在Java中如何开发简易投票系统_投票系统项目实战解析

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

@WebServlet("/load")
public class LoadVoteServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        List<Option> options = new ArrayList<>();
        String sql = "SELECT * FROM options";
<pre class='brush:java;toolbar:false;'>    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 {
<pre class='brush:java;toolbar:false;'>    // 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");
}

<form action="submit" method="post">
  <% for (Option opt : options) { %>
    <input type="radio" name="option" value="<%= opt.getId() %>" required>
    <label><%= opt.getName() %></label><br>
  <% } %>
  <input type="submit" value="投票">
</form>

<h2>投票结果</h2>
<% for (Option opt : options) { %>
  <p><%= opt.getName() %> : <%= opt.getCount() %> 票</p>
<% } %>