java--分页技术(1)

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项目代码结构

<%@ 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>学生信息</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}页</option>             --%>            <option <c:if test="${idx==result.currentPage}">selected</c:if> value="${idx}">第${idx}页</option>        </c:forEach>    </select>    <br/><br/>    <c:if test="${result.currentPage>1}">        <a href='<c:url value="/page?pageNo=${result.currentPage-1}"></c:url>'>上一页</a>&nbsp;    </c:if>    <c:forEach begin="1" end="${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>'>下一页</a>&nbsp;    </c:if>    <br/><br/>   &nbsp;   &nbsp;     </body></html>

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

值对象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层
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 {    //依赖注入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";//默认查询第1页        }        try {            //把页码转成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"));            //再补一个结果3: 当前页码            result.put("currentPage", iPageNo);            //结果数据一定要放在容器中            request.setAttribute("result", result);            //转发到结果页面去显示            request.getRequestDispatcher("/jsps/show.jsp").forward(request, response);        } catch (NumberFormatException e) {            response.getWriter().println("页码格式错误!");        } catch (Exception e) {            response.getWriter().println("数据库查询错误!");        }    }}

service层

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

dao层

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;//每页显示10行，本例这里写死了        Map<String, Object> result=new HashMap<String,Object>();        //查询总行数        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封装返回结果是1行1列的数据//      System.out.println("pageCount:"+obj.toString());        int rows=Integer.parseInt(obj.toString());        //计算出总页数//      int pageCount=rows/iPageNo+rows%iPageNo==0?0:1;        int pageCount=rows/pageSize+(rows%pageSize==0?0:1);        result.put("pageCount", pageCount);//结果1        System.out.println("row:"+rows);        System.out.println("pageCount:"+pageCount);        //查询当前页要显示的内容(数据行)        int startN = (iPageNo-1)*pageSize;//从哪一行开始显示        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);//结果2//      System.out.println("ll"+result.get("students"));        return result;    }}

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