本文实例为大家分享了javaweb实现投票系统的具体代码，供大家参考，具体内容如下
这次给大家带来一个课堂基础作业，简单的javaweb投票系统。
当然也设计了添加投票人的接口，只是list页面没有直接导航过去。
如页面显示，可以增加和减少相应的票数。同时id是利用数据库该字段作为主键自增的。 name 和头像都是上传的，由mysql数据库存储照片名然后再自动寻找到。票数是直接由user_votes存储使用。
接下来带来关键代码。
//这是类User_list
package com.example.user_votes;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Driver;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
@WebServlet("/list")
public class User_list extends HelloServlet{
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//连接数据库，获取所有的用户信息
//创建一个用户对象
List<User> userlist = new ArrayList<User>();
try {
// 1.加载驱动程序
// DriverManager.registerDriver(new com.mysql.cj.jdbc.Driver());
Class.forName("com.mysql.cj.jdbc.Driver");
// 2.创建数据库连接
String url = "jdbc:mysql://localhost:3306/java_test?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC";
String jdbcuser = "root";
String jdbcpwd = "500400";
Connection conn = DriverManager.getConnection(url, jdbcuser, jdbcpwd);
// 3.创建语句对象
Statement stmt = conn.createStatement();
// 4.执行sql
// 被注释的代码是插入数据
String sql ="SELECT * from user_votes";
//动态操作
ResultSet rows = stmt.executeQuery(sql);
// 5.处理结果 rows.next() 用于遍历rows对象集
while(rows.next()){
User user = new User();
user.setId(rows.getInt("id"));
user.setName(rows.getString("user_name"));
user.setUrl(rows.getString("url"));
user.setVotes(Integer.parseInt(rows.getString("votes")));
userlist.add(user);
}
// 6.关闭语句对象，数据库连接rows.close()关闭row对象集
rows.close();
stmt.clearBatch();
conn.close();
} catch (Exception e) {
System.out.println("获取用户列表失败" e.getMessage());
e.printStackTrace();
}
//返回响应，以表格的方式显示所有用户
resp.setContentType("text/html");
resp.setCharacterEncoding("utf-8");
PrintWriter out =resp.getWriter();
out.println("<html><head><title>投票系统</title></head><body>");
if (userlist.size()>0){
out.println("<table>");
out.println("<caption></caption>");
out.println("<tr>");
out.println("<th>id</th>");
out.println("<th style=\"\n"
" padding-left: 10px; text-align: left;\n"
"\">Name</th>");
out.println("<th>照片</th>");
out.println("<th>votes</th>");
out.println("<th>操作</th>");
out.println("</tr>");
for (User user:userlist){
out.println("<tr>");
out.println("<td>" user.getId() "</td>");
out.println("<td>" "   " user.getName() "</td>");
out.println("<td><img width = '30px' height = '30px' src=" "/photo/" user.getUrl() ".jpg" "></td>");
out.println("<td>" "   " user.getVotes() "</td>");
out.println("<td><a href=add?id=" user.getId() "&votes=" user.getVotes() ">add</a> <a href=delete?id=" user.getId() "&votes=" user.getVotes() ">删除</a></td>");
out.println("</tr>");
}
out.println("</table>");
out.println("");
}else{
out.println("暂无用户");
}
out.println();
out.println("</body></html>
}
}这一段是用于list页面的展示代码。
同时以下是增减票数的代码。
//这个是增加票数add
package com.example.user_votes;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.*;
@WebServlet("/add")
public class AddUserVotes extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//解析表单数据，获取要添加的用户信
// 解析请求
req.setCharacterEncoding("utf-8");
PrintWriter out = resp.getWriter();
//使用自己写的User类
User user = new User();
user.setId(Integer.parseInt(req.getParameter("id")));
user.setVotes(Integer.parseInt(req.getParameter("votes")));
// 连接数据库的操作
try {
// 1.加载驱动程序
String driver = "com.mysql.cj.jdbc.Driver";
Class.forName(driver).newInstance();
// 2.创建数据库连接
String url = "jdbc:mysql://localhost:3306/java_test?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC";
String jdbcuser = "root";
String jdbcpwd = "500400";
Connection conn = DriverManager.getConnection(url,jdbcuser,jdbcpwd);
// 3.创建语句对象
//静态的mysql操作语句
// Statement stmt = conn.createStatement();
// 4.执行sql
