在 MimeMessage 内容中设置按钮事件 - Java Servlet

Question

我试图通过发送包含一个按钮的电子邮件来创建注册确认，该按钮必须允许（仅在按下时）将数据（姓名、姓氏、电子邮件和密码）插入到 MySQL 数据库中。 我想了解 MimeMessage 内容中的按钮是否已被按下。 使用“按钮标签”或“标签”来做到这一点更好吗？ 有没有其他方法可以做我想做的事？ 我试过这段代码（插入方法显然用于将数据插入表中，应该在按下 MimeMessage 内容中的“链接”按钮时调用），但它不起作用：

package com.wallet.walletcontrol;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.Properties;

@WebServlet(name = "RegisterServlet", value = "/register")
public class RegisterServlet extends HttpServlet {

public static String firstName = "", lastName = "", email = "", inputPassword = "", repeatPassword = "";

public static void insert() {
    try {
        Class.forName("com.mysql.cj.jdbc.Driver");
        Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/wallet", "root", "1234");
        String query = "INSERT INTO users (email, name, surname, password) VALUES (?, ?, ?, ?)";
        PreparedStatement statement = connection.prepareStatement(query);
        statement.setString(1, email);
        statement.setString(2, firstName);
        statement.setString(3, lastName);
        String cipherPass = PasswordManager.createHash(inputPassword);
        statement.setString(4, cipherPass);
        statement.executeUpdate();
    }
    catch (MessagingException | SQLException | ClassNotFoundException e) {}
}

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    firstName = request.getParameter("firstName");
    lastName = request.getParameter("lastName");
    email = request.getParameter("inputEmail");
    inputPassword = request.getParameter("inputPassword");
    repeatPassword = request.getParameter("repeatPassword");

    Properties properties = System.getProperties();
    properties.put("mail.smtp.auth", "true");
    properties.put("mail.smtp.starttls.enable", "true");
    properties.put("mail.smtp.port", "587");
    properties.put("mail.smtp.host", "smtp.gmail.com");

    Session messageSession = Session.getDefaultInstance(properties, new Authenticator() {
        protected PasswordAuthentication getPasswordAuthentication() {
            return new PasswordAuthentication("francoarmani2008@gmail.com", "Francoarmani98");
        }
    });

    if(inputPassword.equals(repeatPassword)){
        try {
            MimeMessage mimeMessage = new MimeMessage(messageSession);
            mimeMessage.setFrom(new InternetAddress(email));
            mimeMessage.setRecipient(Message.RecipientType.TO, new InternetAddress(email));
            mimeMessage.setSubject("Password recovery");

            mimeMessage.setContent("<form method='post' action='http://localhost:8080/WalletControl_war_exploded/login.jsp'><button name='link' id='link'>Confirm registration</button></form>", "text/html; charset=utf-8");
          // this a variable always contains (if I print it) null value
            String a = request.getParameter("link");
            Transport.send(mimeMessage);
        } catch (MessagingException e) {
            e.printStackTrace();
        }
        request.setAttribute("nameNewUser",firstName);
        request.getServletContext().getRequestDispatcher("/registerSuccess.jsp" ).include(request,response);
    }
    else{
        request.getServletContext().getRequestDispatcher("/passwordDif.jsp" ).include(request,response);
    }
}

}