在Java中发送消息时出现MessagingExceptionIOException？

Question

我使用以下代码发送邮件。文本消息发送正常，但带有附件的邮件不起作用，它给出了异常。

javax.mail.MessagingException：发送消息时发生IOException；嵌套的异常是：javax.activation.UnsupportedDataTypeException：MIME类型为multipart
/ mixed的无对象DCH；boundary =“ ---- = _ Part_0_10430987.1294298904906”在com.sun.mail.smtp.SMTPTransport.sendMessage（SMTPTransport.java:676）在javax.mail.Transport.send0（Transport.java:189）在javax.mail
Gmailer.GMailSender.sendMailAttach（GMailSender.java:114）上的.Transport.send（Transport.java:118）在SendMail.main（SendMail.java:22）上的原因：javax.activation.UnsupportedDataTypeException：没有用于MIME类型的对象DCH多份/混合
boundary =“ ---- = _ Part_0_1_10980987.1294298904906”在javax.activation.ObjectDataContentHandler.writeTo（Unknown
Source）在javax.activation.DataHandler。

带有附件代码的邮件：

public synchronized void sendMailAttach(String subject, String body,
    String sender, String recipients)  {
try {
    MimeMessage message = new MimeMessage(session);

    message.setSender(new InternetAddress(sender));
    message.setSubject(subject);

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

    // Fill the message
    messageBodyPart.setText("hi Demo");

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

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

    // Put parts in message
    message.setContent(multipart);

    if (recipients.indexOf(',') > 0)
        message.setRecipients(Message.RecipientType.TO,
                InternetAddress.parse(recipients));
    else
        message.setRecipient(Message.RecipientType.TO,
                new InternetAddress(recipients));
    Transport.send(message);

}
catch (MessagingException e) {
    System.out.println("MessagingException" + e.getMessage());
}
catch (Exception e) {
    System.out.println("Mail Send Exception " + e.getMessage());
}
 }

短信发送代码：

public synchronized void sendMail(String subject, String body,
    String sender, String recipients) throws Exception {
try {
    MimeMessage message = new MimeMessage(session);
    DataHandler handler = new DataHandler(new ByteArrayDataSource(
            body.getBytes(), "text/plain"));
    message.setSender(new InternetAddress(sender));
    message.setSubject(subject);
    message.setDataHandler(handler);
    if (recipients.indexOf(',') > 0)
        message.setRecipients(Message.RecipientType.TO,
                InternetAddress.parse(recipients));
    else
        message.setRecipient(Message.RecipientType.TO,
                new InternetAddress(recipients));
    Transport.send(message);
} catch (Exception e) {

}
}

Answer 1

首先，您可以使用MimeBodyPart.attachFile()而不是亲自对DataSource/
DataHandler代码进行整理，从而使代码更加简洁。

其次，尝试使用适当的值在附件部分上设置Content-Type和Content- Disposition标头。（attachFile默认情况下，将为您设置Content-Disposition。）例如，

messageBodyPart = new MimeBodyPart();
messageBodyPart.attachFile(new File("mail.txt"));
messageBodyPart.setHeader("Content-Type", "text/plain; charset=\"us-ascii\"; name=\"mail.txt\"");

编辑：

经过一番思考，这在类加载时一定是不对的。请检查其他SO线程以查看它是否可以解决您的情况。（一般问题：可能是您的类路径中有一个额外的activation.jar；也有其他可能导致它。）