使用Spring发送E-mail

1.通常情况下使用JavaMail原始API进行邮件发送的代码示例

String host = "your.mail.host";

String username = "...";

String password = "...";

String protocal = "smtp";

String mailSubject = "邮件标题";

String mailContext = "邮件内容";

String mailEncoding = "UTF-8";

boolean plainTextMail = false;  //是否发送普通文本文件

Properties props = new Properties();

props.put("mail.smtp.auth","true");

Transport transport = null;

try{

     Session session = Session.getDefaultInstance(props,null);

     MimeMessage message = new MimeMessage(session);

     message.setRecipients(RecipientType.TO,new Address[]{new InternetAddress([e-mail])});

     message.setRecipient(RecipientType.CC,new InternetAddress([e-mail]));

     message.setFrom(new InternetAddress([e-mail]));

     message.setSubject(mailSubject,mailEncoding);

     if(plainTextMail){

           message.setText(mailContext,mailEncoding);

     }else{

           Multipart multipart= new MimeMultipart();

           BodyPart bodyPart = new MimeBodyPart();

           bodyPart.setText(mailContext);

           multiPart.addBodyPart(bodyPart);

           bodyPart = new MimeBodyPart();

           FileDataSource fds = new FileDataSource("attachment.name"); //添加附件

           bodyPart.setDataHandler(new DataHandler(fds));

           bodyPart.setFileName(fds.getName());

           multiPart.addBodyPart(bodyPart);

           message.setContent(multiPart);

     }

     transport = session.getTransport(protocal);

     transport.connect(host,username,password);

     transport.sendMessage(message,message.getAllRecipients());

}catch(Exception e){

     //根据情况处理异常

}finally{

     if(transport != null){

          try{

                 transport.close();

          }catch(MessagingException e){

                 e.printStackTrace();

          }

     }

}

使用JavaMail API发送邮件，我们需要设置JavaMail的Session需要的某些属性，然后根据Session构建相应的MimeMessage实例，并在构建完的MimeMessage实例上设置将要发送的消息的方方面面。在消息准备完成后，我们才通过Transport连接到邮件服务器，并发送准备好的邮件信息，还不要忘了异常的处理和Transport的关闭

 

2.Spring的E-mail抽象层分析

Spring所提供的E-mail抽象层主要体现在两个层次，即MailMessage抽象层次和MailSender抽象层次

<<Interface>>       

MailMessage--------SimpleMailMessage,MimeMailMessage

<<Interface>>

MailSender---------CosMailSenderImpl,<<Interface>>JavaMailSender---------JavaMailSenderImpl

MailMessage抽象层次在于对要发送的邮件信息进行抽象和建模，MailMessage作为该层次的统领，定义了一套标准的邮件信息操作方式

MailMessage主要有两个实现类，SimpleMailMessage代表了普通的文本邮件(plain text mail)，而MimeMailMessage则代表能够发送更丰富内容的MIME(Multipart Internet Message Encoding)类型的信息

mailMessage.setTo(...);

mailMessage.setCc(...);

mailMessage.setBcc(...);

...

MailSender抽象接口的主要目的即使屏蔽调各种E-mail解决方案的差异性，不管底层的E-mail解决方案如何变换，只需要把使用这些E-mail解决方案实现的MailSender实现类注入给依赖MailSender接口的对象即可

public interface MailSender{

      void send(SimpleMailMessage simpleMessage) throws MailException;

      void send(SimpleMailMessage[] simpleMessages) throws MailException;

}

JavaMailSender扩展自MailSender，在MailSender发送普通文本文件的基础上，添加了发送MIME邮件的功能。JavaMailSenderImpl封装JavaMail API使用的方法是模板方法模式

