Our goals

Our example application will be sending five types of emails:

1. Text (non-HTML) email.
2. Simple HTML (with internationalized greeting).
3. HTML text with an attachment.
4. HTML text with an inline image.
5. HTML text edited by the user.

Spring configuration

In order to process our templates, we will configure a TemplateEngine especially configured for email processing, in our Spring Email configuration:

@Configuration
@PropertySource("classpath:mail/emailconfig.properties")
public class SpringMailConfig implements ApplicationContextAware, EnvironmentAware {

    ...

    @Bean
    public ResourceBundleMessageSource emailMessageSource() {
        final ResourceBundleMessageSource messageSource = new ResourceBundleMessageSource();
        messageSource.setBasename("mail/MailMessages");
        return messageSource;
    }

    ...

    @Bean
    public TemplateEngine emailTemplateEngine() {
        final SpringTemplateEngine templateEngine = new SpringTemplateEngine();
        // Resolver for TEXT emails
        templateEngine.addTemplateResolver(textTemplateResolver());
        // Resolver for HTML emails (except the editable one)
        templateEngine.addTemplateResolver(htmlTemplateResolver());
        // Resolver for HTML editable emails (which will be treated as a String)
        templateEngine.addTemplateResolver(stringTemplateResolver());
        // Message source, internationalization specific to emails
        templateEngine.setTemplateEngineMessageSource(emailMessageSource());
        return templateEngine;
    }

    private ITemplateResolver textTemplateResolver() {
        final ClassLoaderTemplateResolver templateResolver = new ClassLoaderTemplateResolver();
        templateResolver.setOrder(Integer.valueOf(1));
        templateResolver.setResolvablePatterns(Collections.singleton("text/*"));
        templateResolver.setPrefix("/mail/");
        templateResolver.setSuffix(".txt");
        templateResolver.setTemplateMode(TemplateMode.TEXT);
        templateResolver.setCharacterEncoding(EMAIL_TEMPLATE_ENCODING);
        templateResolver.setCacheable(false);
        return templateResolver;
    }

    private ITemplateResolver htmlTemplateResolver() {
        final ClassLoaderTemplateResolver templateResolver = new ClassLoaderTemplateResolver();
        templateResolver.setOrder(Integer.valueOf(2));
        templateResolver.setResolvablePatterns(Collections.singleton("html/*"));
        templateResolver.setPrefix("/mail/");
        templateResolver.setSuffix(".html");
        templateResolver.setTemplateMode(TemplateMode.HTML);
        templateResolver.setCharacterEncoding(EMAIL_TEMPLATE_ENCODING);
        templateResolver.setCacheable(false);
        return templateResolver;
    }

    private ITemplateResolver stringTemplateResolver() {
        final StringTemplateResolver templateResolver = new StringTemplateResolver();
        templateResolver.setOrder(Integer.valueOf(3));
        // No resolvable pattern, will simply process as a String template everything not previously matched
        templateResolver.setTemplateMode("HTML5");
        templateResolver.setCacheable(false);
        return templateResolver;
    }

    ...

}

Note that we have configured three template resolvers for our email-specific engine: one for the TEXT templates, another one for HTML templates, and a third one for editable HTML templates, which we will give the user the opportunity to modify and will reach the template engine as a mere String once modified.

All three template resolvers are ordered so that they execute in sequence, trying to match their resolvable patterns against the name of the template and only resolving the specified template if its name matches.

Also note how this TemplateEngine is specific to email processing, and completely separate to the one used for the web interface. This TemplateEngine for the web interface, which will be integrated with Spring MVC by means of a ThymeleafViewResolver is in fact defined in a different @Configuration file extending WebMvcConfigurerAdapter (and which we will not show here in order to focus on email processing).

Executing the Template Engine

At some point in our code, we will need to execute our template engine in order to create the text of our messages. We have chosen to do this in an EmailService class, so that it stays clear that we consider this a responsibility of our business layer (and not the web layer).

