java--分頁技術(1)

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<html>

  <body>
    <c:redirect url="/page"></c:redirect>
  </body>
</html>

show.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<html>
  <head>
    <script type="text/javascript">
        function sub(obj){
            window.location.href="<c:url value='/page?pageNo="+obj.value+"'/>";
        }
    </script>
  </head>

  <body>
    <h3>學生信息</h3>
    <c:forEach items="${result.students}" var="s">
        id=${s.id},,,name=${s.name}<br/>
    </c:forEach>

    pageCount=${result.pageCount}<br/>
    &nbsp;   &nbsp;   &nbsp;   &nbsp;
    <select onchange="sub(this)">
        <c:forEach begin="1" end="${result.pageCount}" var="idx">
            <%--
                <option selected='<c:if test="${idx==result.currentPage}">selected</c:if>' value="${idx}">第${idx}頁</option>
             --%>
            <option <c:if test="${idx==result.currentPage}">selected</c:if> value="${idx}">第${idx}頁</option>
        </c:forEach>
    </select>
    <br/><br/>
    <c:if test="${result.currentPage>1}">
        <a href='<c:url value="/page?pageNo=${result.currentPage-1}"></c:url>'>上一頁</a>&nbsp;
    </c:if>
    <c:forEach begin="1" end="${result.pageCount}" var="idx">
        <c:if test="${result.currentPage==idx}">
            ${idx}
        </c:if>
        <c:if test="${result.currentPage!=idx}">
            <a href='<c:url value="/page?pageNo=${idx}"></c:url>'>${idx}</a>&nbsp;
        </c:if>
    </c:forEach>
    <c:if test="${result.currentPage<result.pageCount}">
        <a href='<c:url value="/page?pageNo=${result.currentPage+1}"></c:url>'>下一頁</a>&nbsp;
    </c:if>
    <br/><br/>   &nbsp;   &nbsp;   

  </body>
</html>

C3p0Utils.java見http://blog.csdn.net/xanlv/article/details/53266493

值對象Stud.java

package cn.hncu.domain;

public class Stud {

    private String id;
    private String name;

    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "stud =" + id + "," + name;
    }

}

servlet層
PageServlet.java

package cn.hncu.servlet;
import java.io.IOException;
import java.util.Map;

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

import cn.hncu.service.IPageService;
import cn.hncu.service.PageServiceImpl;


public class PageServlet extends HttpServlet {

    //依賴注入service
    IPageService service=new PageServiceImpl();
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doPost(request, response);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        String pageNo=request.getParameter("pageNo");
        if(pageNo==null||pageNo.equals("")){
            pageNo="1";//默認查詢第1頁
        }

        try {
            //把頁碼轉成int
            int iPageNo=Integer.parseInt(pageNo);
            Map<String, Object> result=service.query(iPageNo);
//          System.out.println("--"+result.get("pageCount"));
//          System.out.println("--"+result.get("students"));
            //再補一個結果3: 當前頁碼
            result.put("currentPage", iPageNo);
            //結果數據一定要放在容器中
            request.setAttribute("result", result);
            //轉發到結果頁面去顯示
            request.getRequestDispatcher("/jsps/show.jsp").forward(request, response);
        } catch (NumberFormatException e) {
            response.getWriter().println("頁碼格式錯誤!");
        } catch (Exception e) {
            response.getWriter().println("數據庫查詢錯誤!");
        }
    }

}

service層

package cn.hncu.service;

import java.util.Map;

public interface IPageService {

    public Map<String, Object> query(Integer iPageNo) throws Exception ;
}

package cn.hncu.service;

import java.util.Map;

import cn.hncu.dao.PageDAO;
import cn.hncu.dao.PageDaoJdbc;

public class PageServiceImpl implements IPageService {

    //依賴注入dao
    PageDAO dao=new PageDaoJdbc();
    @Override
    public Map<String, Object> query(Integer iPageNo) throws Exception {
        return dao.query(iPageNo);
    }

}

dao層

package cn.hncu.dao;

import java.util.Map;

public interface PageDAO {

    public Map<String, Object> query(Integer iPageNo) throws Exception ;
}

package cn.hncu.dao;

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

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

import cn.hncu.pubs.C3p0Utils;

public class PageDaoJdbc implements PageDAO {

    @Override
    public Map<String, Object> query(Integer iPageNo) throws Exception {
        int pageSize=20;//每頁顯示10行，本例這裏寫死了
        Map<String, Object> result=new HashMap<String,Object>();
        //查詢總行數
        String sql_1="select count(1) from student";
        QueryRunner run=new QueryRunner(C3p0Utils.getDataSource());
        Object obj=run.query(sql_1, new ScalarHandler());//使用ScalarHandler封裝返回結果是1行1列的數據
//      System.out.println("pageCount:"+obj.toString());
        int rows=Integer.parseInt(obj.toString());
        //計算出總頁數
//      int pageCount=rows/iPageNo+rows%iPageNo==0?0:1;
        int pageCount=rows/pageSize+(rows%pageSize==0?0:1);
        result.put("pageCount", pageCount);//結果1
        System.out.println("row:"+rows);
        System.out.println("pageCount:"+pageCount);
        //查詢當前頁要顯示的內容(數據行)
        int startN = (iPageNo-1)*pageSize;//從哪一行開始顯示
        String sql_2="select * from student limit "+startN+","+pageSize;
//      List<Map<String, String>> students=run.query(sql_2, new MapListHandler());//error
        List<Map<String, Object>> students=run.query(sql_2, new MapListHandler());
//      System.out.println(students);
        result.put("students", students);//結果2
//      System.out.println("ll"+result.get("students"));
        return result;
    }

}