PageHelper在springboot+mybatis框架中的使用步驟及原理解析
一、思路
將分頁(yè)所需的內(nèi)容都放到一個(gè)實(shí)體類中
分頁(yè)數(shù)據(jù)所需要的實(shí)體類!內(nèi)包含頁(yè)碼,頁(yè)大小,總條數(shù),總頁(yè)數(shù),起始行
pagehelpr提供了這個(gè)類 pageInfo,不需要我們自己創(chuàng)建
二、主要邏輯
select * from 表名 limit 起始行,展示幾條數(shù)據(jù)
#第n頁(yè) 每頁(yè)展示五條數(shù)據(jù)
select * from 表名 limit (n-1)*5,5
#每頁(yè)展示多少條 pageSize
3
#總共有多少條
total
select count(*) from 表名
#總頁(yè)數(shù)
pages
pages=total%pagesSize==0?total/pgeSize:total/pageSize+1;
#當(dāng)前頁(yè)
pageNum
三、步驟
1.引入pagehelper依賴
<dependency> <groupId>com.github.pagehelper</groupId> <artifactId>pagehelper-spring-boot-starter</artifactId> <version>1.2.5</version> </dependency>
#pagehelper分頁(yè)插件配置 pagehelper.helper-dialect=mysql pagehelper.reasonable=true pagehelper.support-methods-arguments=true pagehelper.params=count=countSql
2.bean實(shí)體類
用戶實(shí)體:
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; }
返回前端的實(shí)體類:包括查到的數(shù)據(jù)和分頁(yè)數(shù)據(jù)
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; }
2.mapper層:
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(); }
3.service層:
package com.qianfeng.service; import com.github.pagehelper.PageInfo; import com.qianfeng.bean.RegPage; public interface RegService { RegPage getAll(PageInfo pageInfo); }
4.serviceImpl:
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());//分頁(yè)后的數(shù)據(jù) long count = pageDao.getCount();//總記錄條數(shù) pageInfo.setTotal(count); //總頁(yè)數(shù) 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; } }
5.handler層:
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); } }
6.mapper.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.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>
7.application.yaml
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.* #監(jiān)控SpringBean filters: stat,wall # 底層開(kāi)啟功能,stat(sql監(jiān)控),wall(防火墻) stat-view-servlet: # 配置監(jiān)控頁(yè)功能 enabled: true login-username: admin login-password: admin resetEnable: false web-stat-filter: # 監(jiān)控web enabled: true urlPattern: /* exclusions: '*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*' filter: stat: # 對(duì)上面filters里面的stat的詳細(xì)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的配置規(guī)則 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/] # 靜態(tài)資源路徑自定義
8.application,properties
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
關(guān)于PageInfo這個(gè)類,源碼如下:
public class PageInfo implements Serializable { private static final long serialVersionUID = 1L; //當(dāng)前頁(yè) private int pageNum; //每頁(yè)的數(shù)量 private int pageSize; //當(dāng)前頁(yè)的數(shù)量 private int size; //由于startRow 和endRow 不常用,這里說(shuō)個(gè)具體的用法 //可以在頁(yè)面中"顯示startRow 到endRow 共size 條數(shù)據(jù)" //當(dāng)前頁(yè)面第一個(gè)元素在數(shù)據(jù)庫(kù)中的行號(hào) private int startRow; //當(dāng)前頁(yè)面最后一個(gè)元素在數(shù)據(jù)庫(kù)中的行號(hào) private int endRow; //總記錄數(shù) private long total; //總頁(yè)數(shù) private int pages; //結(jié)果集 private List list; //前一頁(yè) private int prePage; //下一頁(yè) private int nextPage; //是否為第一頁(yè) private boolean isFirstPage = false; //是否為最后一頁(yè) private boolean isLastPage = false; //是否有前一頁(yè) private boolean hasPreviousPage = false; //是否有下一頁(yè) private boolean hasNextPage = false; //導(dǎo)航頁(yè)碼數(shù) private int navigatePages; //所有導(dǎo)航頁(yè)號(hào) private int[] navigatepageNums; //導(dǎo)航條上的第一頁(yè) private int navigateFirstPage; //導(dǎo)航條上的最后一頁(yè) private int navigateLastPage; }
目錄結(jié)構(gòu):
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