 
}

package com.qianfeng.bean;
import com.github.pagehelper.PageInfo;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;
 
import java.util.List;
 
@Data
@ToString
@AllArgsConstructor
@NoArgsConstructor
public class RegPage {
    private PageInfo pageInfo;
    private List<Register> registers;
}

package com.qianfeng.mapper;
 
import com.qianfeng.bean.Register;
import org.apache.ibatis.annotations.Mapper;
 
import java.util.List;
@Mapper
public interface PageDao {
    List<Register> getAll(Integer startRow,Integer pageSize);
    long getCount();
}

package com.qianfeng.service;
 
import com.github.pagehelper.PageInfo;
import com.qianfeng.bean.RegPage;
 
public interface RegService {
    RegPage getAll(PageInfo pageInfo);
}

package com.qianfeng.service.serviceImpl;
 
import com.github.pagehelper.PageInfo;
import com.qianfeng.bean.RegPage;
import com.qianfeng.bean.Register;
import com.qianfeng.mapper.PageDao;
import com.qianfeng.service.RegService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
 
import java.util.List;
 
@Service
public class RegServiceImpl implements RegService {
    @Autowired
    private PageDao pageDao;
    @Override
    public RegPage getAll(PageInfo pageInfo) {
        List<Register> all = pageDao.getAll(pageInfo.getStartRow(), pageInfo.getPageSize());//分页后的数据
        long count = pageDao.getCount();//总记录条数
        pageInfo.setTotal(count);
        //总页数
        int pages= (int) (pageInfo.getTotal()%pageInfo.getPageSize()==0?pageInfo.getTotal()/pageInfo.getPageSize():pageInfo.getTotal()/pageInfo.getPageSize()+1);
        pageInfo.setPages(pages);
 
        RegPage regPage = new RegPage();
        regPage.setPageInfo(pageInfo);
        regPage.setRegisters(all);
        return regPage;
 
    }
}

package com.qianfeng.handler;
 
import com.github.pagehelper.PageInfo;
import com.qianfeng.bean.RegPage;
import com.qianfeng.service.RegService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
 
@RestController
public class RegHandler {
    @Autowired
    private RegService regService;
    @RequestMapping("/page/{pageNum}")
    public RegPage regPage(@PathVariable("pageNum") Integer pageNum){
        System.out.println(".........");
        PageInfo pageInfo = new PageInfo();
        pageInfo.setPageNum(pageNum);
        pageInfo.setPageSize(3);
        pageInfo.setStartRow((pageNum-1)*pageInfo.getPageSize());
        System.out.println("startRow" + pageInfo.getStartRow());
        return regService.getAll(pageInfo);
    }
}

<?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.qianfeng.mapper.PageDao">
    <select id="getAll" resultType="com.qianfeng.bean.Register">
        select * from m_register limit #{startRow},#{pageSize}
    </select>
    <select id="getCount" resultType="java.lang.Long">
        select count(*) from m_register
    </select>
</mapper>

spring:
  datasource:
    url: jdbc:mysql:///map?serverTimezone=Asia/Shanghai&useSSL=false
    username: root
    password: 123
    driver-class-name: com.mysql.jdbc.Driver
 
    druid:
      aop-patterns: com.qianfeng.*  #监控SpringBean
      filters: stat,wall     # 底层开启功能，stat（sql监控），wall（防火墙）
 
      stat-view-servlet:   # 配置监控页功能
        enabled: true
        login-username: admin
        login-password: admin
        resetEnable: false
 
      web-stat-filter:  # 监控web
        enabled: true
        urlPattern: /*
        exclusions: '*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*'
      filter:
        stat:    # 对上面filters里面的stat的详细配置
          slow-sql-millis: 1000
          logSlowSql: true
          enabled: true
        wall:
          enabled: true
          config:
            drop-table-allow: false
  mvc:
    pathmatch:
      matching-strategy: ant_path_matcher
# mybatis的配置规则
mybatis:
  #config-location: classpath:mapper/mybatis-config.xml
  mapper-locations: classpath:mapper/*
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
#      static-locations: [classpath:/haha/]  # 静态资源路径自定义

spring.main.allow-circular-references=true
spring.thymeleaf.prefix=classpath:/templates/
spring.thymeleaf.suffix=.html
pagehelper.helper-dialect=mysql
pagehelper.reasonable=true
pagehelper.support-methods-arguments=true
pagehelper.params=count=countSql

public class PageInfo implements Serializable {
private static final long serialVersionUID = 1L;
//当前页
private int pageNum;
//每页的数量
private int pageSize;
//当前页的数量
private int size;
//由于startRow 和endRow 不常用，这里说个具体的用法
//可以在页面中"显示startRow 到endRow 共size 条数据"
//当前页面第一个元素在数据库中的行号
private int startRow;
//当前页面最后一个元素在数据库中的行号
private int endRow;
//总记录数
private long total;
//总页数
private int pages;
//结果集
private List list;
//前一页
private int prePage;
//下一页
private int nextPage;
//是否为第一页
private boolean isFirstPage = false;
//是否为最后一页
private boolean isLastPage = false;
//是否有前一页
private boolean hasPreviousPage = false;
//是否有下一页
private boolean hasNextPage = false;
//导航页码数
private int navigatePages;
//所有导航页号
private int[] navigatepageNums;
//导航条上的第一页
private int navigateFirstPage;
//导航条上的最后一页
private int navigateLastPage;
}