分頁查詢 原理以及網頁實現固定頁碼數 搜索的實現

需求：做出類似百度這樣頁碼限制的數據分頁查詢的功能網頁

在數據庫中通過數據的總行數以及你想要每次獲取多少數據，就可以得到想要的頁數

總頁數 = 總行數/pageSize + (行數%pageSize==0?0:1);

所以獲取數據的方法：

package cn.hncu.dao;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.faces.model.ScalarDataModel;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.MapListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

import cn.hncu.domain.Stud;
import cn.hncu.pubs.dbutilsC3po;

public class PageDaoImpl implements PageDAO {

    @Override
    public Map<String, Object> query(Integer pageNo, Stud s) throws Exception {
        Map<String, Object> result = new HashMap<String, Object>();
        int pageSize = 10;// 假定每頁顯示十行

        // 計算總頁數
        // 總頁數 = 總行數/pageSize + (行數%pageSize==0?0:1);

        // 查詢總行數
        int startN = (pageNo - 1) * pageSize;
        String sql = "select count(1) from stud2 where 1=1";
        String sql2 = "select * from stud2 where 1=1 ";
        if (s.getId() != null && s.getId().trim().length() > 0) {
            sql = sql + " and id like '%" + s.getId().trim() + "%'";
            sql2 = sql2 + " and id like '%" + s.getId().trim() + "%'";
        }
        if (s.getName() != null && s.getName().trim().length() > 0) {
            sql = sql + " and name like '%" + s.getName().trim() + "%'";
            sql2 = sql2 + " and name like '%" + s.getName().trim() + "%'";
        }

        QueryRunner run = new QueryRunner(dbutilsC3po.getDataSource());
        int rows = Integer.parseInt("" + run.query(sql, new ScalarHandler()));
        // 總頁數
        int pageCount = rows / pageSize + (rows % pageSize == 0 ? 0 : 1);
        result.put("pagecount", pageCount);
        result.put("pagesize", pageSize);

        sql2 = sql2 + " limit " + startN + "," + pageSize;
        List<Map<String, Object>> studs = run.query(sql2, new MapListHandler());

        result.put("studs", studs);
        return result;
    }

}

那麼我們應該如何將這些數據在頁面中顯示並且限制它的頁數呢

package cn.hncu.pubs;

import java.util.Map;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class pageUtils {

    /**
     * 計算顯示當前分頁的起始頁
     * 
     * @param pageNum
     *            當前頁碼
     * @param pageCount
     *            總頁數
     * @param sideNum
     *            分頁係數 分頁條中顯示幾個數字頁碼。 顯示數字頁碼個數 = 2 * sideNum + 1
     * @param result
     * @param response
     * @param request
     */
    public static void calcPage(int pageNum, int pageCount, int sideNum,
            Map<String, Object> result) {
        int startNum = 0;//要計算出頁面第一個頁數
        int endNum = 0;//要計算出頁面最後一個頁數

        if (pageCount <= sideNum) {
            endNum = pageCount;
        } else {
            if ((sideNum + pageNum) >= pageCount) {
                endNum = pageCount;
            } else {
                endNum = sideNum + pageNum;
                if ((sideNum + pageNum) <= (2 * sideNum + 1)) {
                    if ((2 * sideNum + 1) >= pageCount) {
                        endNum = pageCount;
                    } else {
                        endNum = 2 * sideNum + 1;
                    }
                } else {
                    endNum = sideNum + pageNum;
                }
            }
        }

        if (pageNum <= sideNum) {
            startNum = 1;
        } else {
            if ((pageNum + sideNum) >= pageCount) {
                if ((2 * sideNum + 1) >= pageCount) {
                    if ((pageCount - 2 * sideNum) >= 1) {
                        startNum = pageCount - 2 * sideNum;
                    } else {
                        startNum = 1;
                    }
                } else {
                    startNum = pageCount - 2 * sideNum;
                }
            } else {
                if ((pageNum - sideNum) >= 1) {
                    startNum = pageNum - sideNum;
                } else {
                    startNum = 1;
                }
            }
        }
        result.put("startNum", startNum);
        result.put("endNum", endNum);
    }

}

然後通過jstl+el在頁面獲取數據：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>

<title>分頁查詢結果頁面</title>


</head>

<body>
    <c:forEach items="${results.studs }" var="s">
        ${s.id}&nbsp;${s.name}<br />
    </c:forEach>
</body>
<hr />
<c:if test="${results.currentPage!=1}">
    <a
        href="<c:url value='/PageServlet?pageno=${results.currentPage-1}' />">
        上一頁 </a>&nbsp;&nbsp;
    </c:if>
<c:forEach begin="${results.startNum }" end="${results.endNum }"
    var="idx">
    <c:if test="${results.currentPage==idx}">
         ${idx} &nbsp;
      </c:if>

    <c:if test="${results.currentPage!=idx}">
        <a href="<c:url value='/PageServlet?pageno=${idx}' />"> ${idx} </a>&nbsp;&nbsp;
      </c:if>
</c:forEach>
<c:if test="${results.currentPage!=results.pagecount}">
    <a
        href="<c:url value='/PageServlet?pageno=${results.currentPage+1}' />">
        下一頁 </a>&nbsp;&nbsp;
    </c:if>
&nbsp;&nbsp;
<select onchange="sub(this);">
    <c:forEach begin="1" end="${results.pagecount}" var="idx">
        <option <c:if test='${idx==results.currentPage}'>selected</c:if>
            value="${idx}">第${idx}頁</option>
    </c:forEach>
</select>
<form action="<c:url value='/PageServlet'/>" method="post">
    id中包含:<input type="text" name="id" /> <br/>
    name中包含:<input type="text" name="name" /> <br/>
    <input type="submit" name="addquery" value="查詢" />
</form>
<script type="text/javascript">
    function sub(obj) {
        window.location.href = "<c:url value='/PageServlet?pageno='/>"
                + obj.value;
    }
</script>
</html>