As usual in Thymeleaf, before executing we will need to populate a context containing all the variables we want to use during template execution. Given the fact that our email processing is not web-dependent, an instance of Context will do:

final Context ctx = new Context(locale);
ctx.setVariable("name", recipientName);
ctx.setVariable("subscriptionDate", new Date());
ctx.setVariable("hobbies", Arrays.asList("Cinema", "Sports", "Music"));
ctx.setVariable("imageResourceName", imageResourceName); // so that we can reference it from HTML

final String htmlContent = this.templateEngine.process("html/email-inlineimage.html", ctx);

Our email-inlineimage.html is the template file we will use for sending emails with an inlined image, and it looks like:

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
  <head>
    <title th:remove="all">Template for HTML email with inline image</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
  </head>
  <body>
    <p th:text="#{greeting(${name})}">
      Hello, Peter Static!
    </p>
    <p th:if="${name.length() > 10}">
      Wow! You've got a long name (more than 10 chars)!
    </p>
    <p>
      You have been successfully subscribed to the <b>Fake newsletter</b> on
      <span th:text="${#dates.format(subscriptionDate)}">28-12-2012</span>
    </p>
    <p>Your hobbies are:</p>
    <ul th:remove="all-but-first">
      <li th:each="hobby : ${hobbies}" th:text="${hobby}">Reading</li>
      <li>Writing</li>
      <li>Bowling</li>
    </ul>
    <p>
      You can find <b>your inlined image</b> just below this text.
    </p>
    <p>
      <img src="sample.png" th:src="|cid:${imageResourceName}|" />
    </p>
    <p>
      Regards, <br />
      <em>The Thymeleaf Team</em>
    </p>
  </body>
</html>

Let’s remark some points:

• The former template is fully WYSIWYG; you can check how it looks just by opening it with your browser. That’s much better than sending an email to see the result, isn’t it?

• We can use all Thymeleaf features. Here for example we have used i18n with a parameterized #{...} expression, th:each to iterate over a list, #dates to format a date…
• The img element has a hardcoded src value —nice for prototyping—, which will be substituted at runtime by something like cid:image.jpg matching the attached image filename.

Text (non-HTML) email

And what about text email? Well, we have already configured a template resolver for textual email templates, so all we would have to do is create template using Thymeleaf’s textual syntax, just like:

[( #{greeting(${name})} )]

[# th:if="${name.length() gt 10}"]Wow! You've got a long name (more than 10 chars)![/]

You have been successfully subscribed to the Fake newsletter on [( ${#dates.format(subscriptionDate)} )].

Your hobbies are:
[# th:each="hobby : ${hobbies}"]
 - [( ${hobby} )]
[/]

Regards,
    The Thymeleaf Team

The service class

Finally, let’s see how the method executing this email template at our EmailService service class would look like:

public void sendMailWithInline(
  final String recipientName, final String recipientEmail, final String imageResourceName,
  final byte[] imageBytes, final String imageContentType, final Locale locale)
  throws MessagingException {

    // Prepare the evaluation context
    final Context ctx = new Context(locale);
    ctx.setVariable("name", recipientName);
    ctx.setVariable("subscriptionDate", new Date());
    ctx.setVariable("hobbies", Arrays.asList("Cinema", "Sports", "Music"));
    ctx.setVariable("imageResourceName", imageResourceName); // so that we can reference it from HTML

    // Prepare message using a Spring helper
    final MimeMessage mimeMessage = this.mailSender.createMimeMessage();
    final MimeMessageHelper message =
        new MimeMessageHelper(mimeMessage, true, "UTF-8"); // true = multipart
    message.setSubject("Example HTML email with inline image");
    message.setFrom("[email protected]");
    message.setTo(recipientEmail);

    // Create the HTML body using Thymeleaf
    final String htmlContent = this.templateEngine.process("email-inlineimage.html", ctx);
    message.setText(htmlContent, true); // true = isHtml

    // Add the inline image, referenced from the HTML code as "cid:${imageResourceName}"
    final InputStreamSource imageSource = new ByteArrayResource(imageBytes);
    message.addInline(imageResourceName, imageSource, imageContentType);

    // Send mail
    this.mailSender.send(mimeMessage);

}

Note that we have used an org.springframework.core.io.ByteArrayResource object to attach the image uploaded by the user, which we previously converted into a byte[].

You could also make use of FileSystemResource to attach a file directly from the filesystem —thus avoiding loading it into memory—, or UrlResource to attach a remote file.

The controller

Now for the controller method that calls our service:

/*
* Send HTML mail with inline image
*/
@RequestMapping(value = "/sendMailWithInlineImage", method = RequestMethod.POST)
public String sendMailWithInline(
  @RequestParam("recipientName") final String recipientName,
  @RequestParam("recipientEmail") final String recipientEmail,
  @RequestParam("image") final MultipartFile image,
  final Locale locale)
  throws MessagingException, IOException {

    this.emailService.sendMailWithInline(
        recipientName, recipientEmail, image.getName(),
        image.getBytes(), image.getContentType(), locale);
    return "redirect:sent.html";

}

Cannot be easier. Note how we use a Spring MVC MultipartFile object to model the uploaded file and pass its contents on to the service.