RFC822电子邮件-格式化程序-Android / iOS-创建MimeMessage，无需会话或主机

Question

我有以下电子邮件：

Subject = Hello!
Body = Bla bla bla bla.
Recipients = "carlos@mail.com", "mike@mail.com"

现在，我想解析遵循RFC822的字段，但是找不到。

我需要的？

所有字段（主题，正文，收件人）->格式化程序（java和/或Objective-c）->根据RC822的字符串

我尝试了什么？

• https://code.google.com/archive/p/javamail-android/
• mime4j

问题是它们是面向会话的，我没有凭据或主机。

更新

我需要像这样 ，而是使用message.writeTo(...)我想是这样String dataRFC822 = message.getRFC822String();

// Recipient's email ID needs to be mentioned.
      String to = "destinationemail@gmail.com";

      // Sender's email ID needs to be mentioned
      String from = "fromemail@gmail.com";

      // Get the Session object. Which I have not and I don't want it.
      Session session = Session.getInstance(props,
         new javax.mail.Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
               return new PasswordAuthentication(username, password);
            }
         });

      try {
         // Create a default MimeMessage object.
         Message message = new MimeMessage(session);

         // Set From: header field of the header.
         message.setFrom(new InternetAddress(from));

         // Set To: header field of the header.
         message.setRecipients(Message.RecipientType.TO,
            InternetAddress.parse(to));

         // Set Subject: header field
         message.setSubject("Testing Subject");

         // Create the message part
         BodyPart messageBodyPart = new MimeBodyPart();

         // Now set the actual message
         messageBodyPart.setText("This is message body");

         // Create a multipar message
         Multipart multipart = new MimeMultipart();

         // Set text message part
         multipart.addBodyPart(messageBodyPart);

         // Part two is attachment
         messageBodyPart = new MimeBodyPart();
         String filename = "/home/manisha/file.txt";
         DataSource source = new FileDataSource(filename);
         messageBodyPart.setDataHandler(new DataHandler(source));
         messageBodyPart.setFileName(filename);
         multipart.addBodyPart(messageBodyPart);

         // Send the complete message parts
         message.setContent(multipart);

         //instead write it on a stream i I want get back the string formated according to rfc822
         message.writeTo(...);


      } catch (MessagingException e) {
         throw new RuntimeException(e);
      }

Answer 1

您可以手动创建与RFC822兼容的字符串，如果您不附加文件或绝对需要多部分的mime消息，则这种方法更简单：

String makeRfc822email(String from, String to, String subject, String message) {
  StringBuilder builder = new StringBuilder();
  builder.append("From: ");
  builder.append(from);
  builder.append("\n");

  builder.append("To: ");
  builder.append(to);
  builder.append("\n");

  builder.append("Subject: ");
  builder.append(subject);
  builder.append("\n\n");  // Blank line before message.

  builder.append(message);

  return builder.toString();
}

Answer 2

正如@Shadowfacts指出的那样，您可以使用ByteArrayOutputStream。

诀窍是只要您不真正使用会话对象来连接到服务器，就不需要会话对象上的凭据。 然后，我重新使用了大部分代码：

String to = "destinationemail@gmail.com";
String from = "fromemail@gmail.com";

// Empty properties and null credentials makes a valid session.
Properties props = new Properties();
Session session = Session.getInstance(props, null);

Message message = new MimeMessage(session);
message.setFrom(new InternetAddress(from));
message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(to));
message.setSubject("Testing Subject");
BodyPart messageBodyPart = new MimeBodyPart();
messageBodyPart.setText("This is message body");

Multipart multipart = new MimeMultipart();
multipart.addBodyPart(messageBodyPart);

messageBodyPart = new MimeBodyPart();
String filename = "/etc/hostname";
DataSource source = new FileDataSource(filename);
messageBodyPart.setDataHandler(new DataHandler(source));
messageBodyPart.setFileName(filename);
multipart.addBodyPart(messageBodyPart);

message.setContent(multipart);

ByteArrayOutputStream baos = new ByteArrayOutputStream();
message.writeTo(baos);
String rfc822message = baos.toString();
System.out.print(rfc822message);

我得到的结果是：

From: fromemail@gmail.com
To: destinationemail@gmail.com
Message-ID: <392292416.1.1481815905219@nitoshpas>
Subject: Testing Subject
MIME-Version: 1.0
Content-Type: multipart/mixed; 
boundary="----=_Part_0_59559151.1481815905197"

------=_Part_0_59559151.1481815905197
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit

This is message body
------=_Part_0_59559151.1481815905197
Content-Type: application/octet-stream; name="/etc/hostname"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="/etc/hostname"

nitoshpas

------=_Part_0_59559151.1481815905197--

Answer 3

您可以使用ByteArrayOutputStream ，它是OutputStream的实现，它写入byte数组。 您可以创建此方法的一个实例，并将其传递给方法上的writeTo(OutputStream) ，然后从那里调用ByteArrayOutputStream上的toString以检索消息的String表示形式。

ByteArrayOutputStream out = new ByteArrayOutputStream();
message.writeto(out);
String s = out.toString();