是否可以将内联位图对象添加到通过JavaMail发送的电子邮件的正文中？

Question

我想将内嵌位图（在代码内生成）添加到要通过Android中的JavaMail发送的电子邮件中。以下是我当前的代码：

try {
            // Compose the message
            // javax.mail.internet.MimeMessage class is
            // mostly used for abstraction.
            Message message = new MimeMessage(session);

            // header field of the header.
            message.setFrom(new InternetAddress("[email protected]"));

            message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(recipient));
            message.setSubject("Workside Verification Service");
            message.setText(
                    "Thank you for registering. Please click on the following link to activate your account:\n\n"
                            + urlWithToken
                            + "\n\nRegards,\nThe Workside Team");

            // Add the generated QR code bitmap here
            Multipart multipart = new MimeMultipart("related");
            MimeBodyPart imgPart = new MimeBodyPart();
            // imageFile is the file containing the image

            // TODO - pass bitmap to imageFile below
            File file = new File(null);
            OutputStream os = new BufferedOutputStream(new FileOutputStream(file));

            mBitmapQR.compress(Bitmap.CompressFormat.PNG, 90, os);


            imgPart.attachFile(imageFile);
            multipart.addBodyPart(imgPart);
            message.setContent(multipart);

            Transport.send(message); // send Message

            System.out.println("Email Sent");

        } catch (MessagingException | FileNotFoundException e) {
            throw new RuntimeException(e);
        }

我曾考虑将位图转换为File对象，然后将其添加到消息的正文中，但是我认为可能会有更直接，更有效的方法。

Answer 1

“雅加达邮件常见问题解答是您最好的资源。参见How do I send HTML mail that includes images?。描述了3个选择：

1. 将图像链接到网站，我怀疑这对您有用。
2. 插入图像<img src="data:image/jpeg;base64,base64-encoded-data-here" />
3. 正在构造多部分/相关消息。

Answer 2

从代码中可以看出，问题是我将文本添加到多部分中，然后是图像（有效地覆盖了文本），然后将多部分分配给了消息。解决方法是使用addBodyPart(text)添加文本，然后使用addBodyPart(image)。之后，我可以使用setContent(multipart)将文本和图像正确分配给电子邮件。

    // Add the generated QR code bitmap here
    Multipart multipart = new MimeMultipart("related");
    MimeBodyPart imgPart = new MimeBodyPart();

    // Set the cache path and generate the new file image
    String mFilePath = mContext.getCacheDir().toString();
    File file = new File(mFilePath, FILE_NAME);
    OutputStream os = new BufferedOutputStream(new FileOutputStream(file));

    // TITLE
    message.setSubject("Workside Verification Service");
    // TEXT
    MimeBodyPart txtPart = new MimeBodyPart();
    txtPart.setContent("Welcome to Workside! \n\nPlease proceed by scanning the QR code provided using the Workside application available in the Google Play store.\n\n\n"
                                + "Regards,\n\nThe Workside Team", "text/plain");
    // ADD TEXT
    multipart.addBodyPart(txtPart);
    // Generate image using the QR Bitmap, and attach it
    mBitmapQR.compress(Bitmap.CompressFormat.JPEG, 90, os);
    imgPart.attachFile(mFilePath + FILE_NAME);
    // ADD IMAGE
    multipart.addBodyPart(imgPart);
    message.setContent(multipart);