Mybatis 分页插件 PageHelper

　　话不多说，直接导入、部署流程。

1. 引入插件依赖包：

　　maven工程中，pom.xml文件下，添加插件配置项:

　　

2. 配置插件拦截器：

　　webapp -> WEB-INF 下添加 .xml配置文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true" />
    </settings>
    <plugins>
        <!-- com.github.pagehelper为PageHelper类所在包名 -->
        <plugin interceptor="com.github.pagehelper.PageHelper">
　　　　　　　<!-- 方言 -->
            <property name="dialect" value="sqlserver"/>
            <!-- 该参数默认为false -->
            <!-- 设置为true时，会将RowBounds第一个参数offset当成pageNum页码使用 -->
            <!-- 和startPage中的pageNum效果一样-->
            <property name="offsetAsPageNum" value="true"/>
            <!-- 该参数默认为false -->
            <!-- 设置为true时，使用RowBounds分页会进行count查询 -->
            <property name="rowBoundsWithCount" value="true"/>
            <!-- 设置为true时，如果pageSize=0或者RowBounds.limit = 0就会查询出全部的结果 -->
            <!-- （相当于没有执行分页查询，但是返回结果仍然是Page类型）-->
            <property name="pageSizeZero" value="true"/>
            <!-- 3.3.0版本可用 - 分页参数合理化，默认false禁用 -->
            <!-- 启用合理化时，如果pageNum<1会查询第一页，如果pageNum>pages会查询最后一页 -->
            <!-- 禁用合理化时，如果pageNum<1或pageNum>pages会返回空数据 -->
            <property name="reasonable" value="false"/>
            <!-- 3.5.0版本可用 - 为了支持startPage(Object params)方法 -->
            <!-- 增加了一个`params`参数来配置参数映射，用于从Map或ServletRequest中取值 -->
            <!-- 可以配置pageNum,pageSize,count,pageSizeZero,reasonable,不配置映射的用默认值 -->
            <!-- 不理解该含义的前提下，不要随便复制该配置 -->
            <property name="params" value="pageNum=start;pageSize=limit;"/>
            <!-- always总是返回PageInfo类型,check检查返回类型是否为PageInfo,none返回Page -->
            <property name="returnPageInfo" value="check"/>
        </plugin>
    </plugins>
</configuration>

3.使用方式:　　

　　

4.源码:

　　

import com.github.pagehelper.Page;

import java.io.Serializable;
import java.util.Collection;
import java.util.List;

/**
 * 2018/6/8
 * @author pp
 */
public class PageInfoUtils<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;
    /** 排序 */
    private String orderBy;
    /** 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;
    /** 第一页 */
    private int firstPage;
    /** 前一页 */
    private int prePage;
    /** 下一页 */
    private int nextPage;
    /** 最后一页 */
    private int lastPage;
    /** 是否为第一页 */
    private boolean isFirstPage;
    /** 是否为最后一页 */
    private boolean isLastPage;
    /** 是否有前一页 */
    private boolean hasPreviousPage;
    /** 是否有下一页 */
    private boolean hasNextPage;
    /** 导航页码数 */
    private int navigatePages;
    /** 所有导航页号 */
    private int[] navigatepageNums;


    public PageInfoUtils() {
        this.isFirstPage = false;
        this.isLastPage = false;
        this.hasPreviousPage = false;
        this.hasNextPage = false;
    }
    /**
     * 包装Page对象
     *
     * @param list
     */
    public PageInfoUtils(List<T> list) {
        this(list, 8);
    }
    /**
     * 包装Page对象
     *
     * @param list          page结果
     * @param navigatePages 页码数量
     */
    public PageInfoUtils(List<T> list, int navigatePages) {
        this.isFirstPage = false;
        this.isLastPage = false;
        this.hasPreviousPage = false;
        this.hasNextPage = false;
        if (list instanceof Page) {
            Page page = (Page)list;
            this.pageNum = page.getPageNum();
            this.pageSize = page.getPageSize();
            this.orderBy = page.getOrderBy();
            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+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 = 1;
            this.list = list;
            this.size = list.size();
            this.total = (long)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
            this.calcNavigatepageNums();
            //计算前后页，第一页，最后一页
            this.calcPage();
            //判断页面边界
            this.judgePageBoudary();
        }

