分页技术-总结

在进行分页的时候，必须知道三个信息：当前页，每页显示记录数，以及总记录数。

所以除了一个Page类，还需一个createPage类，后者构造方法需要三个参数：当前页，每页显示记录数，以及总记录数。

之后后台封装好page类，传递给前端，显示。

一个项目中的Page类：

package com.sanqing.util;
public class Page {
    private int everyPage;            //每页显示记录数
    private int totalCount;            //总记录数
    private int totalPage;            //总页数
    private int currentPage;        //当前页
    private int beginIndex;            //查询起始点
    private boolean hasPrePage;        //是否有上一页
    private boolean hasNextPage;    //是否有下一页
    public Page(int everyPage, int totalCount, int totalPage, 
            int currentPage,int beginIndex, boolean hasPrePage,
            boolean hasNextPage) {    //自定义构造方法
        this.everyPage = everyPage;
        this.totalCount = totalCount;
        this.totalPage = totalPage;
        this.currentPage = currentPage;
        this.beginIndex = beginIndex;
        this.hasPrePage = hasPrePage;
        this.hasNextPage = hasNextPage;
    }
    public Page(){}                    //默认构造函数
    public int getEveryPage() {        //获得每页显示记录数
        return everyPage;
    }
    public void setEveryPage(int everyPage) {//设置每页显示记录数
        this.everyPage = everyPage;
    }
    public int getTotalCount() {//获得总记录数
        return totalCount;
    }
    public void setTotalCount(int totalCount) {//设置总记录数
        this.totalCount = totalCount;
    }
    public int getTotalPage() {//获得总页数
        return totalPage;
    }
    public void setTotalPage(int totalPage) {//设置总页数
        this.totalPage = totalPage;
    }
    public int getCurrentPage() {//获得当前页
        return currentPage;
    }
    public void setCurrentPage(int currentPage) {//设置当前页
        this.currentPage = currentPage;
    }
    public int getBeginIndex() {//获得查询起始点
        return beginIndex;
    }
    public void setBeginIndex(int beginIndex) {//设置查询起始点
        this.beginIndex = beginIndex;
    }
    public boolean isHasPrePage() {//获得是否有上一页
        return hasPrePage;
    }
    public void setHasPrePage(boolean hasPrePage) {//设置是否有上一页
        this.hasPrePage = hasPrePage;
    }
    public boolean isHasNextPage() {//获得是否有下一页
        return hasNextPage;
    }
    public void setHasNextPage(boolean hasNextPage) {//设置是否有下一页
        this.hasNextPage = hasNextPage;
    }
}

Page辅助类，其构造函数只需要当前页，每页显示记录数，以及总记录数，便可计算出其它：

package com.sanqing.util;
/*
 * 分页信息辅助类
 */
public class PageUtil {
    public static Page createPage(int everyPage,int totalCount,int currentPage) {//创建分页信息对象
        everyPage = getEveryPage(everyPage);
        currentPage = getCurrentPage(currentPage);
        int totalPage = getTotalPage(everyPage, totalCount);
        int beginIndex = getBeginIndex(everyPage, currentPage);
        boolean hasPrePage = getHasPrePage(currentPage);
        boolean hasNextPage = getHasNextPage(totalPage, currentPage);
        return new Page(everyPage, totalCount, totalPage, currentPage,
                beginIndex, hasPrePage,  hasNextPage);
    }
    public static int getEveryPage(int everyPage) {        //获得每页显示记录数
        return everyPage == 0 ? 10 : everyPage;
    }
    public static int getCurrentPage(int currentPage) {    //获得当前页
        return currentPage == 0 ? 1 : currentPage;
    }
    public static int getTotalPage(int everyPage,int totalCount) {//获得总页数
        int totalPage = 0;
        if(totalCount != 0 &&totalCount % everyPage == 0) {
            totalPage = totalCount / everyPage;
        } else {
            totalPage = totalCount / everyPage + 1;
        }
        return totalPage;
    }
    public static int getBeginIndex(int everyPage,int currentPage) {//获得起始位置
        return (currentPage - 1) * everyPage;
    }
    public static boolean getHasPrePage(int currentPage) {//获得是否有上一页
        return currentPage == 1 ? false : true;
    }
    public static boolean getHasNextPage(int totalPage, int currentPage) {    //获得是否有上一页
        return currentPage == totalPage || totalPage == 0 ? false : true;
    }
}

实践中的一次应用：servlet代码

        //获得该消息对应的所有回复
        int currentPage = 0;
        String currentPageStr = request.
                    getParameter("currentPage");//获得消息回复列表的当前页信息
        if(currentPageStr == null || "".equals(currentPageStr)){
            currentPage = 1;
        }else {
            currentPage = Integer.parseInt(currentPageStr);
        }
        ReplyDAO replayDAO = ReplyDAOFactory.getReplyDAOInstance();
        Page page = PageUtil.createPage(5, replayDAO.
                        findCountByMsgID(messageID), currentPage);//设置分页信息
        List<Reply> replys = replayDAO.
                        findReplayByMsgID(messageID, page);//分页查询消息回复
        request.setAttribute("replyList", replys);//保存消息回复列表
        request.setAttribute("page", page);//保存分页信息
        
        //获得该消息对象的批复
        CriticismDAO criticismDAO = CriticismDAOFactory.getCriticismDAOInstance();
        Criticism criticism = criticismDAO.findCriticismByMsgID(messageID);
        request.setAttribute("criticism", criticism);
        
        ServletContext servletContext = getServletContext();
        RequestDispatcher dispatcher = servletContext.
                    getRequestDispatcher("/showMsg.jsp");    //跳转到消息显示页
        dispatcher.forward(request, response);

前端页面是根据后台传递的page对象处理分页信息。两种方式：