Javax Mail Untitled attachment in Outlook

Question

I try to make a java mail sending app, but when i add a .docx attachment Outlook show: "Untitled attachment xxxx.docx" My code:

MimeMessage message = new MimeMessage(session); // Message
message.setHeader("Content-Type", "text/html; charset=UTF-8");
message.setFrom(new InternetAddress(from));
message.addRecipient(Message.RecipientType.TO, address);
message.setSubject(subject, "UTF-8");
Multipart multipart = new MimeMultipart(); // body
BodyPart messageBodyPart = new MimeBodyPart();
messageBodyPart.setContent(body, "text/html; charset=utf-8"); //html body text
multipart.addBodyPart(messageBodyPart); // body add html text
if(file != null) {
    for (File f : file) {
        MimeBodyPart attachPart = new MimeBodyPart();
        attachPart.attachFile(f.getAbsolutePath(), MimeTypeUtils.getContentTypeByFileName(f.getName()), "base64");
//                attachPart.setFileName(f.getName());
        multipart.addBodyPart(attachPart); // body add attachment
    }
}
message.setContent(multipart); // message add body content
Transport.send(message);

There are problem only with a small amount of .docx file, but it's annoying. Someone can help me? And the "getContentTypeByFileName":

public class MimeTypeUtils {
    private static final Map<String, String> fileExtensionMap;
    static {
        fileExtensionMap = new HashMap<>();
        fileExtensionMap.put("docx", "application/vnd.openxmlformats-officedocument.wordprocessingml.document");
    }
    public static String getContentTypeByFileName(String fileName) {
        FileNameMap mimeTypes = URLConnection.getFileNameMap();
        String contentType = "";
        contentType = mimeTypes.getContentTypeFor(fileName);
        if (contentType == null || contentType.isEmpty()) {
            String extension = FilenameUtils.getExtension(fileName);
            contentType = fileExtensionMap.get(extension);
        }
        return contentType;
    }
}

Answer 1

I have a problem in encapsulation the MimeMesage. My old sollution:

MimeMessage { // the whole message
    Multipart{
        BodyPart // here is the body
        MimeBodyPart //this is the attachment
    }
}

But the correct way is:

MimeMessage {
    Multipart {
        MimeBodyPart {
            MimeBodyPart // plain text of body
            MimeBodyPart // html text of body
        }
        MimeBodyPart // attachment
        MimeBodyPart // attachment2 ...
    }
}

Code example:

MimeMessage message = new MimeMessage(session);
message.addHeader("Content-Type", "multipart/mixed; charset=UTF-8");

Multipart multipart = new MimeMultipart("alternative");

MimeBodyPart messageBodyPartPlain = new MimeBodyPart();
messageBodyPartPlain.setContent("Plain body text", "text/plain; charset=utf-8");
multipart.addBodyPart(messageBodyPartPlain);

MimeBodyPart messageBodyPart = new MimeBodyPart();
messageBodyPart.setContent("Html body text", "text/html; charset=utf-8");
multipart.addBodyPart(messageBodyPart);

MimeBodyPart mbp = new MimeBodyPart();
mbp.setContent(multipart);

Multipart mp2 = new MimeMultipart("mixed");
mp2.addBodyPart(mbp);

for (Attachment a : attachments) {
    if (a != null && a.getFile() != null) {
        MimeBodyPart mbp2 = new MimeBodyPart();
        FileDataSource fds = new FileDataSource(a.getFile()) {
            public String getContentType() {
                return MimeTypeUtils.getContentTypeByFileName(a.getName());
            }
        };
        mbp2.setDataHandler(new DataHandler(fds));
        mbp2.setFileName(a.getName());
        mp2.addBodyPart(mbp2);
    }
}

message.setContent(mp2);

And after this change, everything working correctly.