Java制作投票系统代码

package com.tarena.wgh.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 {/** * 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>");

}}