说明：

（1）为什么写本篇博客？：

          ● 在【Spring Boot电商项目29：商品分类模块八：后台的【分类列表（平铺）】接口；】中，实现分页功能时，使用到了PageHelper分页插件；

          ● 但是，在【Spring Boot电商项目29：商品分类模块八：后台的【分类列表（平铺）】接口；】中，我们使用的是PageHelper中的PageInfo对象；

          ● 而，在【MyBatis进阶五：PageHelper分页插件；】中，我们第一次遇到PageHelper时候，使用的是PageHelper中的Page对象；

          ● 所以，本篇博客，就分析一下：PageHelper分页插件中的：Page和PageInfo的区别；

（2）本篇博客参考的博客有：

          ● 【Page和PageInfo】，该文的作者是【程序员^晓洋】；

目录

一：Page和PageInfo；（这儿，归纳了两个对象的属性，总结的不错；）

1. Page和PageInfo简介；

2.Page和PageInfo，具体属性分析；

二：Page和PageInfo：源码；（这部分，仅供参考，爱看不看）

1.Page源码；

2.PageInfo源码；

三：Page和PageInfo：使用；（重要！）

（1）首先，就是开启分页，设置【pageNum：当前页】和【pageSize：每页记录数】；

 （2）然后，我们会利用Mybatis，根据上面设置的分页条件，去查询数据库，得到查询结果；

（3）然后，可以根据前端对分页数据格式的要求，可以把（3）中查到的分页数据，包装成Page对象；

（4）或者，包装成PageInfo对象；

（5）使用Page对象还是使用PageInfo对象？

---

一：Page和PageInfo；（这儿，归纳了两个对象的属性，总结的不错；）

这儿的内容，完全照抄自【Page和PageInfo】，该文的作者是【程序员^晓洋】；

1. Page和PageInfo简介；

两者都能获取到数据，

Page是一个ArrayListList。

PageInfo是一个对象，能获取到的数据比Page多；

2.Page和PageInfo，具体属性分析；

Page对象：

private int pageNum;	//当前页码
private int pageSize; 	//每页数据的数量
private int startRow;	//始页首行行号
private int endRow;		//尾页尾行行号
private long total;		//总记录数
private int pages;		//总页数
private Boolean reasonable; //分页合理化
private Boolean pageSizeZero; //当设置为true的时候，如果pagesize设置为0（或RowBounds的limit=0），就不执行分页，返回全部结果

PageInfo对象：

    private int pageNum;   			//当前页private int pageSize;			//每页显示数据条数private int size;				//当前页的数量private int startRow; 			//始页首行行号private int endRow;				//尾页尾行行号private long total;				//总记录数private int pages;				//总页数private List<T> list;			//查询结果的数据private int firstPage;			//首页private int prePage;			//上一页private int nextPage;			// 下一页private int lastPage;			//最后一页private boolean isFirstPage;	//是不是第一页private boolean isLastPage;		//是不是最后一页private boolean hasPreviousPage;//有没有上一页private boolean hasNextPage;	//有没有下一页private int navigatePages;		//所有导航页号private int[] navigatepageNums;	//导航页码数