    }

    public PageInfoUtils(List<T> list, int pageNum, int pageSize,int navigatePages) {
        if (0 == navigatePages) {
            navigatePages = 8;
        }
        this.isFirstPage = false;
        this.isLastPage = false;
        this.hasPreviousPage = false;
        this.hasNextPage = false;
        if (list instanceof Page) {
            Page page = (Page)list;
            this.pageNum = page.getPageNum();
            this.pageSize = page.getPageSize();
            this.orderBy = page.getOrderBy();
            this.pages = page.getPages();
            this.list = page;
            this.size = page.size();
            this.total = page.getTotal();
            if (this.size == 0) {
                this.startRow = 0;
                this.endRow = 0;
            } else {
                this.startRow = page.getStartRow() + 1;
                this.endRow = this.startRow - 1 + this.size;
            }
        } else if (list instanceof Collection) {
            this.pageNum = pageNum;
            this.pageSize = pageSize;
            if (list.size() > 0) {
                int listSize = list.size();
                this.pages = (listSize / pageSize) + 1;
                this.list = list.subList(pageNum * pageSize, (pageNum + 1) * pageSize);
            } else {
                this.pages = list.size();
                this.list = list;
            }

            this.size = pageSize;
            this.total = (long) list.size();
            this.startRow = list.size() > 0 ? (pageNum - 1) * pageSize + 1 : 0;
            this.endRow = list.size() > 0 ? pageNum * pageSize : 0;
        }

        if (list instanceof Collection) {
            this.navigatePages = navigatePages;
            this.calcNavigatepageNums();
            this.calcPage();
            this.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 (this.pages <= this.navigatePages) {
            this.navigatepageNums = new int[this.pages];
            for(int i = 0; i < this.pages; ++i) {
                this.navigatepageNums[i] = i + 1;
            }
        } else {//当总页数大于导航页码数时
            this.navigatepageNums = new int[this.navigatePages];
            int startNum = this.pageNum - this.navigatePages / 2;
            int endNum = this.pageNum + this.navigatePages / 2;
            if (startNum < 1) {
                startNum = 1;
                //(最前navigatePages页
                for(int i = 0; i < this.navigatePages; ++i) {
                    this.navigatepageNums[i] = startNum++;
                }
            } else if (endNum > this.pages) {
                endNum = this.pages;
                //最后navigatePages页
                for(int i = this.navigatePages - 1; i >= 0; --i) {
                    this.navigatepageNums[i] = endNum--;
                }
            } else {
                //所有中间页
                for(int i = 0; i < this.navigatePages; ++i) {
                    this.navigatepageNums[i] = startNum++;
                }
            }
        }

    }
    /**
     * 计算前后页，第一页，最后一页
     */
    private void calcPage() {
        if (this.navigatepageNums != null && this.navigatepageNums.length > 0) {
            this.firstPage = this.navigatepageNums[0];
            this.lastPage = this.navigatepageNums[this.navigatepageNums.length - 1];
            if (this.pageNum > 1) {
                this.prePage = this.pageNum - 1;
            }

            if (this.pageNum < this.pages) {
                this.nextPage = this.pageNum + 1;
            }
        }

