附件名称编码失败

Question

我尝试发送带有附件（一个 pdf 文件）的电子邮件，但收件人收到了一个名称不同且没有 .pdf 结尾的文件。文件名是希腊文..

try {
    MimeMessage message = new MimeMessage(session);
    message.setFrom(new InternetAddress("from@mail.com"));
    message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(mail));
    message.setSubject(title,"utf-8");

    // 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 = "file.pdf";
    String f = name + " Πρόγραμμα Ιανουάριος 2016.pdf";  // the desired name of the file
    DataSource source = new FileDataSource(filename);
    messageBodyPart.setDataHandler(new DataHandler(source));
    messageBodyPart.setFileName(MimeUtility.encodeText(f, "UTF-8", null));
    multipart.addBodyPart(messageBodyPart);

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

    Transport.send(message);

    System.out.println("Mail " + mail +" sent");
} catch (MessagingException e) {
    throw new RuntimeException(e);
}

name 是一个字符串变量，之前正在获取一个值。奇怪的是，如果我有String f = name + " αααα.pdf"，接收者将成功获得一个名为Ρουβάς αααα.pdf 的pdf，但如果我有这个字符串f = name + " Πρόγραμμα Ιανουάριος 2016.pdf";，他没有。他越来越喜欢 =_UTF-8_B_zpzOtc Dz4POsc67zrHPgiDOmc6xzr3Ov8 FzqzPgc65zr_Pgi___ ___filename_1=__5wZGY=_=

我添加了message.writeTo(System.out);，我得到了：

MIME-Version: 1.0
Content-Type: multipart/mixed; 
    bou

    ndary="----=_Part_0_1825884453.1457025565509"

    ------=_Part_0_1825884453.1457025565509
    Content-Type: text/plain; charset=us-ascii
    Content-Transfer-Encoding: 7bit

    This is message body
    ------=_Part_0_1825884453.1457025565509
    Content-Type: application/octet-stream; 
        name*0="=?UTF-8?B?zpzOtc+Dz4POsc67zrHPgiDOmc6xzr3Ov8+FzrHPgc6vzr/Pgi"; 
        name*1="Ay?=
     =?UTF-8?B?MDE2zpnOsc69zr/Phc6sz4HOuc6/z4IgMjAxNi5wZGY=?"; 
        name*2="="
    Content-Transfer-Encoding: base64
    Content-Disposition: attachment; 
        filename*0="=?UTF-8?B?zpzOtc+Dz4POsc67zrHPgiDOmc6xzr3Ov8+FzrHPgc6vzr/Pgi"; 
        filename*1="Ay?=
     =?UTF-8?B?MDE2zpnOsc69zr/Phc6sz4HOuc6/z4IgMjAxNi5wZGY=?"; 
        filename*2="="

props.setProperty("mail.mime.encodeparameters", "false"); 或 true

MIME-Version: 1.0
Content-Type: multipart/mixed; 
    boundary="----=_Part_0_797681969.1457074816557"

------=_Part_0_797681969.1457074816557
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit

This is message body
------=_Part_0_797681969.1457074816557
Content-Type: application/octet-stream; name="?????????? 2016.pdf"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; 
    filename*=Cp1252''%3F%3F%3F%3F%3F%3F%3F%3F%3F%3F%202016.pdf

Answer 1

因为您自己对文件名进行编码，所以您使用的是非标准 MIME 编码格式，如 JavaMail FAQ 中所述。然后使用标准 RFC 2231 技术将该非标准编码文本拆分为多个参数。正是这种非标准格式和标准格式的混合可能会导致邮件阅读器感到困惑。

尝试通过删除对MimeUtility.encodeText 的调用让JavaMail 为您进行编码。如果这不起作用，请将系统属性 mail.mime.encodeparameters 设置为 false 以禁用 RFC 2231 编码。