（1）编写index.jsp页面，用于收集投票信息
<%@ page language="java" pageEncoding="GBK"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>应用EL表达式显示投票结果</title>
<link rel="stylesheet" type="text/css" href="CSS/style.css">
</head>
<body><form name="form1" method="post" action="PollServlet">
<table width="403" height="230" border="0" align="center" cellpadding="0" cellspacing="1" bgcolor="#666666">
<tr>
<td height="30" bgcolor="#EFEFEF">·您最需要哪方面的编程类图书？</td>
</tr>
<tr>
<td bgcolor="#FFFFFF"> <input name="item" type="radio" class="noborder" value="基础教程类" checked>
基础教程类</td>
</tr>
<tr>
<td bgcolor="#FFFFFF"> <input name="item" type="radio" class="noborder" value="实例集锦类">
实例集锦类 </td>
</tr>
<tr>
<td bgcolor="#FFFFFF"> <input name="item" type="radio" class="noborder" value="经验技巧类">
经验技巧类</td>
</tr>
<tr>
<td bgcolor="#FFFFFF"> <input name="item" type="radio" class="noborder" value="速查手册类">
速查手册类</td>
</tr>
<tr>
<td bgcolor="#FFFFFF"> <input name="item" type="radio" class="noborder" value="案例剖析类">
案例剖析类</td>
</tr>
<tr>
<td align="center" bgcolor="#FFFFFF">
<input name="Submit" type="submit" class="btn_grey" value="投票">
<input name="Submit2" type="button" class="btn_grey" value="查看投票结果" onClick="window.location.href=‘showResult.jsp‘"></td>
</tr>
</table>
</form>
</body>
</html>
界面如下：
（2）编写投票功能的Servlet
package com.wuyudong.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.*;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class PollServlet extends HttpServlet {
private static final long serialVersionUID = -7264414153802032772L;
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to
* post.
*
* @param request
* the request send by the client to the server
* @param response
* the response send by the server to the client
* @throws ServletException
* if an error occurred
* @throws IOException
* if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("GBK"); // 设置请求的编码方式
String item = request.getParameter("item"); // 获取投票项
ServletContext servletContext = request.getSession()
.getServletContext(); // 获取ServletContext对象该对象在application范围内有效
Map map = null;
if (servletContext.getAttribute("pollResult") != null) {
map = (Map) servletContext.getAttribute("pollResult"); // 获取投票结果
map.put(item, Integer.parseInt(map.get(item).toString()) + 1); // 将当前的投票项加1
} else { // 初始化一个保存投票信息的Map集合，并将选定投票项的投票数设置为1，其他为0
String[] arr = { "基础教程类", "实例集锦类", "经验技巧类", "速查手册类", "案例剖析类" };
map = new HashMap();
for (int i = 0; i < arr.length; i++) {
if (item.equals(arr[i])) { // 判断是否为选定的投票项
map.put(arr[i], 1);
} else {
map.put(arr[i], 0);
}
}
}
servletContext.setAttribute("pollResult", map); // 保存投票结果到ServletContext对象中
response.setCharacterEncoding("GBK"); // 设置响应的编码方式，如果不设置弹出的对话框中的文字将乱码
PrintWriter out = response.getWriter();
out.println("<script>alert(‘投票成功！‘);window.location.href=‘showResult.jsp‘;</script>");
}
}
（3）编写showResult.jsp页面
<%@ page language="java" pageEncoding="GBK"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>显示示投票结果页面</title>
<link rel="stylesheet" type="text/css" href="CSS/style.css">
</head>
<body>
<table width="403" height="230" border="0" align="center" cellpadding="0" cellspacing="1" bgcolor="#666666">
<tr>
<td height="30" colspan="2" bgcolor="#EFEFEF">·您最需要哪方面的编程类图书？</td>
</tr>
<tr>
<td width="79" align="center" bgcolor="#FFFFFF"> 基础教程类</td>
<td width="321" bgcolor="#FFFFFF"> <img src="bar.gif" width=‘${220*(applicationScope.pollResult["基础教程类"]/(applicationScope.pollResult["基础教程类"]+applicationScope.pollResult["实例集锦类"]+applicationScope.pollResult["经验技巧类"]+applicationScope.pollResult["速查手册类"]+applicationScope.pollResult["案例剖析类"]))}‘ height="13">
（${empty applicationScope.pollResult["基础教程类"]? 0 :applicationScope.pollResult["基础教程类"]}）</td>
</tr>
<tr>
<td align="center" bgcolor="#FFFFFF"> 实例集锦类 </td>
<td bgcolor="#FFFFFF"> <img src="bar.gif" width=‘${220*(applicationScope.pollResult["实例集锦类"]/(applicationScope.pollResult["基础教程类"]+applicationScope.pollResult["实例集锦类"]+applicationScope.pollResult["经验技巧类"]+applicationScope.pollResult["速查手册类"]+applicationScope.pollResult["案例剖析类"]))}‘ height="13">
（${empty applicationScope.pollResult["实例集锦类"] ? 0 :applicationScope.pollResult["实例集锦类"]}）</td>
</tr>
<tr>
<td align="center" bgcolor="#FFFFFF"> 经验技巧类</td>
<td bgcolor="#FFFFFF"> <img src="bar.gif" width=‘${220*(applicationScope.pollResult["经验技巧类"]/(applicationScope.pollResult["基础教程类"]+applicationScope.pollResult["实例集锦类"]+applicationScope.pollResult["经验技巧类"]+applicationScope.pollResult["速查手册类"]+applicationScope.pollResult["案例剖析类"]))}‘ height="13">
（${empty applicationScope.pollResult["经验技巧类"] ? 0 :applicationScope.pollResult["经验技巧类"]}）</td>
</tr>
<tr>
<td align="center" bgcolor="#FFFFFF"> 速查手册类</td>
<td bgcolor="#FFFFFF"> <img src="bar.gif" width=‘${220*(applicationScope.pollResult["速查手册类"]/(applicationScope.pollResult["基础教程类"]+applicationScope.pollResult["实例集锦类"]+applicationScope.pollResult["经验技巧类"]+applicationScope.pollResult["速查手册类"]+applicationScope.pollResult["案例剖析类"]))}‘ height="13">
（${empty applicationScope.pollResult["速查手册类"] ? 0 : applicationScope.pollResult["速查手册类"]}）</td>
</tr>
<tr>
<td align="center" bgcolor="#FFFFFF"> 案例剖析类</td>
<td bgcolor="#FFFFFF"> <img src="bar.gif" width=‘${220*(applicationScope.pollResult["案例剖析类"]/(applicationScope.pollResult["基础教程类"]+applicationScope.pollResult["实例集锦类"]+applicationScope.pollResult["经验技巧类"]+applicationScope.pollResult["速查手册类"]+applicationScope.pollResult["案例剖析类"]))}‘ height="13">
（${empty applicationScope.pollResult["案例剖析类"] ? 0 :applicationScope.pollResult["案例剖析类"]}）</td>
</tr>
<tr>
<td colspan="2" align="center" bgcolor="#FFFFFF">
合计：${applicationScope.pollResult["基础教程类"]+applicationScope.pollResult["实例集锦类"]+applicationScope.pollResult["经验技巧类"]+applicationScope.pollResult["速查手册类"]+applicationScope.pollResult["案例剖析类"]}人投票！
<input name="Button" type="button" class="btn_grey" value="返回" onClick="window.location.href=‘index.jsp‘"></td>
</tr>
</table>
</body>
</html>
l>
最后运行界面如下：
时间： 2025-01-03 16:02:09