Question

我正在尝试使用javax api在另一封邮件中将邮件作为附件发送。截至目前，我首先将邮件保存在磁盘上，然后使用以下代码将其附加到另一封电子邮件： -

        MimeMessage generateMailMessage = new MimeMessage(getMailSession);
        generateMailMessage.setFrom(new InternetAddress("abc@a.com"));
        String mailSubject = properties.getProperty("mail.subject");
        generateMailMessage
                .setSubject(mailSubject);
        generateMailMessage.setContent(emailBody, "text/html");
        generateMailMessage.addRecipient(Message.RecipientType.TO,
                new InternetAddress(properties.getProperty("message.recipienttype.to")));
        generateMailMessage.addRecipient(Message.RecipientType.CC,
                new InternetAddress(recipientEmail));


        File  file = new File(properties.getProperty("mail.draft.folder")+"mail.eml");
        FileOutputStream fos = new FileOutputStream(chatFile);
        generateMailMessage.writeTo(fos);

        Session getMailSession1 = Session.getDefaultInstance(mailServerProperties, null);

        MimeMessage generateMailMessage1 = new MimeMessage(getMailSession1);
        generateMailMessage1
                .setSubject("Attachment");

        generateMailMessage1.addRecipient(Message.RecipientType.TO,
                new InternetAddress("manish@xyz.com"));


        Multipart multipart = new MimeMultipart();
        MimeBodyPart messageBodyPart = new MimeBodyPart();
        messageBodyPart.setDescription("hahdsa");
        DataSource source = new FileDataSource(file);
        messageBodyPart.setDataHandler(new DataHandler(source));
        messageBodyPart.setFileName("mail.eml");
        multipart.addBodyPart(messageBodyPart);
        generateMailMessage1.setContent(multipart);


        transport = getMailSession1.getTransport("smtp");
        if(!transport.isConnected())
            transport.connect(properties.getProperty("mail.host"),
                Integer.parseInt((String) properties.get("mail.smtp.port")), "abc@xyz.com",
                (String) properties.get("mail.password"));



        transport.sendMessage(generateMailMessage1, generateMailMessage1.getAllRecipients());
        transport.close();

有没有办法可以在不保存附加电子邮件的情况下执行相同的操作。我搜索过但发现要附加的文件可以存储在内存中，但无法将邮件保存在内存中。

请建议。

由于

Answer 1

您可以将附加的电子邮件写入FileOutputStream但不能写入ByteArrayOutputStream，以便电子邮件保留在RAM中。然后，您可以将流转换为字节数组并发送它。像这样的东西（它不是下面的纯Java代码，没有异常处理，关闭流等，它只是一个说明这个想法的伪代码）：

...
ByteArrayOutputStream emailOutputStream = new ByteArrayOutputStream();
generateMailMessage.writeTo(emailOutputStream);
...
MimeBodyPart messageBodyPart = new MimeBodyPart();
...
byte[] email = emailOutputSteam.toByteArray();
messageBodyPart.setDataHandler(email);
...

唯一关心的问题是如何将电子邮件数据附加到邮件正文。我不熟悉您使用的电子邮件API。也许可以指定一个字节数组作为MimeBodyPart.setDataHandler()方法的参数，可能不是。但MimeBodyPart.setDataHandler()方法很可能接受蒸汽（BTW大多数Java库不仅可以从文件中读取，还可以从输入流中读取）。在这种情况下，ByteArrayInputStream会有所帮助，如下图所示：

...
ByteArrayOutputStream emailOutputStream = new ByteArrayOutputStream();
generateMailMessage.writeTo(emailOutputStream);
...
MimeBodyPart messageBodyPart = new MimeBodyPart();
...
ByteArrayInputStream emailInputStream = ByteArrayInputStream(emailOutputSteam.toByteArray());
messageBodyPart.setDataHandler(emailInputStream);
...

<强>更新

哦，我明白了...... setDataHandler()接受DataHandler。并DataHandler接受DataSource！

但是让我们看一下DataSource's Javadoc。已经提供了两种实现：FileDataSource和URLDataSource。实现从字节数组中获取数据的新数据源并不困难。只需要实施几种方法。同样，下面的代码大大简化了。但它带来了数据流是通用概念的想法。一旦您实现了DataSource接口DataHandler，类甚至不会注意到实际上数据是针对RAM（或数据库，或其他）采取的：

public class ByteArrayInputStreamDataSource {

    private ByteArrayInputStream stream;

    public ByteArrayInputStreamDataSource(byte[] data) {
        this.stream = new ByteArrayInputStream(data);
    }

    public String getContentType() {
        return "Your content MIME type, perhaps, it will be text/html ...";
    }

    public InputStream getInputStream() {
        return stream;
    }       

    public String getName() {
        return "Some meaningful name";
    }

    public OutputStream getOutputStream() {
        throw new UnsupportedOperationException("Modification of the datasource is not allowed.");
    }

    public void close() {
        // This method is not required by DataSource interface. 
        // But once we deal with stream generally it will be better 
        // to put here logic that closes the stream gracefully.
        // As for ByteArrayInputStream there is no need to close it 
        // according to Javadoc:
        // https://docs.oracle.com/javase/7/docs/api/java/io/ByteArrayInputStream.html#close()
    }
}

所以我们的自定义数据源可以像这样使用：

...
ByteArrayOutputStream emailOutputStream = new ByteArrayOutputStream();
generateMailMessage.writeTo(emailOutputStream);
...
MimeBodyPart messageBodyPart = new MimeBodyPart();
...
DataSource byteArraySource = new ByteArrayInputStream(emailOutputStream.toByteArray());
messageBodyPart.setDataHandler(new DataHandler(byteArraySource));
...

如何将邮件作为附件发送到java中的另一个邮件而不将其保存到磁盘

1 个答案: