附件文件名字符集-JavaMail更新后的问题

Question

Content-Type: application/octet-stream; name="Frammøtebekreftelse.pdf"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="Frammøtebekreftelse.pdf"

使用JavaMail1.6.2，我们有这样的体验：

Content-Type: application/octet-stream; 
    name*=windows-1252''Framm%F8tebekreftelse.pdf
Content-Transfer-Encoding: base64
Content-Disposition: attachment; 
    filename*=windows-1252''Framm%F8tebekreftelse.pdf

我认为这是好的，但是接收方在name*-格式上有问题，这导致我们使用encodeParameters=false。

使用JavaMail 1.6.2和encodeParameters=false，我们有这样的体验：

Content-Type: application/octet-stream; name="Frammøtebekreftelse.pdf"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="Frammøtebekreftelse.pdf"

这个代码很简单。下面是一个MCVE，它应该演示这个问题：

import java.io.IOException;
import java.util.Properties;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.AddressException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;

public class Mcve {
    public static void main(String[] args) throws AddressException, MessagingException, IOException {
        Properties props = System.getProperties();
        props.setProperty("mail.smtp.host", "localhost");
        props.setProperty("mail.mime.encodeparameters", "false");

        Session session = Session.getInstance(props, null);
        MimeMessage message = new MimeMessage(session);

        message.setFrom(new InternetAddress("[e-mail]"));
        message.setRecipients(Message.RecipientType.TO, InternetAddress.parse("[e-mail]", false));
        message.setSubject("Frammøtebekreftelse");

        MimeMultipart multipart = new MimeMultipart();

        MimeBodyPart body = new MimeBodyPart();
        body.setContent("Hello world", "text/plain");
        multipart.addBodyPart(body);

        MimeBodyPart attachment = new MimeBodyPart();
        attachment.attachFile("Frammøtebekreftelse.pdf");
        multipart.addBodyPart(attachment);

        message.setContent(multipart);

        Transport.send(message);
    }
}

Answer 1

为了获得JavaMail1.6.2中头的旧外观，我需要添加以下两个系统属性：

props.setProperty("mail.mime.encodeparameters", "false");
props.setProperty("mail.mime.allowutf8", "false");

修补程序注释中对mail.mime.allowUTF8的解释：

mail.mime.allowutf8:

  If set to "true", UTF-8 strings are allowed in message headers,
  e.g., in addresses.  This should only be set if the mail server also
  supports UTF-8.

不幸的是，我对此并不完全有信心，不会搞砸其他一些功能。根据我的基本检查，区别至少在于LineOutputStream中的以下功能。

public void writeln(String s) throws IOException {
    byte[] bytes = ASCIIUtility.getBytes(s);
    out.write(bytes);
    out.write(newline);
}

public void writeln(String s) throws IOException {
    byte[] bytes;
    if (allowutf8)
        bytes = s.getBytes(StandardCharsets.UTF_8);
    else
        bytes = ASCIIUtility.getBytes(s);
    out.write(bytes);
    out.write(newline);
}