Question

We are developing a simple web application in JSF in which there is a need to include a “forget password” module. For the sake of demonstration and simplicity, I tried the following code in Java Servlet. It can send a mail to Gmail and works just fine there is no problem at all. The following is the complete Servlet code.

public class MailClient extends HttpServlet {

    private class SMTPAuthenticator extends Authenticator {

        private PasswordAuthentication authentication;

        public SMTPAuthenticator(String login, String password) {
            authentication = new PasswordAuthentication(login, password);
        }

        @Override
        protected PasswordAuthentication getPasswordAuthentication() {
            return authentication;
        }
    }

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

        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        try {
            String from = "[e-mail]";
            String to = "[e-mail]";
            String subject = "A mail from Java.";
            String message = "My first mail from Java.";
            String login = "[e-mail]";
            String password = "password";

            Properties props = new Properties();
            props.setProperty("mail.host", "smtp.gmail.com");
            props.setProperty("mail.smtp.port", "587");
            props.setProperty("mail.smtp.auth", "true");
            props.setProperty("mail.smtp.starttls.enable", "true");

            Authenticator auth = new SMTPAuthenticator(login, password);
            Session session = Session.getInstance(props, auth);
            MimeMessage msg = new MimeMessage(session);

            try {
                msg.setText(message);
                msg.setSubject(subject);
                msg.setFrom(new InternetAddress(from));
                msg.addRecipient(Message.RecipientType.TO,
                        new InternetAddress(to));
                Transport.send(msg);
            } catch (MessagingException ex) {
                Logger.getLogger(MailClient.class.getName()).
                        log(Level.SEVERE, null, ex);
            }
        } finally {
            out.close();
        }
    }

    @Override
    protected void doGet(HttpServletRequest request,
        HttpServletResponse response) throws ServletException, IOException {
        processRequest(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request,
        HttpServletResponse response) throws ServletException, IOException {
        processRequest(request, response);
    }

    @Override
    public String getServletInfo() {
        return "Short description";
    }
}

---

Now, the first question is that as soon as a user enters his valid email address, a verification code should be submitted to a specific message server (Gmail, Yahoo and so on) without asking the user for his password (Which is not the case of the above code) which is essential in implementing the “forget password” module in a web application.

The second question is that the above code is bound to sending a mail only to Gmail. If I want to send a mail to some other message server say Yahoo, the statement

props.setProperty("mail.host", "smtp.gmail.com");

needs to be changed to

props.setProperty("mail.host", "smtp.mail.yahoo.com"); 

[and port no too, regarding others] means that a specific message server to which a message has to be sent need to be recognized properly. Which is the best way to do so?. What is the best method(s) to overcome these issues, please.

Answer 1

Do you change your SMTP settings in your email client each time you send a mail to a different mail provider? No. You don’t set the SMTP server to gmail when sending a mail to a gmail.com address. And then set it to yahoo when sending a mail to a yahoo.com address. You set it to your email provider SMTP server, and this SMTP server sends the mail to the appropriate location.

Just choose an SMTP server which agrees to send mails from your application. Sending a dozen per day will be OK with any SMTP provider. But if you send thousands a day, then you could have problems with your provider. Just ask your hosting provider how it goes with outgoing mails (how much it costs, how many per day are accepted, is there a bandwidth limit, etc.)