---

二：Page和PageInfo：源码；（这部分，仅供参考，爱看不看）

1.Page源码；

/** The MIT License (MIT)** Copyright (c) 2014-2017 abel533@gmail.com** Permission is hereby granted, free of charge, to any person obtaining a copy* of this software and associated documentation files (the "Software"), to deal* in the Software without restriction, including without limitation the rights* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell* copies of the Software, and to permit persons to whom the Software is* furnished to do so, subject to the following conditions:** The above copyright notice and this permission notice shall be included in* all copies or substantial portions of the Software.** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN* THE SOFTWARE.*/package com.github.pagehelper;import java.io.Closeable;
import java.util.ArrayList;
import java.util.List;/*** Mybatis - 分页对象** @author liuzh/abel533/isea533* @version 3.6.0*          项目地址 : http://git.oschina.net/free/Mybatis_PageHelper*/
public class Page<E> extends ArrayList<E> implements Closeable {private static final long serialVersionUID = 1L;/*** 页码，从1开始*/private int pageNum;/*** 页面大小*/private int pageSize;/*** 起始行*/private int startRow;/*** 末行*/private int endRow;/*** 总数*/private long total;/*** 总页数*/private int pages;/*** 包含count查询*/private boolean count = true;/*** 分页合理化*/private Boolean reasonable;/*** 当设置为true的时候，如果pagesize设置为0（或RowBounds的limit=0），就不执行分页，返回全部结果*/private Boolean pageSizeZero;/*** 进行count查询的列名*/private String countColumn;/*** 排序*/private String orderBy;/*** 只增加排序*/private boolean orderByOnly;public Page() {super();}public Page(int pageNum, int pageSize) {this(pageNum, pageSize, true, null);}public Page(int pageNum, int pageSize, boolean count) {this(pageNum, pageSize, count, null);}private Page(int pageNum, int pageSize, boolean count, Boolean reasonable) {super(0);if (pageNum == 1 && pageSize == Integer.MAX_VALUE) {pageSizeZero = true;pageSize = 0;}this.pageNum = pageNum;this.pageSize = pageSize;this.count = count;calculateStartAndEndRow();setReasonable(reasonable);}/*** int[] rowBounds* 0 : offset* 1 : limit*/public Page(int[] rowBounds, boolean count) {super(0);if (rowBounds[0] == 0 && rowBounds[1] == Integer.MAX_VALUE) {pageSizeZero = true;this.pageSize = 0;} else {this.pageSize = rowBounds[1];this.pageNum = rowBounds[1] != 0 ? (int) (Math.ceil(((double) rowBounds[0] + rowBounds[1]) / rowBounds[1])) : 0;}this.startRow = rowBounds[0];this.count = count;this.endRow = this.startRow + rowBounds[1];}public List<E> getResult() {return this;}public int getPages() {return pages;}public Page<E> setPages(int pages) {this.pages = pages;return this;}public int getEndRow() {return endRow;}public Page<E> setEndRow(int endRow) {this.endRow = endRow;return this;}public int getPageNum() {return pageNum;}public Page<E> setPageNum(int pageNum) {//分页合理化，针对不合理的页码自动处理this.pageNum = ((reasonable != null && reasonable) && pageNum <= 0) ? 1 : pageNum;return this;}public int getPageSize() {return pageSize;}public Page<E> setPageSize(int pageSize) {this.pageSize = pageSize;return this;}public int getStartRow() {return startRow;}public Page<E> setStartRow(int startRow) {this.startRow = startRow;return this;}public long getTotal() {return total;}public void setTotal(long total) {this.total = total;if (total == -1) {pages = 1;return;}if (pageSize > 0) {pages = (int) (total / pageSize + ((total % pageSize == 0) ? 0 : 1));} else {pages = 0;}//分页合理化，针对不合理的页码自动处理if ((reasonable != null && reasonable) && pageNum > pages) {if(pages!=0){pageNum = pages;}calculateStartAndEndRow();}}public Boolean getReasonable() {return reasonable;}public Page<E> setReasonable(Boolean reasonable) {if (reasonable == null) {return this;}this.reasonable = reasonable;//分页合理化，针对不合理的页码自动处理if (this.reasonable && this.pageNum <= 0) {this.pageNum = 1;calculateStartAndEndRow();}return this;}public Boolean getPageSizeZero() {return pageSizeZero;}public Page<E> setPageSizeZero(Boolean pageSizeZero) {if (pageSizeZero != null) {this.pageSizeZero = pageSizeZero;}return this;}public String getOrderBy() {return orderBy;}public <E> Page<E> setOrderBy(String orderBy) {this.orderBy = orderBy;return (Page<E>) this;}public boolean isOrderByOnly() {return orderByOnly;}public void setOrderByOnly(boolean orderByOnly) {this.orderByOnly = orderByOnly;}/*** 计算起止行号*/private void calculateStartAndEndRow() {this.startRow = this.pageNum > 0 ? (this.pageNum - 1) * this.pageSize : 0;this.endRow = this.startRow + this.pageSize * (this.pageNum > 0 ? 1 : 0);}public boolean isCount() {return this.count;}public Page<E> setCount(boolean count) {this.count = count;return this;}/*** 设置页码** @param pageNum* @return*/public Page<E> pageNum(int pageNum) {//分页合理化，针对不合理的页码自动处理this.pageNum = ((reasonable != null && reasonable) && pageNum <= 0) ? 1 : pageNum;return this;}/*** 设置页面大小** @param pageSize* @return*/public Page<E> pageSize(int pageSize) {this.pageSize = pageSize;calculateStartAndEndRow();return this;}/*** 是否执行count查询** @param count* @return*/public Page<E> count(Boolean count) {this.count = count;return this;}/*** 设置合理化** @param reasonable* @return*/public Page<E> reasonable(Boolean reasonable) {setReasonable(reasonable);return this;}/*** 当设置为true的时候，如果pagesize设置为0（或RowBounds的limit=0），就不执行分页，返回全部结果** @param pageSizeZero* @return*/public Page<E> pageSizeZero(Boolean pageSizeZero) {setPageSizeZero(pageSizeZero);return this;}/*** 指定 count 查询列** @param columnName* @return*/public Page<E> countColumn(String columnName) {this.countColumn = columnName;return this;}public PageInfo<E> toPageInfo() {PageInfo<E> pageInfo = new PageInfo<E>(this);return pageInfo;}public PageSerializable<E> toPageSerializable() {PageSerializable<E> serializable = new PageSerializable<E>(this);return serializable;}public <E> Page<E> doSelectPage(ISelect select) {select.doSelect();return (Page<E>) this;}public <E> PageInfo<E> doSelectPageInfo(ISelect select) {select.doSelect();return (PageInfo<E>) this.toPageInfo();}public <E> PageSerializable<E> doSelectPageSerializable(ISelect select) {select.doSelect();return (PageSerializable<E>) this.toPageSerializable();}public long doCount(ISelect select) {this.pageSizeZero = true;this.pageSize = 0;select.doSelect();return this.total;}public String getCountColumn() {return countColumn;}public void setCountColumn(String countColumn) {this.countColumn = countColumn;}@Overridepublic String toString() {return "Page{" +"count=" + count +", pageNum=" + pageNum +", pageSize=" + pageSize +", startRow=" + startRow +", endRow=" + endRow +", total=" + total +", pages=" + pages +", reasonable=" + reasonable +", pageSizeZero=" + pageSizeZero +'}' + super.toString();}@Overridepublic void close() {PageHelper.clearPage();}
}