    }
    /**
     * 判定页面边界
     */
    private void judgePageBoudary() {
        this.isFirstPage = this.pageNum == 1;
        this.isLastPage = this.pageNum == this.pages;
        this.hasPreviousPage = this.pageNum > 1;
        this.hasNextPage = this.pageNum < this.pages;
    }

    public int getPageNum() {
        return this.pageNum;
    }

    public void setPageNum(int pageNum) {
        this.pageNum = pageNum;
    }

    public int getPageSize() {
        return this.pageSize;
    }

    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }

    public int getSize() {
        return this.size;
    }

    public void setSize(int size) {
        this.size = size;
    }

    public String getOrderBy() {
        return this.orderBy;
    }

    public void setOrderBy(String orderBy) {
        this.orderBy = orderBy;
    }

    public int getStartRow() {
        return this.startRow;
    }

    public void setStartRow(int startRow) {
        this.startRow = startRow;
    }

    public int getEndRow() {
        return this.endRow;
    }

    public void setEndRow(int endRow) {
        this.endRow = endRow;
    }

    public long getTotal() {
        return this.total;
    }

    public void setTotal(long total) {
        this.total = total;
    }

    public int getPages() {
        return this.pages;
    }

    public void setPages(int pages) {
        this.pages = pages;
    }

    public List<T> getList() {
        return this.list;
    }

    public void setList(List<T> list) {
        this.list = list;
    }

    public int getFirstPage() {
        return this.firstPage;
    }

    public void setFirstPage(int firstPage) {
        this.firstPage = firstPage;
    }

    public int getPrePage() {
        return this.prePage;
    }

    public void setPrePage(int prePage) {
        this.prePage = prePage;
    }

    public int getNextPage() {
        return this.nextPage;
    }

    public void setNextPage(int nextPage) {
        this.nextPage = nextPage;
    }

    public int getLastPage() {
        return this.lastPage;
    }

    public void setLastPage(int lastPage) {
        this.lastPage = lastPage;
    }

    public boolean isIsFirstPage() {
        return this.isFirstPage;
    }

    public void setIsFirstPage(boolean isFirstPage) {
        this.isFirstPage = isFirstPage;
    }

    public boolean isIsLastPage() {
        return this.isLastPage;
    }

    public void setIsLastPage(boolean isLastPage) {
        this.isLastPage = isLastPage;
    }

    public boolean isHasPreviousPage() {
        return this.hasPreviousPage;
    }

    public void setHasPreviousPage(boolean hasPreviousPage) {
        this.hasPreviousPage = hasPreviousPage;
    }

    public boolean isHasNextPage() {
        return this.hasNextPage;
    }

    public void setHasNextPage(boolean hasNextPage) {
        this.hasNextPage = hasNextPage;
    }

    public int getNavigatePages() {
        return this.navigatePages;
    }

    public void setNavigatePages(int navigatePages) {
        this.navigatePages = navigatePages;
    }

    public int[] getNavigatepageNums() {
        return this.navigatepageNums;
    }

    public void setNavigatepageNums(int[] navigatepageNums) {
        this.navigatepageNums = navigatepageNums;
    }

    public String toString() {
        StringBuffer sb = new StringBuffer("PageInfoUtils{");
        sb.append("pageNum=").append(this.pageNum);
        sb.append(", pageSize=").append(this.pageSize);
        sb.append(", size=").append(this.size);
        sb.append(", startRow=").append(this.startRow);
        sb.append(", endRow=").append(this.endRow);
        sb.append(", total=").append(this.total);
        sb.append(", pages=").append(this.pages);
        sb.append(", list=").append(this.list);
        sb.append(", firstPage=").append(this.firstPage);
        sb.append(", prePage=").append(this.prePage);
        sb.append(", nextPage=").append(this.nextPage);
        sb.append(", lastPage=").append(this.lastPage);
        sb.append(", isFirstPage=").append(this.isFirstPage);
        sb.append(", isLastPage=").append(this.isLastPage);
        sb.append(", hasPreviousPage=").append(this.hasPreviousPage);
        sb.append(", hasNextPage=").append(this.hasNextPage);
        sb.append(", navigatePages=").append(this.navigatePages);
        sb.append(", navigatepageNums=");
        if (this.navigatepageNums == null) {
            sb.append("null");
        } else {
            sb.append('[');

            for(int i = 0; i < this.navigatepageNums.length; ++i) {
                sb.append(i == 0 ? "" : ", ").append(this.navigatepageNums[i]);
            }

            sb.append(']');
        }

        sb.append('}');
        return sb.toString();
    }
}