转发电子邮件（Forwarding Emails）

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小牛编辑

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2023-12-01

在本章中，我们将了解如何使用JavaMail API转发电子邮件。以下程序中遵循的基本步骤是:

在属性中获取具有POP和SMPT服务器详细信息的Session对象。我们需要POP详细信息来检索消息和SMPT详细信息以发送消息。
创建POP3商店对象并连接到商店。
创建文件夹对象并在邮箱中打开相应的文件夹。
检索邮件。
如果要转发，请浏览消息并输入“Y”或“y”。
获取邮件的所有信息（收件人，发件人，主题，内容）。
通过使用组成消息的部分来构建转发消息。第一部分是消息的文本，第二部分是要转发的消息。将两者组合成一个多部分。然后将多部分添加到正确寻址的消息并发送它。
分别关闭Transport，文件夹和存储对象。

在这里，我们使用了JangoSMPT服务器，通过该服务器将电子邮件发送到我们的目标电子邮件地址。环境设置章节中介绍了该设置。

创建Java类 (Create Java Class)

创建一个java类文件ForwardEmail ，其内容如下:

package cn.xnip;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Date;
import java.util.Properties;
import javax.mail.BodyPart;
import javax.mail.Folder;
import javax.mail.Message;
import javax.mail.Multipart;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Store;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;
public class ForwardEmail {
   public static void main(String[] args) {
      Properties properties = new Properties();
      properties.put("mail.store.protocol", "pop3");
      properties.put("mail.pop3s.host", "pop.gmail.com");
      properties.put("mail.pop3s.port", "995");
      properties.put("mail.pop3.starttls.enable", "true");
      properties.put("mail.smtp.auth", "true");
      properties.put("mail.smtp.host", "relay.jangosmtp.net");
      properties.put("mail.smtp.port", "25");
      Session session = Session.getDefaultInstance(properties);
      try {
         // session.setDebug(true);
         // Get a Store object and connect to the current host
         Store store = session.getStore("pop3s");
         store.connect("pop.gmail.com", "xyz@gmail.com",
            "*****");//change the user and password accordingly
         // Create a Folder object and open the folder
         Folder folder = store.getFolder("inbox");
         folder.open(Folder.READ_ONLY);
         BufferedReader reader = new BufferedReader(new InputStreamReader(
            System.in));
         Message[] messages = folder.getMessages();
         if (messages.length != 0) {
         for (int i = 0, n = messages.length; i < n; i++) {
            Message message = messages[i];
            // Get all the information from the message
            String from = InternetAddress.toString(message.getFrom());
            if (from != null) {
               System.out.println("From: " + from);
            }
            String replyTo = InternetAddress.toString(message
               .getReplyTo());
            if (replyTo != null) {
               System.out.println("Reply-to: " + replyTo);
            }
            String to = InternetAddress.toString(message
               .getRecipients(Message.RecipientType.TO));
            if (to != null) {
               System.out.println("To: " + to);
            }
            String subject = message.getSubject();
            if (subject != null) {
               System.out.println("Subject: " + subject);
            }
            Date sent = message.getSentDate();
            if (sent != null) {
               System.out.println("Sent: " + sent);
            }
            System.out.print("Do you want to reply [y/n] : ");
            String ans = reader.readLine();
            if ("Y".equals(ans) || "y".equals(ans)) {
               Message forward = new MimeMessage(session);
               // Fill in header
               forward.setRecipients(Message.RecipientType.TO,
               InternetAddress.parse(from));
               forward.setSubject("Fwd: " + message.getSubject());
               forward.setFrom(new InternetAddress(to));
               // Create the message part
               MimeBodyPart messageBodyPart = new MimeBodyPart();
               // Create a multipart message
               Multipart multipart = new MimeMultipart();
               // set content
               messageBodyPart.setContent(message, "message/rfc822");
               // Add part to multi part
               multipart.addBodyPart(messageBodyPart);
               // Associate multi-part with message
               forward.setContent(multipart);
               forward.saveChanges();
               // Send the message by authenticating the SMTP server
               // Create a Transport instance and call the sendMessage
               Transport t = session.getTransport("smtp");
               try {
                  //connect to the smpt server using transport instance
		  //change the user and password accordingly
                  t.connect("abc", "*****");
                  t.sendMessage(forward, forward.getAllRecipients());
               } finally {
                  t.close();
               }
               System.out.println("message forwarded successfully....");
            // close the store and folder objects
            folder.close(false);
            store.close();
            }// end if
         }// end for
   }// end if
   } catch (Exception e) {
      e.printStackTrace();
   }
}
}

您可以通过取消注释语句session.setDebug(true);来设置调试session.setDebug(true);

编译和运行 (Compile and Run)

现在我们的课已经准备好了，让我们编译上面的类。我已将类ForwardEmail.java保存到目录: /home/manisha/JavaMailAPIExercise 。我们需要在类路径中使用jars javax.mail.jar和activation.jar 。执行以下命令从命令提示符编译类（两个jar放在/ home/manisha /目录中）:

javac -cp /home/manisha/activation.jar:/home/manisha/javax.mail.jar: ForwardEmail.java

现在编译了类，执行以下命令来运行:

java -cp /home/manisha/activation.jar:/home/manisha/javax.mail.jar: ForwardEmail

验证输出 (Verify Output)

您应该在命令控制台上看到以下消息:

From: ABC <abc@gmail.com>
Reply-to: abc@trioteksolutions.com
To: XYZ <xyz@gmail.com>
Subject: Hi today is a nice day
Sent: Thu Oct 17 15:58:37 IST 2013
Do you want to reply [y/n] : y
message forwarded successfully....

检查邮件发送到的收件箱。在我们的例子中，转发的消息如下所示: