How to Improve Design for HTML, Plain Text and Multiple Recipients?

Question

Hello there,
JavaMail programming is so fun! I first start off mixing the JavaMail code inside a servlet and then refactored it to two separate classes.
Mailer is the independent class which uses JNDI to look up config parameters, sends e-mails, and then closes the connection with the protocol.
public class Mailer {
     private Session mailSession;
     protected void sendMsg(String email, String subject, String body)
     throws MessagingException, NamingException {
          Properties props = new Properties();
          InitialContext ictx = new InitialContext(props);
          Session mailSession = (Session) ictx.lookup("java:/Mail");
          String username = (String) props.get("mail.smtps.user");
          String password = (String) props.get("mail.smtps.password");
          MimeMessage message = new MimeMessage(mailSession);
          message.setSubject(subject);
          message.setRecipients(javax.mail.Message.RecipientType.TO,
                    javax.mail.internet.InternetAddress.parse(email, false));
          message.setText(body);
          message.saveChanges();
          Transport transport = mailSession.getTransport("smtps");
          try {
               transport.connect(username, password);
               transport.sendMessage(message, message.getAllRecipients());
               Logger.getLogger(this.getClass()).warn("Message sent");
          finally {
               transport.close();
}MailController is just a simple Java servlet where a Mailer object is instantiated and a String is passed inside the Mailer.sendMsg() method.
public class MailController extends HttpServlet {
     /** static final HTML setting for content type */
     private static final String HTML = "text/html";
     myapp/** static final HTML setting for content type */
     private static final String PLAIN = "text/plain";
     public void doGet(HttpServletRequest request, HttpServletResponse response)
     throws ServletException, IOException {
          doPost(request, response);
     public void doPost(HttpServletRequest request, HttpServletResponse response)
     throws ServletException, IOException {
          response.setContentType(PLAIN);
          PrintWriter out = response.getWriter();
          String mailToken = TokenUtil.getEncryptedKey();
          String body = "Hello there, " + "\n\n"
                    + "Wanna play a game of golf?" + "\n\n"
                 + "Please confirm: https://localhost:8443/myapp/confirm?token="
                 + mailToken + "\n\n" + "-Golf USA";
          Mailer mailer = new Mailer();
          try {
               mailer.sendMsg("[email protected]", "Golf Invitation!", body);
               out.println("Message Sent");
          catch (MessagingException e) {
               e.printStackTrace();
          catch (NamingException e) {
               e.printStackTrace();
}Have some design issues...
If you can notice, I manually place the body of the e-mail (as a String) from inside the client (in this case, a Java Servlet). Also, I manually have to switch the content type inside the doPost().
Question(s):
(1) How can the Mailer class be set up, so it can send both HTML and plain text messages?
(2) How can the Mailer class be structured to send e-mail to multiple recipients or one user?
(3) Would both of these features / actions require writing two overloaded methods for sendMsg()?
Would appreciate it if someone could help me...
Happy programming,
Michael

Answer 1

Okay, I came up with this single method:
Mailer.java:
public class Mailer
     private Session mailSession;
     protected void sendMessage(String email, String recipient, String subject,
               String plainText, String htmlText)
        throws MessagingException, NamingException
          Properties props = new Properties();
          InitialContext ictx = new InitialContext(props);
          Session mailSession = (Session) ictx.lookup("java:/Mail");
          String username = (String) props.get("mail.smtps.user");
          String password = (String) props.get("mail.smtps.password");
          MimeMessage message = new MimeMessage(mailSession);
          InternetAddress from = new InternetAddress(email);
          InternetAddress to = new InternetAddress(recipient);
          message.setSubject(subject);
          message.setFrom(from);
          message.addRecipient(Message.RecipientType.TO, to);
          Multipart multipart = new MimeMultipart();
          BodyPart messageBodyPart = new MimeBodyPart();
          messageBodyPart.setText(plainText);
          multipart.addBodyPart(messageBodyPart);
          messageBodyPart = new MimeBodyPart();
          messageBodyPart.setContent(htmlText, "text/html");
          multipart.addBodyPart(messageBodyPart);
          message.setContent(multipart);
          Transport transport = mailSession.getTransport("smtps");
          try {
               transport.connect(username, password);
               transport.sendMessage(message, message.getAllRecipients());
               Logger.getLogger(this.getClass()).info("Message sent");
          catch (Throwable t) {
               Logger.getLogger(this.getClass()).error("Unable to Send Message");
               t.printStackTrace();
          finally {
               transport.close();
}Created a MailController class to instantiate and run the Mailer class.
public class MailController extends HttpServlet {
     // doPost() method()
     public void doPost(HttpServletRequest request, HttpServletResponse response)
     throws ServletException, IOException {
          response.setContentType(PLAIN);
          PrintWriter out = response.getWriter();
          String mailToken = TokenUtil.getEncryptedKey();
          String plainText = "Hello there, " + "\n\n"
                    + "I wanna invite you to a game of golf!" + "\n\n"
     + "Please confirm: https://localhost:8443/myapp/confirm?token="
                    + mailToken + "\n\n" + "-Golf USA";
          String htmlText = "<H1>Golfer Challenge!</H1>";
          Mailer mailer = new Mailer();
          try {
               String from = "[email protected]";
               String recipient = "[email protected]";
               String subject = "Golf Challenge";
               mailer.sendMessage(from, recipient, subject, plainText, htmlText);
               Logger.getLogger(
                           this.getClass()).info("Message Sent to: " + recipient
                                                          + " from: " + email);
               out.println("Message Sent to: " +
                                         recipient + "\n" + " from: " + email);
          catch (MessagingException e) {
               e.printStackTrace();
          catch (NamingException e) {
               e.printStackTrace();
}Question(s):
(1) How come the Multipart Alternative only supports HTML for the second part? Can I specify it to send HTML first and plainText second?
(2) How would I send in multiple recipients? Would I have to pass in an array reference (surrounded by a for loop) inside sendMessage() as follows:
mailer.sendMessage(from, myArray, subject, plainText, htmlText);
Thank you for all of your help!
-Michael