JavaMail API - 轉發郵件

在本章中，我們將瞭解如何使用 JavaMail API 轉發電子郵件。下面程式中遵循的基本步驟是

獲取包含 POP 和 SMPT 伺服器詳細資訊的 Session 物件。我們需要 POP 資訊來檢索郵件，需要 SMPT 資訊來發送郵件。
建立 POP3 store 物件並連線到儲存。
建立 Folder 物件並在您的郵箱中開啟相應的資料夾。
檢索郵件。
遍歷郵件，如果您想轉發，則輸入“Y”或“y”。
獲取郵件的所有資訊（收件人、發件人、主題、內容）。
透過處理構成郵件的各個部分來構建轉發郵件。第一部分將是郵件正文，第二部分將是需要轉發的郵件。將兩者合併成多部分。然後，您將多部分新增到正確定址的郵件中併發送。
分別關閉 Transport、folder 和 store 物件。

這裡我們使用了 JangoSMPT 伺服器，透過該伺服器將電子郵件傳送到我們的目標電子郵件地址。設定在環境設定章節中進行了說明。

建立 Java 類

建立一個名為 ForwardEmail 的 Java 類檔案，其內容如下所示

package com.tutorialspoint;

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();
   }
}

}

您可以透過取消註釋語句 session.setDebug(true); 來開啟除錯。

編譯和執行

現在我們的類已準備就緒，讓我們編譯上面的類。我已將類 ForwardEmail.java 儲存到目錄：/home/manisha/JavaMailAPIExercise。我們需要將 javax.mail.jar 和 activation.jar 這兩個 jar 包放在類路徑中。從命令提示符執行以下命令來編譯類（這兩個 jar 包都放置在 /home/manisha/ 目錄中）

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

現在類已編譯，執行以下命令執行

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

驗證輸出

您應該在命令控制檯上看到以下訊息

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....

檢查郵件傳送到的收件箱。在我們的例子中，轉發的郵件將如下所示

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