Java开发简易投票系统实战教程

CREATE DATABASE vote_system;
USE vote_system;
CREATE TABLE options (
id INT PRIMARY KEY AUTO_INCREMENT,
option_name VARCHAR(100) NOT NULL,
vote_count INT DEFAULT 0
);

@WebServlet("/load")
public class LoadVoteServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        List options = new ArrayList<>();
        String sql = "SELECT * FROM options";
    try (Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/vote_system", "root", "password");
         PreparedStatement stmt = conn.prepareStatement(sql);
         ResultSet rs = stmt.executeQuery()) {

        while (rs.next()) {
            Option opt = new Option();
            opt.setId(rs.getInt("id"));
            opt.setName(rs.getString("option_name"));
            opt.setCount(rs.getInt("vote_count"));
            options.add(opt);
        }
    } catch (SQLException e) {
        e.printStackTrace();
    }

    request.setAttribute("options", options);
    request.getRequestDispatcher("vote.jsp").forward(request, response);
}
}

@WebServlet("/submit")
public class SubmitVoteServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
    // 防止重复提交
    HttpSession session = request.getSession();
    if (session.getAttribute("voted") != null) {
        response.sendRedirect("result");
        return;
    }

    int optionId = Integer.parseInt(request.getParameter("option"));

    String sql = "UPDATE options SET vote_count = vote_count + 1 WHERE id = ?";
    try (Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/vote_system", "root", "password");
         PreparedStatement stmt = conn.prepareStatement(sql)) {

        stmt.setInt(1, optionId);
        stmt.executeUpdate();

        // 标记已投票
        session.setAttribute("voted", "true");
    } catch (SQLException e) {
        e.printStackTrace();
    }

    response.sendRedirect("result");
}
}

  <% for (Option opt : options) { %>
    
    <%= opt.getName() %>

  <% } %>
  

投票结果
<% for (Option opt : options) { %>
  
<%= opt.getName() %> : <%= opt.getCount() %> 票
<% } %>