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，我们会利用Mybatis，查询数据库，得到查询结果；
（2）如果我们想利用PageHelper分页的话，其实就是，根据（1）中查到的List，对其进行处理；
（3）首先，就是设置【pageNum：当前页】和【pageSize：每页记录数】；
（4）得到Page对象；
（5）得到PageInfo对象；
（6）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 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
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 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；
package com.github.pagehelper;
import java.io.Closeable;
import java.util.ArrayList;
import java.util.List;
public class Page extends ArrayList implements Closeable {
private static final long serialVersionUID = 1L;
private int pageNum;
private int pageSize;
private int startRow;
private int endRow;
private long total;
private int pages;
private boolean count = true;
private Boolean reasonable;
private Boolean pageSizeZero;
private String countColumn;
private String orderBy;
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);
}
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 getResult() {
return this;
}
public int getPages() {
return pages;
}
public Page setPages(int pages) {
this.pages = pages;
return this;
}
public int getEndRow() {
return endRow;
}
public Page setEndRow(int endRow) {
this.endRow = endRow;
return this;
}
public int getPageNum() {
return pageNum;
}
public Page 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 setPageSize(int pageSize) {
this.pageSize = pageSize;
return this;
}
public int getStartRow() {
return startRow;
}
public Page 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 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 setPageSizeZero(Boolean pageSizeZero) {
if (pageSizeZero != null) {
this.pageSizeZero = pageSizeZero;
}
return this;
}
public String getOrderBy() {
return orderBy;
}
public Page setOrderBy(String orderBy) {
this.orderBy = orderBy;
return (Page) this;
}
public boolean isOrderByonly() {
return orderByOnly;
}
public void setOrderByonly(boolean orderByOnly) {
this.orderByonly = orderByOnly;
}
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 setCount(boolean count) {
this.count = count;
return this;
}
public Page 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;
}
public Page pageSize(int pageSize) {
this.pageSize = pageSize;
calculateStartAndEndRow();
return this;
}
public Page count(Boolean count) {
this.count = count;
return this;
}
public Page reasonable(Boolean reasonable) {
setReasonable(reasonable);
return this;
}
public Page pageSizeZero(Boolean pageSizeZero) {
setPageSizeZero(pageSizeZero);
return this;
}
public Page countColumn(String columnName) {
this.countColumn = columnName;
return this;
}
public PageInfo toPageInfo() {
PageInfo pageInfo = new PageInfo(this);
return pageInfo;
}
public PageSerializable toPageSerializable() {
PageSerializable serializable = new PageSerializable(this);
return serializable;
}
public Page doSelectPage(ISelect select) {
select.doSelect();
return (Page) this;
}
public PageInfo doSelectPageInfo(ISelect select) {
select.doSelect();
return (PageInfo) this.toPageInfo();
}
public PageSerializable doSelectPageSerializable(ISelect select) {
select.doSelect();
return (PageSerializable) 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;
}
@Override
public String toString() {
return "Page{" +
"count=" + count +
", pageNum=" + pageNum +
", pageSize=" + pageSize +
", startRow=" + startRow +
", endRow=" + endRow +
", total=" + total +
", pages=" + pages +
", reasonable=" + reasonable +
", pageSizeZero=" + pageSizeZero +
'}' + super.toString();
}
@Override
public void close() {
PageHelper.clearPage();
}
}
2.PageInfo源码；
package com.github.pagehelper;
import java.util.Collection;
import java.util.List;
@SuppressWarnings({"rawtypes", "unchecked"})
public class PageInfo extends PageSerializable {
//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() {
}
public PageInfo(List list) {
this(list, 8);
}
public PageInfo(List 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+1
if (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 PageInfo of(List list) {
return new PageInfo(list);
}
public static PageInfo of(List list, int navigatePages) {
return new PageInfo(list, navigatePages);
}
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++;
}
}
}
}
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;
}
}
}
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;
}
@Override
public 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();
}
}
1.Page源码；
package com.github.pagehelper;
import java.io.Closeable;
