Java project: voting system
Today, I bring you a small voting system written in java. The code is simple and suitable for beginners to practice!
Code display:
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");    //Set the encoding of the request
    String item=request.getParameter("item");   //Get votes
    ServletContext servletContext=request.getSession().getServletContext(); //Get the ServletContext object, which is valid in the application scope
    Map map=null;
    if(servletContext.getAttribute("pollResult")!=null){
        map=(Map)servletContext.getAttribute("pollResult"); //Get voting results
        map.put(item,Integer.parseInt(map.get(item).toString())+1); //Add 1 to the current vote
    }else{      //Initialize a Map collection to save voting information, and set the number of votes for the selected voting items to 1, and the others to 0
        String[] arr={"Basic tutorial class","Instance collection class","Experience and skill","Quick reference manual","Case analysis"};
        map=new HashMap();
        for(int i=0;i<arr.length;i++){
            if(item.equals(arr[i])){    //Determine if it is a selected vote
                map.put(arr[i], 1);
            }else{
                map.put(arr[i], 0);
            }
        }
    }
    servletContext.setAttribute("pollResult", map); //Save voting results to ServletContext object
    response.setCharacterEncoding("GBK");       //Set the encoding method of the response. If you do not set the text in the pop-up dialog box, it will be garbled
    PrintWriter out=response.getWriter();
    out.println("<script>alert('Vote successfully!');window.location.href='showResult.jsp';</script>");

}

}
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