实习备忘录之分页技术

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web网页之分页技术

1.添加插件

首先，要在pom文件里面添加依赖：

<!--   分页jar包      -->
<dependency>
  <groupId>com.github.pagehelper</groupId>
  <artifactId>pagehelper</artifactId>
  <version>5.1.2</version>
</dependency>

然后在applicationContext.xml里面找到，表示配置SqlSessionFactory对象的bean标签：

加入如下代码：

<!--此处导入分页功能的插件-->
<property name="plugins">
    <array>
        <bean class="com.github.pagehelper.PageInterceptor">
            <property name="properties">
                <props>
                    <prop key="helperDialect"></prop>
                    <prop key="reasonable">true</prop>
                </props>
            </property>
        </bean>
    </array>
</property>

2.mybatis分页工具PageHelper中PageInfo相关属性

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.youkuaiyun.com/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+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.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;
    }

    @Deprecated
    public 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;
    }

    @Deprecated
    public 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;
    }

    @Override
    public 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();
    }
}