1.PageHelper的引用

pom.xml文件引用

<!-- pagehelper :分页插件 -->
<dependency><groupId>com.github.pagehelper</groupId><artifactId>pagehelper</artifactId><version>5.1.2</version>
</dependency>
<!-- pagehelper的依赖包:jsqlparser -->
<dependency><groupId>com.github.jsqlparser</groupId><artifactId>jsqlparser</artifactId><version>0.9.5</version>
</dependency>

<!--  Springboot的PageHelper的启动器 --><dependency><groupId>com.github.pagehelper</groupId><artifactId>pagehelper-spring-boot-starter</artifactId><version>1.2.3</version>
</dependency>

2.封装PageInfo类

/** 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.Serializable;
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> 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<T> 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;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) {if (list instanceof Page) {Page page = (Page) list;this.pageNum = page.getPageNum();this.pageSize = page.getPageSize();this.pages = page.getPages();this.list = page;this.size = page.size();this.total = page.getTotal();//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.list = list;this.size = list.size();this.total = 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();}}/*** 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 long getTotal() {return total;}public void setTotal(long total) {this.total = total;}public int getPages() {return pages;}public void setPages(int pages) {this.pages = pages;}public List<T> getList() {return list;}public void setList(List<T> list) {this.list = list;}@Deprecated// firstPage就是1, 此函数获取的是导航条上的第一页, 容易产生歧义public int getFirstPage() {return navigateFirstPage;}@Deprecatedpublic void setFirstPage(int firstPage) {this.navigateFirstPage = firstPage;}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;}@Deprecated// 请用getPages()来获取最后一页, 此函数获取的是导航条上的最后一页, 容易产生歧义.public int getLastPage() {return navigateLastPage;}@Deprecatedpublic void setLastPage(int lastPage) {this.navigateLastPage = lastPage;}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 StringBuffer sb = new StringBuffer("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();}
}

3.实例

 public PageResult<Brand> queryBrandsByPage(String key, Integer page, Integer rows, String sortBy, boolean desc) {//根据name模糊查询，或者首字母查询Example example = new Example(Brand.class);Example.Criteria criteria = example.createCriteria();if (StringUtils.isEmpty(key)){//模糊查询名字，或者按首字母查询criteria.andLike("name", "%" + key + "%").orEqualTo("letter",key);}//添加分页条件PageHelper.startPage(page,rows);//添加排序条件//首先判断有没有排序字段if (StringUtils.isNotBlank(sortBy)){example.setOrderByClause(sortBy+ " " + (desc ? "desc" : "asc"));}List<Brand> brands = this.brandMapper.selectByExample(example);//先包装成pageInfo对象PageInfo<Brand> pageInfo = new PageInfo<>(brands);//包装成分页结果集返回//pageInfo//总记录数//private long total;//结果集//private List<T> list;return new PageResult<>(pageInfo.getTotal(),pageInfo.getList());}

pageInfo.getTotal() 总记录数
在真正使用时, 会发现total的值并不等于数据库中记录总数, 并且该值永远等于查询页的记录数, 即getTotal和getSize()效果相同. 读者若自行查看SQL日志, 可发现startPage()方法成功执行, 返回的List是符合查询条件的。
pageInfo.getList()返回的是一个结果集

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PageHelper的PageInfo使用方法

自定义标题

1.PageHelper的引用

2.封装PageInfo类

3.实例

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