Zaawansowane szablony e-mail

/**
 * Demonstration of using JavaMail MIME message with the SparkPost RESTful interface
 */
public class App extends SparkPostBaseApp {
    public static void main(String[] args) throws Exception {
        Logger.getRootLogger().setLevel(Level.DEBUG);
        App app = new App();
        app.runApp();
    }
    private void runApp() throws Exception {
        Message message = createMultipartMessage();
        // Convert JavaMail message into a string for transmission
        String rfc822Content = getMessageAsString(message);
        // Add dynamic To and From using SparkPost substitution syntax
        rfc822Content = "To: {{address.email}}\r\nFrom: {{from}}\r\n" + rfc822Content;
        String fromAddress = getFromAddress();
        String[] recipients = getTestRecipients();
        sendEmail(fromAddress, recipients, rfc822Content);
    }
    private void sendEmail(String from, String[] recipients, String email)
            throws SparkPostException, IOException {
        Client sparkpostClient = newConfiguredClient();
        TransmissionWithRecipientArray transmission = new TransmissionWithRecipientArray();
        // Populate Recipients
        List<RecipientAttributes> recipientArray = new ArrayList<>();
        for (String recipient : recipients) {
            RecipientAttributes recipientAttribs = new RecipientAttributes();
            recipientAttribs.setAddress(new AddressAttributes(recipient));
            recipientArray.add(recipientAttribs);
        }
        transmission.setRecipientArray(recipientArray);
        transmission.setReturnPath(from);
        // Populate Substitution Data
        Map<String, String> substitutionData = new HashMap<>();
        substitutionData.put("from", from);
        substitutionData.put("name", "Your Name Here");
        transmission.setSubstitutionData(substitutionData);
        // Populate Email Body with RFC822 MIME
        TemplateContentAttributes contentAttributes = new TemplateContentAttributes();
        contentAttributes.setEmailRFC822(email);
        transmission.setContentAttributes(contentAttributes);
        // Send Email
        RestConnection connection = new RestConnection(sparkpostClient, getEndPoint());
        Response response = ResourceTransmissions.create(connection, 0, transmission);
        if (response.getResponseCode() == 200) {
            System.out.println("✅ Transmission Response: " + response);
        } else {
            System.err.println("❌ TRANSMISSION ERROR: " + response);
        }
    }
    /**
     * Builds an email with text, HTML, and attachment parts
     */
    private Message createMultipartMessage() throws MessagingException {
        Properties props = new Properties();
        props.put("mail.smtp.host", "none"); // Required for JavaMail to work
        Session session = Session.getDefaultInstance(props, null);
        Message message = new MimeMessage(session);
        message.setSubject("A multipart MIME message demo");
        // Main multipart container
        Multipart multiPart = new MimeMultipart("mixed");
        // Sub multipart for text + HTML
        MimeMultipart altPart = new MimeMultipart("alternative");
        // Text part
        MimeBodyPart textPart = new MimeBodyPart();
        textPart.setText("{{name}},\r\nplain text content", "utf-8");
        // HTML part
        MimeBodyPart htmlPart = new MimeBodyPart();
        htmlPart.setContent("<b>{{name}},<br><br>Our HTML content</b>", "text/html; charset=utf-8");
        // Add text and HTML to the alternative container
        altPart.addBodyPart(textPart);
        altPart.addBodyPart(htmlPart);
        // Wrap alternative part in a MimeBodyPart so it can be added to mixed container
        MimeBodyPart altBodyPart = new MimeBodyPart();
        altBodyPart.setContent(altPart);
        // Add alternative section to mixed container
        multiPart.addBodyPart(altBodyPart);
        // Add attachment
        MimeBodyPart attachmentPart = new MimeBodyPart();
        String filename = "java_SparkPost_background.pdf";
        DataSource source = new FileDataSource(filename);
        attachmentPart.setDataHandler(new DataHandler(source));
        attachmentPart.setFileName(filename);
        multiPart.addBodyPart(attachmentPart);
        // Set full content
        message.setContent(multiPart);
        return message;
    }
    /**
     * Converts a JavaMail message into an RFC822 string
     */
    private String getMessageAsString(Message msg) throws IOException, MessagingException {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        try {
            msg.writeTo(out);
            return out.toString("UTF-8");
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException("UTF-8 not found! " + e.getMessage());
        } finally {
            try {
                out.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}