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1. Overview

In this tutorial, we'll walk through the steps needed to send emails from both a plain vanilla Spring application as well as a Spring Boot application. For the former, we'll use the JavaMail library, and the latter will use the spring-boot-starter-mail dependency.

Further reading:

Registration – Activate a New Account by Email

Verify newly registered users by sending them a verification token via email before allowing them to log in - using Spring Security.

Spring Boot Actuator

A quick intro to Spring Boot Actuators - using and extending the existing ones, configuration and rolling your own.

2. Maven Dependencies

First, we need to add the dependencies to our pom.xml.

2.1. Spring

Here is what we'll add for use in the plain vanilla Spring framework:

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context-support</artifactId>
    <version>5.2.8.RELEASE</version>
</dependency>

The latest version can be found here.

2.2. Spring Boot

And for Spring Boot:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-mail</artifactId>
    <version>2.3.4.RELEASE</version>
</dependency>

The latest version is available in the Maven Central repository.

3. Mail Server Properties

The interfaces and classes for Java mail support in the Spring framework are organized as follows:

  1. MailSender interface: the top-level interface that provides basic functionality for sending simple emails
  2. JavaMailSender interface: the subinterface of the above MailSender. It supports MIME messages and is mostly used in conjunction with the MimeMessageHelper class for the creation of a MimeMessage. It's recommended to use the MimeMessagePreparator mechanism with this interface.
  3. JavaMailSenderImpl class provides an implementation of the JavaMailSender interface. It supports the MimeMessage and SimpleMailMessage.
  4. SimpleMailMessage class: used to create a simple mail message including the from, to, cc, subject and text fields
  5. MimeMessagePreparator interface provides a callback interface for the preparation of MIME messages.
  6. MimeMessageHelper class: helper class for the creation of MIME messages. It offers support for images, typical mail attachments and text content in an HTML layout.

In the following sections, we show how to use these interfaces and classes.

3.1. Spring Mail Server Properties

Mail properties that are needed to specify, for example, the SMTP server may be defined using the JavaMailSenderImpl.

For Gmail, this can be configured as shown below:

@Bean
public JavaMailSender getJavaMailSender() {
    JavaMailSenderImpl mailSender = new JavaMailSenderImpl();
    mailSender.setHost("smtp.gmail.com");
    mailSender.setPort(587);
    
    mailSender.setUsername("[email protected]");
    mailSender.setPassword("password");
    
    Properties props = mailSender.getJavaMailProperties();
    props.put("mail.transport.protocol", "smtp");
    props.put("mail.smtp.auth", "true");
    props.put("mail.smtp.starttls.enable", "true");
    props.put("mail.debug", "true");
    
    return mailSender;
}

3.2. Spring Boot Mail Server Properties

Once the dependency is in place, the next step is to specify the mail server properties in the application.properties file using the spring.mail.* namespace.

We can specify the properties for the Gmail SMTP server this way:

spring.mail.host=smtp.gmail.com
spring.mail.port=587
spring.mail.username=<login user to smtp server>
spring.mail.password=<login password to smtp server>
spring.mail.properties.mail.smtp.auth=true
spring.mail.properties.mail.smtp.starttls.enable=true

Some SMTP servers require a TLS connection, so we use the property spring.mail.properties.mail.smtp.starttls.enable to enable a TLS-protected connection.

3.2.1. Gmail SMTP Properties

We can send an email via Gmail SMTP server. Have a look at the documentation to see the Gmail outgoing mail SMTP server properties.

Our application.properties file is already configured to use Gmail SMTP (see the previous section).

Note that the password for our account should not be an ordinary password but an application password generated for our Google account. Follow this link to see the details and to generate your Google App Password.

3.2.2. SES SMTP Properties

To send emails using Amazon SES, we set our application.properties:

spring.mail.host=email-smtp.us-west-2.amazonaws.com
spring.mail.username=username
spring.mail.password=password
spring.mail.properties.mail.transport.protocol=smtp
spring.mail.properties.mail.smtp.port=25
spring.mail.properties.mail.smtp.auth=true
spring.mail.properties.mail.smtp.starttls.enable=true
spring.mail.properties.mail.smtp.starttls.required=true

Please be aware that Amazon requires us to verify our credentials before using them. Follow the link to verify your username and password.

4. Sending Email

Once dependency management and configuration are in place, we can use the aforementioned JavaMailSender to send an email.

Since both the plain vanilla Spring framework as well as the Boot version of it handle the composing and sending of emails in a similar way, we won't have to distinguish between the two in the subsections below.

4.1. Sending Simple Emails

Let's first compose and send a simple email message without any attachments:

@Component
public class EmailServiceImpl implements EmailService {

    @Autowired
    private JavaMailSender emailSender;

    public void sendSimpleMessage(
      String to, String subject, String text) {
        ...
        SimpleMailMessage message = new SimpleMailMessage(); 
        message.setFrom("[email protected]");
        message.setTo(to); 
        message.setSubject(subject); 
        message.setText(text);
        emailSender.send(message);
        ...
    }
}

Note that even though it's not mandatory to provide the from address, many SMTP servers would reject such messages. That's why we use the [email protected] email address in our EmailService implementation.

4.2. Sending Emails With Attachments

Sometimes Spring's simple messaging is not enough for our use cases.

For example, we want to send an order confirmation email with an invoice attached. In this case, we should use a MIME multipart message from JavaMail library instead of SimpleMailMessage. Spring supports JavaMail messaging with the org.springframework.mail.javamail.MimeMessageHelper class.

First of all, we'll add a method to the EmailServiceImpl to send emails with attachments:

@Override
public void sendMessageWithAttachment(
  String to, String subject, String text, String pathToAttachment) {
    // ...
    
    MimeMessage message = emailSender.createMimeMessage();
     
    MimeMessageHelper helper = new MimeMessageHelper(message, true);
    
    helper.setFrom("[email protected]");
    helper.setTo(to);
    helper.setSubject(subject);
    helper.setText(text);
        
    FileSystemResource file 
      = new FileSystemResource(new File(pathToAttachment));
    helper.addAttachment("Invoice", file);

    emailSender.send(message);
    // ...
}

4.3. Simple Email Template

SimpleMailMessage class supports text formatting.

We can create a template for emails by defining a template bean in our configuration:

@Bean
public SimpleMailMessage templateSimpleMessage() {
    SimpleMailMessage message = new SimpleMailMessage();
    message.setText(
      "This is the test email template for your email:\n%s\n");
    return message;
}

Now we can use this bean as a template for email and only need to provide the necessary parameters to the template:

@Autowired
public SimpleMailMessage template;
...
String text = String.format(template.getText(), templateArgs);  
sendSimpleMessage(to, subject, text);

5. Handling Send Errors

JavaMail provides SendFailedException to handle situations when a message cannot be sent. But it is possible that we won't get this exception while sending an email to the incorrect address. The reason is the following:

The protocol specs for SMTP in RFC 821 specifies the 550 return code that the SMTP server should return when attempting to send an email to the incorrect address. But most of the public SMTP servers don't do this. Instead, they send a “delivery failed” email or give no feedback at all.

For example, Gmail SMTP server sends a “delivery failed” message. And we get no exceptions in our program.

So, we have a few options to handle this case:

  1. Catch the SendFailedException, which can never be thrown.
  2. Check our sender mailbox for the “delivery failed” message for some period of time. This is not straightforward, and the time period is not determined.
  3. If our mail server gives no feedback at all, we can do nothing.

6. Conclusion

In this quick article, we showed how to set up and send emails from a Spring Boot application.

The implementation of all these examples and code snippets can be found over on GitHub.

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