java--分页技术(2)

在http://blog.csdn.net/xanlv/article/details/53318076 java–分页技术(1)的基础上修改了一部分

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=${result.pageCount}<br/>
    showStart=${showStart},${showEnd}

    <h2>////////////展示分页的分页////////////</h2>
    <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="${showStart}" end="${showEnd}" 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/>
    <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>

    <h2>搜素</h2>
    <form action="<c:url value='/page'/>" method="post">

        ID中包含:<input type="text" name="id" value="${stud.id}"/>
        Name中包含:<input type="text" name="name" value="${stud.name}"/>
        <input type="submit"/>
    </form>





  </body>
</html>

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.domain.Stud;
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 {

        Stud stud=null;
        if(request.getMethod().equals("GET")){
//          System.out.println("det...");
            //先看看session中有没有旧的查询条件值对象stud
            stud=(Stud) request.getSession().getAttribute("stud");
            if(stud==null){
                stud=new Stud();
            }
        }else{
            //System.out.println("post....");
            //用Model封装查询条件---更好！
            String id=request.getParameter("id");
            String name=request.getParameter("name");
            stud=new Stud();
            stud.setId(id);
            stud.setName(name);
            request.getSession().setAttribute("stud", stud);
        }
        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,stud);
            //这里需要注意把service层和dao层对应的此方法的修改
//          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);
            //////////////相比上一版本增加下面这段代码//////////////////////
            //为实现分页的分页，只需在servlet中为前端补存:showStart和showEnd---显示的起始与终止页码
            //分页的分页
            int showSize=10;//每次显示几个页号
            int showStart=1;//显示的起始页号
//          int showEnd=showStart+showSize-1;
            int showEnd=0;//显示的终止页号
            int pageCount=Integer.valueOf(""+ result.get("pageCount"));
            //如果所有页码不足showSize则:  showStart=1, showEnd=pageCount
            if(showSize > pageCount){
                showEnd=pageCount;
                showStart=1;
            }else{
                System.out.println("iPageNo:"+iPageNo);
                //计算起始页号
                if(iPageNo<=(showSize/2)){
                    showStart=1;
                }else{
                    showStart=iPageNo-(showSize/2);
                }
                //计算终止页号
                showEnd=showStart+showSize-1;
                if(showEnd>pageCount){
                    showEnd=pageCount;
                    showStart=pageCount-showSize+1;
                }

            }
            request.setAttribute("showStart", showStart);
            request.setAttribute("showEnd", showEnd);

            //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!");
        }
    }

}

PageDaoJdbc.java

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.domain.Stud;
import cn.hncu.pubs.C3p0Utils;

public class PageDaoJdbc implements PageDAO {

    @Override
    public Map<String, Object> query(Integer iPageNo,Stud stud) throws Exception {
        int pageSize=10;//每页显示20行，本例这里写死了
        Map<String, Object> result=new HashMap<String,Object>();
        //构造条件查询的sql,包含两条，一条用于查询总行数，另一条查数据行
//      String sql_1="select count(1) from student where 1=1";
        String sql_1="select count(1) from student where 1=1";//查询总行数
        String sql_2="select * from student where 1=1";//查询当前页要显示的内容(数据行)
        if(stud.getId()!=null&& !stud.getId().trim().equals("")){
            sql_1+=" and id like '%"+stud.getId()+"%'";
            sql_2+=" and id like '%"+stud.getId()+"%'";
        }
        if(stud.getName()!=null&& !stud.getName().trim().equals("")){
            sql_1+=" and name like '%"+stud.getName()+"%'";
            sql_2+=" and name like '%"+stud.getName()+"%'";
        }
        System.out.println("sql_1:"+sql_1);
        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);
        int startN = (iPageNo-1)*pageSize;//从哪一行开始显示
//      if(startN==0){
//          startN=1;
//      }
        sql_2+=" limit "+startN+","+pageSize;
//      System.out.println("sql_2:"+sql_2);
        //查询当前页要显示的内容(数据行)
//      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;
    }

}