mình có file html nhập thông tin này
// index.html

<form action="/emailList" method="post">
    <input type="hidden" name="action" value="add">
    <label class="pad_top">Email:</label>
    <input type="email" name="email" ><br>
    <label class="pad_top">First Name:</label>
    <input type="text" name="firstName" ><br>
    <label class="pad_top">Last Name:</label>
    <input type="text" name="lastName"><br>
    <label>&nbsp;</label>
    <input type="submit" value="Join Now">
</form> ```

file servlet để xử lí

@WebServlet(name = “EmailListServlet”)
public class EmailListServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    String url = "/index.jsp";
    String action = request.getParameter("action");

    if (action == null) {
        action = "join";
        System.out.println("clicked return button");
    }

    if (action.equals("join")) {
        url = "/index.jsp";
    }
    else if (action.equals("add")) {
        String firstName = request.getParameter("firstName");
        String lastName = request.getParameter("lastName");
        String email = request.getParameter("email");

        User user = new User(firstName, lastName,  email);
            url = "/thanks.jsp";

        request.setAttribute("user", user);
    }
    getServletContext()
            .getRequestDispatcher(url)
            .forward(request, response);
}


protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

}

}

file thank.jsp để hiện ra kết quả

Thanks for joining our email list

Here is the information that you entered:

Email:
${user.email}

First Name:
${user.firstName}

Last Name:
${user.lastName}

To enter another email address, click on the Back button in your browser or the Return button shown below.

<(form action="" method=“post”>
<(input type=“submit” value=“Return”>