通过 apache common java api 转发带有附件的电子邮件（使用 JavaMailApi 读取）

Question

我正在阅读来自 Outlook 网络邮件的邮件并获取邮件列表（'javax.mail.Message'）。 现在我想使用 java 程序将这些消息转发到另一个 email 地址。

    private void sendTestMail(String from, String subject, String sentDate, Object object, Message message)
            throws EmailException, Exception {

        MultiPartEmail email = new MultiPartEmail();
        email.setHostName(forwardHost);

        email.addTo(mailRecipients(to));
        email.setFrom(emailFrom);
        email.setSubject(subject);
        email.setMsg("Testing email by sahil.");

        EmailAttachment attachment = new EmailAttachment();
        attachment.setPath("c:\\sahil\\test.jpg");
        attachment.setDisposition(EmailAttachment.ATTACHMENT);
        attachment.setDescription("Picture_of_John");
        attachment.setName("John.jpg");
        email.attach(attachment);  


        MimeMultipart multiPart = getMimeMultipart(message);
        email.addPart(multiPart);

        email.send();
    }   

如果我在上面的代码中的两行下面评论，那么它工作正常。

MimeMultipart multiPart = getMimeMultipart(message);
email.addPart(multiPart);

但是有了这两行，我得到了例外。

2020-04-20 15:41:44,271 ERROR com.st.ict.ols.service.impl.ReplyToMessageServiceImpl [main]  Inner Exception occurred while processing individual message. Error stacktrace is[org.apache.commons.mail.EmailException: Sending the email to the following server failed : smtpapp1.sgp.st.com:25
    at org.apache.commons.mail.Email.sendMimeMessage(Email.java:1421)
    at org.apache.commons.mail.Email.send(Email.java:1448)
    at com.st.ict.ols.service.impl.ReplyToMessageServiceImpl.sendTestMail(ReplyToMessageServiceImpl.java:342)
    at com.st.ict.ols.service.impl.ReplyToMessageServiceImpl.processMessage(ReplyToMessageServiceImpl.java:167)
    at com.st.ict.ols.service.impl.MessageServiceImpl.processMessage(MessageServiceImpl.java:22)
    at com.st.ict.ols.OlsMailSenderApplication.run(OlsMailSenderApplication.java:36)
    at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:732)
    at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:716)
    at org.springframework.boot.SpringApplication.afterRefresh(SpringApplication.java:703)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:304)
    at com.st.ict.ols.OlsMailSenderApplication.main(OlsMailSenderApplication.java:27)
Caused by: javax.mail.MessagingException: IOException while sending message;
  nested exception is:
    java.io.IOException: Exception writing Multipart
    at com.sun.mail.smtp.SMTPTransport.sendMessage(SMTPTransport.java:1308)
    at javax.mail.Transport.send0(Transport.java:255)
    at javax.mail.Transport.send(Transport.java:124)
    at org.apache.commons.mail.Email.sendMimeMessage(Email.java:1411)
    ... 10 more
Caused by: java.io.IOException: Exception writing Multipart
    at com.sun.mail.handlers.multipart_mixed.writeTo(multipart_mixed.java:83)
    at javax.activation.ObjectDataContentHandler.writeTo(DataHandler.java:884)
    at javax.activation.DataHandler.writeTo(DataHandler.java:317)
    at javax.mail.internet.MimeBodyPart.writeTo(MimeBodyPart.java:1652)
    at javax.mail.internet.MimeBodyPart.writeTo(MimeBodyPart.java:961)
    at javax.mail.internet.MimeMultipart.writeTo(MimeMultipart.java:553)
    at com.sun.mail.handlers.multipart_mixed.writeTo(multipart_mixed.java:81)
    at javax.activation.ObjectDataContentHandler.writeTo(DataHandler.java:884)
    at javax.activation.DataHandler.writeTo(DataHandler.java:317)
    at javax.mail.internet.MimeBodyPart.writeTo(MimeBodyPart.java:1652)
    at javax.mail.internet.MimeMessage.writeTo(MimeMessage.java:1850)
    at com.sun.mail.smtp.SMTPTransport.sendMessage(SMTPTransport.java:1259)
    ... 13 more
Caused by: javax.mail.MessagingException: Empty multipart: multipart/mixed; 
    boundary="----=_Part_1_1176580790.1587377502798"
    at javax.mail.internet.MimeMultipart.writeTo(MimeMultipart.java:548)
    at com.sun.mail.handlers.multipart_mixed.writeTo(multipart_mixed.java:81)
    ... 24 more

