JavaMail - Need help creating multipart message/email!

I am trying to set a mime message with html and text as a multipart "alternative" message and add an attachment. I have the html stored in a string and the text stored in a string. I do not yet have the attachment, but I am assuming that I would just read this into a string also?!? Here is my code so far. I can send email with text or html, but not with both. What am I missing and where would I place the attachment? What import statements do I need to have (show current imports)?

import javax.swing.JOptionPane;
import java.util.*;
import javax.mail.*;
import javax.mail.event.*;
import javax.mail.internet.*;
import javax.activation.*;
import java.io.*;
...
MimeBodyPart textpart=new MimeBodyPart();
textpart.setText(text);
textpart.addHeaderLine("Content-Type: text/plain; charset=\"iso-8859-1\"");
textpart.addHeaderLine("Content-Transfer-Encoding: quoted-printable");

MimeBodyPart htmlpart=new MimeBodyPart();
htmlpart.setText(html,"text/html");
htmlpart.addHeaderLine("Content-Type: text/html; charset=\"iso-8859-1\"");
htmlpart.addHeaderLine("Content-Transfer-Encoding: quoted-printable");

Multipart mp=new MimeMultipart("related");
Multipart mp2=new MimeMultipart("alternative");

mp2.addBodyPart(textpart);
mp2.addBodyPart(htmlpart);

MimeBodyPart bp=new MimeBodyPart();
bp.setContent(mp);

mp.addBodyPart(bp);
message.setContent(mp);

...