2.PageInfo源码；

/** The MIT License (MIT)** Copyright (c) 2014-2017 abel533@gmail.com** Permission is hereby granted, free of charge, to any person obtaining a copy* of this software and associated documentation files (the "Software"), to deal* in the Software without restriction, including without limitation the rights* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell* copies of the Software, and to permit persons to whom the Software is* furnished to do so, subject to the following conditions:** The above copyright notice and this permission notice shall be included in* all copies or substantial portions of the Software.** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN* THE SOFTWARE.*/package com.github.pagehelper;import java.util.Collection;
import java.util.List;/*** 对Page<E>结果进行包装* <p/>* 新增分页的多项属性，主要参考:http://bbs.csdn.net/topics/360010907** @author liuzh/abel533/isea533* @version 3.3.0* @since 3.2.2* 项目地址 : http://git.oschina.net/free/Mybatis_PageHelper*/
@SuppressWarnings({"rawtypes", "unchecked"})
public class PageInfo<T> extends PageSerializable<T> {//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;//总页数private int pages;//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;public PageInfo() {}/*** 包装Page对象** @param list*/public PageInfo(List<T> list) {this(list, 8);}/*** 包装Page对象** @param list          page结果* @param navigatePages 页码数量*/public PageInfo(List<T> list, int navigatePages) {super(list);if (list instanceof Page) {Page page = (Page) list;this.pageNum = page.getPageNum();this.pageSize = page.getPageSize();this.pages = page.getPages();this.size = page.size();//由于结果是>startRow的，所以实际的需要+1if (this.size == 0) {this.startRow = 0;this.endRow = 0;} else {this.startRow = page.getStartRow() + 1;//计算实际的endRow（最后一页的时候特殊）this.endRow = this.startRow - 1 + this.size;}} else if (list instanceof Collection) {this.pageNum = 1;this.pageSize = list.size();this.pages = this.pageSize > 0 ? 1 : 0;this.size = list.size();this.startRow = 0;this.endRow = list.size() > 0 ? list.size() - 1 : 0;}if (list instanceof Collection) {this.navigatePages = navigatePages;//计算导航页calcNavigatepageNums();//计算前后页，第一页，最后一页calcPage();//判断页面边界judgePageBoudary();}}public static <T> PageInfo<T> of(List<T> list) {return new PageInfo<T>(list);}public static <T> PageInfo<T> of(List<T> list, int navigatePages) {return new PageInfo<T>(list, navigatePages);}/*** 计算导航页*/private void calcNavigatepageNums() {//当总页数小于或等于导航页码数时if (pages <= navigatePages) {navigatepageNums = new int[pages];for (int i = 0; i < pages; i++) {navigatepageNums[i] = i + 1;}} else { //当总页数大于导航页码数时navigatepageNums = new int[navigatePages];int startNum = pageNum - navigatePages / 2;int endNum = pageNum + navigatePages / 2;if (startNum < 1) {startNum = 1;//(最前navigatePages页for (int i = 0; i < navigatePages; i++) {navigatepageNums[i] = startNum++;}} else if (endNum > pages) {endNum = pages;//最后navigatePages页for (int i = navigatePages - 1; i >= 0; i--) {navigatepageNums[i] = endNum--;}} else {//所有中间页for (int i = 0; i < navigatePages; i++) {navigatepageNums[i] = startNum++;}}}}/*** 计算前后页，第一页，最后一页*/private void calcPage() {if (navigatepageNums != null && navigatepageNums.length > 0) {navigateFirstPage = navigatepageNums[0];navigateLastPage = navigatepageNums[navigatepageNums.length - 1];if (pageNum > 1) {prePage = pageNum - 1;}if (pageNum < pages) {nextPage = pageNum + 1;}}}/*** 判定页面边界*/private void judgePageBoudary() {isFirstPage = pageNum == 1;isLastPage = pageNum == pages || pages == 0;hasPreviousPage = pageNum > 