Sending HTML email with Spring Boot and Thymeleaf

Question

I am checking out how to send an email using Spring Boot. Send an e-mail using standard Spring Boot modules and prepare HTML content for a message using Thymeleaf template engine. This is the dependencies I use

 <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-mail</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.icegreen</groupId>
            <artifactId>greenmail</artifactId>
            <version>1.5.0</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <!-- Import dependency management from Spring Boot -->
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${spring-boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

Here my MailClient

@Service
public class MailClient {

    private JavaMailSender mailSender;
    private MailContentBuilder mailContentBuilder;

    @Autowired
    public MailClient(JavaMailSender mailSender, MailContentBuilder mailContentBuilder) {
        this.mailSender = mailSender;
        this.mailContentBuilder = mailContentBuilder;
    }

    public void prepareAndSend(String recipient, String message) {
        MimeMessagePreparator messagePreparator = mimeMessage -> {
            MimeMessageHelper messageHelper = new MimeMessageHelper(mimeMessage);
            messageHelper.setFrom("amadeu.cabanilles@gmail.com");
            messageHelper.setTo("amadeu.cabanilles@gmail.com");
            messageHelper.setSubject("Sample mail subject");
            String content = mailContentBuilder.build(message);
            messageHelper.setText(content, true);
        };
        try {
            mailSender.send(messagePreparator);
        } catch (MailException e) {
            e.printStackTrace();
        }
    }
}

This is my Test Class

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(Application.class)
public class MailClientTest {

    @Autowired
    private MailClient mailClient;

    private GreenMail smtpServer;

    @Before
    public void setUp() throws Exception {
        smtpServer = new GreenMail(new ServerSetup(25, null, "smtp"));
        smtpServer.start();
    }

    @Test
    public void shouldSendMail() throws Exception {
        //given
        String recipient = "amadeu.cabanilles@gmail.com";
        String message = "Test message content";
        //when
        mailClient.prepareAndSend(recipient, message);
        //then
        String content = "<span>" + message + "</span>";
        assertReceivedMessageContains(content);
    }

    private void assertReceivedMessageContains(String expected) throws IOException, MessagingException {
        MimeMessage[] receivedMessages = smtpServer.getReceivedMessages();
        assertEquals(1, receivedMessages.length);
        String content = (String) receivedMessages[0].getContent();
        System.out.println(content);
        assertTrue(content.contains(expected));
    }

    @After
    public void tearDown() throws Exception {
        smtpServer.stop();
    }
}

Executing the Test in my computer is OK, I pass the test but I don't receive any email.

Answer 1

You don't receive any email because this integration test uses local testing SMTP server stub - GreenMail. The test doesn't send real emails, only verifies if the mail is prepared and sent correctly if a real SMTP server is available in the production.

In order to send emails from your local environment, you need to setup some SMTP server, but then, automated verification if the mail is actually sent is a completely different story.