第?17?章?使用Spring郵件抽象層發送Email

17.1.?簡介

Spring提供了一個發送電子郵件的高級抽象層，它向用戶屏蔽了底層郵件系統的一些細節，同時負責低層次的代表客戶端的資源處理。

17.2.?Spring郵件抽象結構

Spring郵件抽象層的主要包為org.springframework.mail。它包括了發送電子郵件的主要接口MailSender和 封裝了簡單郵件的屬性如from,?to,cc,?subject,?text的值對象叫做SimpleMailMessage。 一個以MailException為root的checked Exception繼承樹，它們提供了對底層郵件系統異常的高級別抽象。 請參考JavaDocs來得到關于郵件異常層次的更多的信息。

為了使用JavaMail中的一些特色如MIME類型的消息,Spring也提供了一個MailSender的子接口, 名為org.springframework.mail.javamail.JavaMailSender，同時也提供了一個對JavaMail的MIME類型的消息分塊的回調interface， 名為org.springframework.mail.javamail.MimeMessagePreparator

MailSender:

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;}

JavaMailSender:

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;}

MimeMessagePreparator:

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;}

17.3.?使用Spring郵件抽象

讓我們來假設有一個業務接口名為OrderManager

public interface OrderManager {void placeOrder(Order order); }

同時有一個use case為：需要生成帶有訂單號的email信息,并向客戶發送該訂單。 為了這個目的我們會使用MailSender和SimpleMailMessage。

請注意,通常情況下,我們在業務代碼中使用接口而讓Spring ioc容器負責組裝我們需要的合作者。

這里為OrderManager的一個實現

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 businness calculations....//... * Call the collaborators to persist the order//Create a threadsafe "sandbox" of the messageSimpleMailMessage 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 onSystem.err.println(ex.getMessage()); }} }

上面的代碼的bean的定義應該是這樣的:

<bean id="mailSender"class="org.springframework.mail.javamail.JavaMailSenderImpl"><property name="host"><value>mail.mycompany.com</value></property> </bean><bean id="mailMessage"class="org.springframework.mail.SimpleMailMessage"><property name="from"><value>customerservice@mycompany.com</value></property><property name="subject"><value>Your order</value></property> </bean><bean id="orderManager"class="com.mycompany.businessapp.support.OrderManagerImpl"><property name="mailSender"><ref bean="mailSender"/></property><property name="message"><ref bean="mailMessage"/></property> </bean>

下面是OrderManager的實現，使用了MimeMessagePreparator回調接口。 請注意這里的mailSender屬性類型為JavaMailSender,這樣做是為了能夠使用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 businness calculations....//... * Call the collaborators to persist the orderMimeMessagePreparator preparator = new MimeMessagePreparator() {public void prepare(MimeMessage mimeMessage) throws MessagingException {mimeMessage.setRecipient(Message.RecipientType.TO, new InternetAddress(order.getCustomer().getEmailAddress()));mimeMessage.setFrom(new InternetAddress("mail@mycompany.com"));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 onSystem.err.println(ex.getMessage()); }} }

如果你想使用JavaMail MimeMessage以獲得全部的能力，只需要你指尖輕觸鍵盤即可使用MimeMessagePreparator。

請注意這部分郵件代碼是一個橫切關注點，是一個可以重構至一個定制的SpringAOP advice的完美候選者, 這樣就可以不費力的應用到目標對象OrderManager上來。關于這一點請看AOP章節。

17.3.1.?可插拔的MailSender實現

Spring提供兩種MailSender的實現:標準的JavaMail實現和在http://servlets.com/cos?(com.oreilly.servlet)里的Jason Hunter's?MailMessage類之上的實現。請參考JavaDocs以得到進一步的信息。

from:?http://docs.huihoo.com/spring/zh-cn/mail.html

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