String sql = "UPDATE user_votes SET votes = ? WHERE id = ?";
PreparedStatement pstmt = conn.prepareStatement(sql);
//动态操作
int uservotes = user.getVotes() 1;
pstmt.setInt(1,uservotes);
pstmt.setInt(2,user.getId());
int rows = pstmt.executeUpdate();
// 5.处理结果
if(rows == 1){
System.out.println("add成功为:" uservotes);
}
else {
System.out.println("add失败！");
}
// 6.关闭语句对象，数据库连接
pstmt.clearBatch();
conn.close();
} catch (Exception e) {
System.out.println("添加用户失败" e.getMessage());
e.printStackTrace();
};
resp.setContentType("text/html;charset=UTF-8");
resp.getWriter().println("<script>alert('投票成功！');window.location.href='list';</script>");
//跳转到用户列表界面
resp.sendRedirect("list");
}
}减少票数
package com.example.user_votes;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
@WebServlet("/delete")
public class DeleteUserVotes extends HelloServlet{
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//解析表单数据，获取要添加的用户信
// 解析请求
req.setCharacterEncoding("utf-8");
PrintWriter out = resp.getWriter();
//使用自己写的User类
User user = new User();
user.setId(Integer.parseInt(req.getParameter("id")));
user.setVotes(Integer.parseInt(req.getParameter("votes")));
// 连接数据库的操作
try {
// 1.加载驱动程序
String driver = "com.mysql.cj.jdbc.Driver";
Class.forName(driver).newInstance();
// 2.创建数据库连接
String url = "jdbc:mysql://localhost:3306/java_test?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC";
String jdbcuser = "root";
String jdbcpwd = "500400";
Connection conn = DriverManager.getConnection(url,jdbcuser,jdbcpwd);
// 3.创建语句对象
//静态的mysql操作语句
// Statement stmt = conn.createStatement();
// 4.执行sql
String sql = "DELETE FROM user_votes WHERE id = ?";
PreparedStatement pstmt = conn.prepareStatement(sql);
//动态操作
pstmt.setInt(1,user.getId());
int rows = pstmt.executeUpdate();
// 5.处理结果
if(rows == 1){
System.out.println("delete成功为:" user.getId());
}
else {
System.out.println("delete失败！");
}
// 6.关闭语句对象，数据库连接
pstmt.clearBatch();
conn.close();
} catch (Exception e) {
System.out.println("添加用户失败" e.getMessage());
e.printStackTrace();
};
//跳转到用户列表界面
resp.sendRedirect("list");
}
}添加参与投票的
package com.example.user_votes;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
public class AddUser extends HelloServlet{
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//解析表单数据，获取要添加的用户信
// 解析请求
req.setCharacterEncoding("utf-8");
PrintWriter out = resp.getWriter();
//使用自己写的User类
User user = new User();
user.setName(req.getParameter("name"));
user.setUrl(req.getParameter("url"));
user.setVotes(0);
// 连接数据库的操作
try {
// 1.加载驱动程序
String driver = "com.mysql.cj.jdbc.Driver";
Class.forName(driver).newInstance();
// 2.创建数据库连接
String url = "jdbc:mysql://localhost:3306/java_test?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC";
String jdbcuser = "root";
String jdbcpwd = "500400";
Connection conn = DriverManager.getConnection(url,jdbcuser,jdbcpwd);
// 3.创建语句对象
//静态的mysql操作语句
// Statement stmt = conn.createStatement();
// 4.执行sql
String sql = "INSERT INTO user_votes(user_name,url,votes) VALUES(?,?,?)\n";
PreparedStatement pstmt = conn.prepareStatement(sql);
//动态操作
pstmt.setString(1,user.getName());
pstmt.setString(2,user.getUrl());
pstmt.setInt(3,user.getVotes());
int rows = pstmt.executeUpdate();
// 5.处理结果
if(rows == 1){
System.out.println("add成功为:" user.getName());
}
else {
System.out.println("add失败！");
}
// 6.关闭语句对象，数据库连接
pstmt.clearBatch();
conn.close();
} catch (Exception e) {
System.out.println("添加用户失败" e.getMessage());
e.printStackTrace();
};
//跳转到用户列表界面
resp.sendRedirect("list");
}
}该项目没有使用mvc项目结构，就是因为比较简单，因此如果有刚刚学习到这里的可以来看看，参考学习
附上项目目录图，其他的就没有过多的去介绍了，毕竟比较简单。
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持Devmax。