import java.util.ArrayList;
import java.util.List;
public class Page extends ArrayList implements Closeable {
private static final long serialVersionUID = 1L;
private int pageNum;
private int pageSize;
private int startRow;
private int endRow;
private long total;
private int pages;
private boolean count = true;
private Boolean reasonable;
private Boolean pageSizeZero;
private String countColumn;
private String orderBy;
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);
}
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 getResult() {
return this;
}
public int getPages() {
return pages;
}
public Page setPages(int pages) {
this.pages = pages;
return this;
}
public int getEndRow() {
return endRow;
}
public Page setEndRow(int endRow) {
this.endRow = endRow;
return this;
}
public int getPageNum() {
return pageNum;
}
public Page 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 setPageSize(int pageSize) {
this.pageSize = pageSize;
return this;
}
public int getStartRow() {
return startRow;
}
public Page 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 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 setPageSizeZero(Boolean pageSizeZero) {
if (pageSizeZero != null) {
this.pageSizeZero = pageSizeZero;
}
return this;
}
public String getOrderBy() {
return orderBy;
}
public Page setOrderBy(String orderBy) {
this.orderBy = orderBy;
return (Page) this;
}
public boolean isOrderByonly() {
return orderByOnly;
}
public void setOrderByonly(boolean orderByOnly) {
this.orderByonly = orderByOnly;
}
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 setCount(boolean count) {
this.count = count;
return this;
}
public Page 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;
}
public Page pageSize(int pageSize) {
this.pageSize = pageSize;
calculateStartAndEndRow();
return this;
}
public Page count(Boolean count) {
this.count = count;
return this;
}
public Page reasonable(Boolean reasonable) {
setReasonable(reasonable);
return this;
}
public Page pageSizeZero(Boolean pageSizeZero) {
setPageSizeZero(pageSizeZero);
return this;
}
public Page countColumn(String columnName) {
this.countColumn = columnName;
return this;
}
public PageInfo toPageInfo() {
PageInfo pageInfo = new PageInfo(this);
return pageInfo;
}
public PageSerializable toPageSerializable() {
PageSerializable serializable = new PageSerializable(this);
return serializable;
}
public Page doSelectPage(ISelect select) {
select.doSelect();
return (Page) this;
}
public PageInfo doSelectPageInfo(ISelect select) {
select.doSelect();
return (PageInfo) this.toPageInfo();
}
public PageSerializable doSelectPageSerializable(ISelect select) {
select.doSelect();
return (PageSerializable) 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;
}
@Override
public String toString() {
return "Page{" +
"count=" + count +
", pageNum=" + pageNum +
", pageSize=" + pageSize +
", startRow=" + startRow +
", endRow=" + endRow +
", total=" + total +
", pages=" + pages +
", reasonable=" + reasonable +
", pageSizeZero=" + pageSizeZero +
'}' + super.toString();
}
@Override
public void close() {
PageHelper.clearPage();
}
}
2.PageInfo源码；
package com.github.pagehelper;
import java.util.Collection;
import java.util.List;
@SuppressWarnings({"rawtypes", "unchecked"})
public class PageInfo extends PageSerializable {
//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() {
}
public PageInfo(List list) {
this(list, 8);
}
public PageInfo(List 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+1
if (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 PageInfo of(List list) {
return new PageInfo(list);
}
public static PageInfo of(List list, int navigatePages) {
return new PageInfo(list, navigatePages);
}
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++;
}
}
}
}
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;
}
}
}
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;
}
@Override
public 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，我们会利用Mybatis，查询数据库，得到查询结果；
（2）如果我们想利用PageHelper分页的话，其实就是，根据（1）中查到的List，对其进行处理；
我们对（1）中查询到的List，对其进行处理；也就是说，在（1）中List的基础上，包装得到Page或者PageInfo对象；
（3）首先，就是设置【pageNum：当前页】和【pageSize：每页记录数】；
（4）得到Page对象；
（5）得到PageInfo对象；
（6）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；
（1）首先，我们会利用Mybatis，查询数据库，得到查询结果；
（2）如果我们想利用PageHelper分页的话，其实就是，根据（1）中查到的List，对其进行处理；
我们对（1）中查询到的List，对其进行处理；也就是说，在（1）中List的基础上，包装得到Page或者PageInfo对象；
（3）首先，就是设置【pageNum：当前页】和【pageSize：每页记录数】；
（4）得到Page对象；
（5）得到PageInfo对象；
（6）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；