1;hasNextPage = pageNum < pages;}public int getPageNum() {return pageNum;}public void setPageNum(int pageNum) {this.pageNum = pageNum;}public int getPageSize() {return pageSize;}public void setPageSize(int pageSize) {this.pageSize = pageSize;}public int getSize() {return size;}public void setSize(int size) {this.size = size;}public int getStartRow() {return startRow;}public void setStartRow(int startRow) {this.startRow = startRow;}public int getEndRow() {return endRow;}public void setEndRow(int endRow) {this.endRow = endRow;}public int getPages() {return pages;}public void setPages(int pages) {this.pages = pages;}public int getPrePage() {return prePage;}public void setPrePage(int prePage) {this.prePage = prePage;}public int getNextPage() {return nextPage;}public void setNextPage(int nextPage) {this.nextPage = nextPage;}public boolean isIsFirstPage() {return isFirstPage;}public void setIsFirstPage(boolean isFirstPage) {this.isFirstPage = isFirstPage;}public boolean isIsLastPage() {return isLastPage;}public void setIsLastPage(boolean isLastPage) {this.isLastPage = isLastPage;}public boolean isHasPreviousPage() {return hasPreviousPage;}public void setHasPreviousPage(boolean hasPreviousPage) {this.hasPreviousPage = hasPreviousPage;}public boolean isHasNextPage() {return hasNextPage;}public void setHasNextPage(boolean hasNextPage) {this.hasNextPage = hasNextPage;}public int getNavigatePages() {return navigatePages;}public void setNavigatePages(int navigatePages) {this.navigatePages = navigatePages;}public int[] getNavigatepageNums() {return navigatepageNums;}public void setNavigatepageNums(int[] navigatepageNums) {this.navigatepageNums = navigatepageNums;}public int getNavigateFirstPage() {return navigateFirstPage;}public int getNavigateLastPage() {return navigateLastPage;}public void setNavigateFirstPage(int navigateFirstPage) {this.navigateFirstPage = navigateFirstPage;}public void setNavigateLastPage(int navigateLastPage) {this.navigateLastPage = navigateLastPage;}@Overridepublic String toString() {final StringBuilder sb = new StringBuilder("PageInfo{");sb.append("pageNum=").append(pageNum);sb.append(", pageSize=").append(pageSize);sb.append(", size=").append(size);sb.append(", startRow=").append(startRow);sb.append(", endRow=").append(endRow);sb.append(", total=").append(total);sb.append(", pages=").append(pages);sb.append(", list=").append(list);sb.append(", prePage=").append(prePage);sb.append(", nextPage=").append(nextPage);sb.append(", isFirstPage=").append(isFirstPage);sb.append(", isLastPage=").append(isLastPage);sb.append(", hasPreviousPage=").append(hasPreviousPage);sb.append(", hasNextPage=").append(hasNextPage);sb.append(", navigatePages=").append(navigatePages);sb.append(", navigateFirstPage=").append(navigateFirstPage);sb.append(", navigateLastPage=").append(navigateLastPage);sb.append(", navigatepageNums=");if (navigatepageNums == null) {sb.append("null");} else {sb.append('[');for (int i = 0; i < navigatepageNums.length; ++i) {sb.append(i == 0 ? "" : ", ").append(navigatepageNums[i]);}sb.append(']');}sb.append('}');return sb.toString();}
}

---

三：Page和PageInfo：使用；（重要！）

（1）首先，就是开启分页，设置【pageNum：当前页】和【pageSize：每页记录数】；

 （2）然后，我们会利用Mybatis，根据上面设置的分页条件，去查询数据库，得到查询结果；

（3）然后，可以根据前端对分页数据格式的要求，可以把（3）中查到的分页数据，包装成Page对象；

（4）或者，包装成PageInfo对象；

（5）使用Page对象还是使用PageInfo对象？

          ● 目前的个人理解：使用Page对象还是PageInfo对象，需要根据前端的要求，或者说是根据接口对返回数据的格式的要求；

          ● 比如，在【Spring Boot电商项目29：商品分类模块八：后台的【分类列表（平铺）】接口；】中，【分类列表（平铺）接口】的接口文档要求，接口的返回是：

所以，对于这样的接口要求，很自然就是使用PageInfo对象；