您的问题不是很清楚。让我弄清需求吧；您只需要成功注册即可将代码发送给用户的代码。正确？

在您的servlet（在Submit操作中调用）中，

if(user input is valid){
  Step1: registerUser();
  Step2: send confirmationEmail();
} else {
  Step3: Exception case
}

发送电子邮件方法理想情况下会将请求发送到JMS（队列），以将电子邮件发送给所需的用户。以下是发送电子邮件的代码段。

//Sample java code to send email

public void sendEmail(){

        try{

            Properties props = null;

                if (props == null) {
                        props = System.getProperties();
                }

                props.put("mail.smtp.host", "<server host name>");

                Session session = Session.getInstance(props, null);

                MimeMessage message = new MimeMessage(session);

                message.setFrom(new InternetAddress("<from email id>"));

                message.addRecipients(Message.RecipientType.CC, "<Registered user email id>");

                message.setSubject("<Subject of the email>");

                message.setContent("<Content of the email>", "text/plain");

                Transport.send(message);

                    logger.info("Sent Email :" + 
                        "From :" + message.getFrom() +
                        "To:" + message.getAllRecipients() +
                        "Subject:" + message.getSubject() );

            } catch(Exception ex){
                ex.printStackTrace();
            }       
        }