使用Javamail将图像作为附件发送

Question

I'm trying to send an image using Javamail as an attachment without having an actual image saved in the file system. Instead I have a Base64 encoded string.

public void sendMultiPartMailWithAttachments(final String[] recipient, final String from,
        @Nullable final String replyTo, @Nullable final String replyToName, final String subject,
        final String plainText, final String html, String image)
        throws MessagingException, AddressException, UnsupportedEncodingException {
    Message msg = this.setupMessage(recipient, from, replyTo, replyToName, subject);

    // Create the text part
    MimeBodyPart textPart = new MimeBodyPart();
    textPart.setText(plainText, "utf-8");

    MimeBodyPart htmlPart = new MimeBodyPart();
    htmlPart.setContent(html, "text/html; charset=utf-8");

    byte[] bytes = Base64.getMimeDecoder().decode(image);
    MimeBodyPart imagePart = new MimeBodyPart();
    // imagePart.setDataHandler(new DataHandler(imageObject, "image/jpeg"));
    imagePart.setDataHandler(new DataHandler(new ByteArrayDataSource(bytes, MediaType.JPEG.toString())));
    imagePart.setFileName("proof_test.jpg");

    Multipart multiPart = new MimeMultipart("alternative");
    multiPart.addBodyPart(textPart);
    multiPart.addBodyPart(htmlPart);
    multiPart.addBodyPart(imagePart);

    msg.setContent(multiPart);

    msg.saveChanges();

    Transport.send(msg);
}

I'm able to receive an email fine but when I do the attachment is unable to be opened.

Also, when I use getContentType() it displays text/plain as opposed to image/jpeg .

Answer 1

Unless the image is exactly an image of what's in the text part, you don't want it to be part of the same multipart/alternative. Instead, you want an outer multipart/mixed, the first part of which is the multipart/alternative, and the second part of which is the image/jpeg.

If the image string is already base64 encoded, you'll want to use a PreencodedMimeBodyPart when adding it to the multipart/mixed. But it looks like you're decoding it first, which will then allow JavaMail to re-encode it. That should work as well, but is less efficient.

If you fix all this and still don't get the correct content type for the image, use Message.writeTo to write the image to a FileOutputStream, and then post the output here.