JavaMailSenderImpl实现类相关模板方法代码摘录

public void doSend(MimeMessage[] message2Send){

      //预处理

      Transport transport = getTransport(getSession());

      transport.connect(getHost(),getPort(),getUsername(),getPassword());

      try{

            for(int i = 0; i < mimeMessages.length; i++){

                  MimeMessage mimeMessage = mimeMessages[i];

                  transport.sendMessage(mimeMessage,mimeMessage.getAllRecipients());

            }

      }finally{

            transport.close();

      }

}

 

3.JavaMailSender提供了两种常用的邮件发送方式，一种是直接外部创建要发送的MailMessage实例，然后传给JavaMailSender发送；另一个则是使用JavaMailSender公开给我们的MimeMessagePreparator回调接口

1）直接创建邮件消息并发送

JavaMailSender mailSender = new JavaMailSenerImpl();

JavaMialSenderImpl javaMailSender = (JavaMailSenderImpl)mailSender;

javaMailSender.setHost("...");

javaMailSender.setUseranme("...");

javaMailSender.setPassword("...");

Properties javaMailProps = new Properties();

javaMailProps.put("mail.smtp.auth","true");

javaMailSender.setJavaMailProperties(javaMailProps);

//mailSender现在可以使用

JavaMailSenderImpl配置代码示例

<bean id="javaMailSender" class="org.springframework.mail.javamail.JavaMailSenderImpl">

      <property name="host" value="...">

      <property name="username" value="...">

      <property name="password" value="...">

      <property name="javaMailProperties">

             <props>

                     <prop key="mail.smtp.auth">true</prop>

             </props>

      </property>

</bean>

因为JavaMail的MimeMessage不能独立于Session而创建，所以只有在有了可用的JavaMailSender之后，才能开始创建要发送的邮件信息，要通过JavaMailSender的createMimeMessage()方法达成

MimeMessage javaMailMessage = mailSender.createMimeMessage();

MimeMailMessage messageWrapper = new MimeMailMessage(javaMailMessage);

messageWrapper.setTo("...");

messageWrapper.setFrom("...");

messageWrapper.setSubject("...");

messageWrapper.setText("...");

//其他设定...

mailSender.send(messageWrapper.getMimeMessage());

Spring提供的MimeMailMessage对createMimeMessage()返回的MimeMessage做了简单的包装

 

4.使用MimeMessagePreparator发送邮件

JavaMailSender还提供了使用MimeMessagePreparator回调接口的邮件发送方法。MimeMessagePreparator作为回调接口，可以获得JavaMailSender公开给它的MimeMessage实例

沿用已经设定完毕的JavaMailSender实例

mailSender.send(new MimeMessagePreparator(){

           public void prepare(MimeMessage message) throws Exception{

                    MimeMailMessage messageWrapper = new MimeMailMessage(message);

                    messageWrapper.setTo("...");

                    messageWrapper.setFrom("...");

                    messageWrapper.setSubject("...");

                    messageWrapper.setText("...");

           }

} );

MimeMessageHelper可以帮助我们完成更加丰富的邮件内容设定

MimeMessageHelper使用代码示例

mailSender.send(new MimeMessagePreparator(){

      public void prepare(MimeMessage message) throws Exception{

            MimeMessageHelper messageHelper = new MimeMessageHelper(message,true,"UTF-8");

            messageHelper.setFrom("...");

            messageHelper.setTo("...");

            messageHelper.setSubject("...");

            StringBuilder builder = new StringBuilder("");

            builder.append("<html><head><meta http-equiv='ContentType' content='text/html;charset=utf-8'></head><body><pre>");

            builder.append("<img src='cid:inlinePic'>"); 

            builder.append("</pre></body></html>");

            messageHelper.setText(builder.toString(),true);

            messageHelper.addInline("inlinePic",new ClassPathResource("img/picture.gif"));

            messageHelper.addAttachment("fileName.pdf",new ClassPathResource("yourFile.pdf"));           

      }

});

JavaMailSender结合MimeMessagePreparator和MimeMessageHelper的组合，是使用JavaMailSender发送邮件的最常用方式