Spring提供了一个发送电子邮件的高级抽象层，它向用户屏蔽了底层邮件系统的一些细节，同时代表客户端负责底层的资源处理。

Spring邮件抽象层的主要包为org.springframework.mail。它包括了发送电子邮件的主要接口MailSender，和值对象SimpleMailMessage，它封装了简单邮件的属性如from, to,cc, subject,text。 包里还包含一棵以MailException为根的checked Exception继承树，它们提供了对底层邮件系统异常的高级别抽象。 要获得关于邮件异常层次的更丰富的信息，请参考Javadocs。

为了使用JavaMail中的一些特色, 比如MIME类型的信件, Spring提供了MailSender的一个子接口, 即org.springframework.mail.javamail.JavaMailSender。Spring还提供了一个回调接口org.springframework.mail.javamail.MimeMessagePreparator, 用于准备JavaMail的MIME信件。

public interface MailSender {

    /**
     * Send the given simple mail message.
     * @param simpleMessage message to send
     * @throws MailException in case of message, authentication, or send errors
     */
    public void send(SimpleMailMessage simpleMessage) throws MailException;

    /**
     * Send the given array of simple mail messages in batch.
     * @param simpleMessages messages to send
     * @throws MailException in case of message, authentication, or send errors
     */
    public void send(SimpleMailMessage[] simpleMessages) throws MailException;

}

public interface JavaMailSender extends MailSender {

    /**
     * Create a new JavaMail MimeMessage for the underlying JavaMail Session
     * of this sender. Needs to be called to create MimeMessage instances
     * that can be prepared by the client and passed to send(MimeMessage).
     * @return the new MimeMessage instance
     * @see #send(MimeMessage)
     * @see #send(MimeMessage[])
     */
    public MimeMessage createMimeMessage();

    /**
     * Send the given JavaMail MIME message.
     * The message needs to have been created with createMimeMessage.
     * @param mimeMessage message to send
     * @throws MailException in case of message, authentication, or send errors
     * @see #createMimeMessage
     */
    public void send(MimeMessage mimeMessage) throws MailException;

    /**
     * Send the given array of JavaMail MIME messages in batch.
     * The messages need to have been created with createMimeMessage.
     * @param mimeMessages messages to send
     * @throws MailException in case of message, authentication, or send errors
     * @see #createMimeMessage
     */
    public void send(MimeMessage[] mimeMessages) throws MailException;

    /**
     * Send the JavaMail MIME message prepared by the given MimeMessagePreparator.
     * Alternative way to prepare MimeMessage instances, instead of createMimeMessage
     * and send(MimeMessage) calls. Takes care of proper exception conversion.
     * @param mimeMessagePreparator the preparator to use
     * @throws MailException in case of message, authentication, or send errors
     */
    public void send(MimeMessagePreparator mimeMessagePreparator) throws MailException;

    /**
     * Send the JavaMail MIME messages prepared by the given MimeMessagePreparators.
     * Alternative way to prepare MimeMessage instances, instead of createMimeMessage
     * and send(MimeMessage[]) calls. Takes care of proper exception conversion.
     * @param mimeMessagePreparators the preparator to use
     * @throws MailException in case of message, authentication, or send errors
     */
    public void send(MimeMessagePreparator[] mimeMessagePreparators) throws MailException;

}

public interface MimeMessagePreparator {

    /**
     * Prepare the given new MimeMessage instance.
     * @param mimeMessage the message to prepare
     * @throws MessagingException passing any exceptions thrown by MimeMessage
     * methods through for automatic conversion to the MailException hierarchy
     */
    void prepare(MimeMessage mimeMessage) throws MessagingException;

}

假设某个业务接口名为 OrderManager:

public interface OrderManager {

    void placeOrder(Order order);
}

同时有一个用例为：需要生成带有订单号的email信件, 并向客户发送该订单。 为此，我们会使用MailSender接口和SimpleMailMessage类。

请注意,通常情况下,我们在业务代码中使用接口而让Spring ioc容器负责组装我们需要的合作者。

以下是OrderManager的实现:

import org.springframework.mail.MailException;
import org.springframework.mail.MailSender;
import org.springframework.mail.SimpleMailMessage;

public class OrderManagerImpl implements OrderManager {

    private MailSender mailSender;
    private SimpleMailMessage message;

    public void setMailSender(MailSender mailSender) {
        this.mailSender = mailSender;
    }

    public void setMessage(SimpleMailMessage message) {
        this.message = message;
    }

    public void placeOrder(Order order) {

        // Do the business calculations...
        // Call the collaborators to persist the order...

