How to Send Email with Attachments Using Google App Engine

The cool thing about Google App Engine is that you can send e-mails from there for free (well, up to 2000 per day). You can even send attachments with it!

How do you do that? Here is a code snippet. Note that two cases are dealt here, one when there are attachments (so a multi part message is created) and the simplest case where there no attachments:

private static String SendEmail(String user, String to,

    String cc, String subject, String body, String filename,

    String mimeType, byte[] rawData)

{

    Properties props = new Properties();

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

    MimeMessage message = new MimeMessage(session);

    try {

        message.setFrom(new InternetAddress(user));

        message.addRecipient(Message.RecipientType.TO,

                             new InternetAddress(to));

        if (cc != null && !cc.trim().isEmpty()) {

              message.addRecipient(Message.RecipientType.CC,

                             new InternetAddress(cc));                    

        }

        message.setSubject(subject, "UTF-8");

        if (rawData != null && filename != null &&

           !filename.isEmpty()) {

             if (mimeType == null || mimeType.isEmpty()) {

                 mimeType = GetMimeType(filename);

             }

             Multipart mp = new MimeMultipart();

             MimeBodyPart htmlPart = new MimeBodyPart();

             htmlPart.setContent(body, "text/html");

             mp.addBodyPart(htmlPart);

             ByteArrayDataSource dataSource = new

                 ByteArrayDataSource(rawData, mimeType);

     

             MimeBodyPart attachment = new MimeBodyPart();

             attachment.setFileName(filename);

             attachment.setDataHandler(

                 new DataHandler(dataSource));                                  

             mp.addBodyPart(attachment);

             message.setContent(mp);

         }

         else {

             message.setText(body, "UTF-8");

         }

         Transport.send(message);

     } catch (Exception e) {

          return "Error: " + e.getMessage();

     } 

     return "ok";

}