Code I've written to retrieve MimeMultipart from JavaMailApi's Message object to set in apache common's org.apache.commons.mail.MultiPartEmail Object using attach function.

    public MimeMultipart getMimeMultipart(Message message) throws Exception {
        Object content = message.getContent();
        if (content instanceof String)
            return null;        

        if (content instanceof MimeMultipart) {
            MimeMultipart multiPartResult = new MimeMultipart();
            MimeMultipart multiPart = (MimeMultipart) content;

            List<BodyPart> result = new ArrayList<>();
            for (int i = 0; i < multiPart.getCount(); i++) {
                BodyPart bodyPart = (BodyPart) multiPart.getBodyPart(i);
                result.addAll(getMimeMultipart(bodyPart));
            }
            for(BodyPart part:result) {
                multiPart.addBodyPart(part);
            }
            return multiPartResult;

        }
        return null;
    }

    private List<BodyPart> getMimeMultipart(BodyPart part) throws Exception{
        List<BodyPart> result = new ArrayList<>();
        Object content = part.getContent();

        if (content instanceof InputStream || content instanceof String) {
            if (Part.ATTACHMENT.equalsIgnoreCase(part.getDisposition()) || StringUtils.isNotBlank(part.getFileName())) {
                result.add(part);
            }
            return result;
        }

        if (content instanceof MimeMultipart) {
                MimeMultipart multipart = (MimeMultipart) content;
                for (int i = 0; i < multipart.getCount(); i++) {
                    BodyPart bodyPart =  (BodyPart) multipart.getBodyPart(i);
                    result.addAll(getMimeMultipart(bodyPart));
                }
        }
        return result;
    }

我能够转发 email 不包括附件，但在转发附件/内联图像时遇到问题。
请帮我解决这个问题。

我能够将完整的邮件作为附件转发，如何按原样转发邮件。

MultiPartEmail email = new MultiPartEmail();
MimeMultipart mp = new MimeMultipart();
MimeBodyPart fmbp = new MimeBodyPart();
fmbp.setContent(message, "message/rfc822");
fmbp.setDisposition(Part.INLINE);
mp.addBodyPart(fmbp);
email.setContent(mp);

或者如果我使用代码

MimeMultipart mp = (MimeMultipart) message.getContent();
email.setContent(mp, message.getContentType());

我正在转发 email 就像转发编码邮件的截图一样

Answer 1

这里的情况是从一个邮件服务器读取邮件并将相同的消息发送到同一应用程序中的另一个 email id。

为此，我使用 Java 邮件 API 进行读取和发送。 如果您在两个步骤中使用不同的主机，请确保更新属性。

    private void sendMailJavax(Message oldMessage) {
        try { 
            // creating a new message using the older message
            MimeMessage message = new MimeMessage((MimeMessage)oldMessage);
            // updating properties as per sender Mailing API
            message.getSession().getProperties().clear();
            message.getSession().getProperties().setProperty("mail.smtp.host", forwardHost);

            // setting appropriate headers. // make sure you don't append using .add methods.
            message.setFrom(new InternetAddress(emailFrom));
            message.setRecipient(Message.RecipientType.TO, new InternetAddress(to));
            message.setReplyTo(new Address[] { new InternetAddress(replyToEmail)});

            Transport.send(message); 
            System.out.println("Email Sent  successfully...."); 
            } catch (MessagingException mex) { 
                mex.printStackTrace(); 
            } 
    }