        //Create a thread safe "sandbox" of the message
        SimpleMailMessage msg = new SimpleMailMessage(this.message);
        msg.setTo(order.getCustomer().getEmailAddress());
        msg.setText(
            "Dear "
                + order.getCustomer().getFirstName()
                + order.getCustomer().getLastName()
                + ", thank you for placing order. Your order number is "
                + order.getOrderNumber());
        try{
            mailSender.send(msg);
        }
        catch(MailException ex) {
            //log it and go on
            System.err.println(ex.getMessage());            
        }
    }
}

上面的代码的bean定义应该是这样的:

<bean id="mailSender" class="org.springframework.mail.javamail.JavaMailSenderImpl">
  <property name="host" value="mail.mycompany.com"/>
</bean>

<bean id="mailMessage" class="org.springframework.mail.SimpleMailMessage">
  <property name="from" value="[email protected]"/>
  <property name="subject" value="Your order"/>
</bean>

<bean id="orderManager" class="com.mycompany.businessapp.support.OrderManagerImpl">
  <property name="mailSender" ref="mailSender"/>
  <property name="message" ref="mailMessage"/>
</bean>

下面是OrderManager接口的实现，使用了MimeMessagePreparator回调接口。 请注意这里的mailSender属性的类型为JavaMailSender,这样做是为了能够使用JavaMail的MimeMessage：

import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

import javax.mail.internet.MimeMessage;
import org.springframework.mail.MailException;
import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.mail.javamail.MimeMessagePreparator;

public class OrderManagerImpl implements OrderManager {

    private JavaMailSender mailSender;
    
    public void setMailSender(JavaMailSender mailSender) {
        this.mailSender = mailSender;
    }

    public void placeOrder(final Order order) {

        // Do the business calculations...
        // Call the collaborators to persist the order...
        
        MimeMessagePreparator preparator = new MimeMessagePreparator() {
        
            public void prepare(MimeMessage mimeMessage) throws MessagingException {
        
                mimeMessage.setRecipient(Message.RecipientType.TO, 
                        new InternetAddress(order.getCustomer().getEmailAddress()));
                mimeMessage.setFrom(new InternetAddress("[email protected]"));
                mimeMessage.setText(
                    "Dear "
                        + order.getCustomer().getFirstName()
                        + order.getCustomer().getLastName()
                        + ", thank you for placing order. Your order number is "
                        + order.getOrderNumber());
            }
        };
        try {
            mailSender.send(preparator);
        }
        catch (MailException ex) {
            //log it and go on
            System.err.println(ex.getMessage());            
        }
    }
}

如果你想获得JavaMail MimeMessage的全部能力，你可以使用MimeMessagePreparator。

	Note
	以上的邮件代码是一个横切关注点，是重构为定制SpringAOP advice的完美候选者,这样就可以在目标对象OrderManager合适的joinpoint中运行。请参阅Chapter 6, 使用Spring进行面向切面编程（AOP）章节。

org.springframework.mail.javamail.MimeMessageHelper是处理JavaMail邮件常用的顺手组件之一。它可以让你摆脱繁复的javax.mail.internetAPI类。下面是一些通常的场景：

// of course you would use DI in any real-world cases
JavaMailSenderImpl sender = new JavaMailSenderImpl();
sender.setHost("mail.host.com");

MimeMessage message = sender.createMimeMessage();
MimeMessageHelper helper = new MimeMessageHelper(message);
helper.setTo("[email protected]");
helper.setText("Thank you for ordering!");

sender.send(message);

22.4.2. 发送附件和嵌入式资源(inline resources)

Email允许添加附件，也允许在multipart信件中内嵌资源。内嵌资源可能是你在信件中希望使用的图像，或者样式表，但是又不想把它们作为附件。下面的例子演示如何使用MimeMessageHelper来发送带有内嵌图像的email。

JavaMailSenderImpl sender = new JavaMailSenderImpl();
sender.setHost("mail.host.com");

MimeMessage message = sender.createMimeMessage();

// use the true flag to indicate you need a multipart message
MimeMessageHelper helper = new MimeMessageHelper(message, true);
helper.setTo("[email protected]");

// use the true flag to indicate the text included is HTML
helper.setText("<html><body><img src='cid:identifier1234'></body></html>", true);

// let's include the infamous windows Sample file (this time copied to c:/)
FileSystemResource res = new FileSystemResource(new File("c:/Sample.jpg"));
helper.addInline("identifier1234", res);

// if you would need to include the file as an attachment, use
// the various addAttachment() methods on the MimeMessageHelper

sender.send(message);

	Warning
	如你所见，嵌入式资源使用Content-ID(上例中是identifier1234)来插入到mime信件中去。你加入文本或者资源的顺序是非常重要的。首先，你加入文本，随后是资源。如果你弄反了顺序，它将无法正常运作！