如何为带有附件的Java MimeMessage对象创建测试数据？

Question

I want to persist mails in a database. To test it, I try to generate some test MimeMessage objects with and without attachments. I add the attachments like this:

MimeMessage message = new MimeMessage(Session.getDefaultInstance(props, null));
Multipart multipart = new MimeMultiPart();
MimeBodyPart bodyPart = new MimeBodyPart();

bodyPart.attachFile("./files/test.txt");
bodyPart.setFileName("test.txt");

multipart.addBodyPart(bodyPart);
message.setContent(multipart);
message.saveChanges();

Now I want to serialize this MimeMessage with its writeTo(OutputStream) method. That call results in a FileNotFoundException:

java.io.FileNotFoundException: ./files/test.txt: open failed: ENOENT (No such file or directory)

It seems like the writeTo() -Method is searching for the attached files. Shouldn't the files already be contained inside the MimeMessage-Object, through the attachFile() -call in my test data generator? Do I have to do something with the MimeMessage-Object to be able to serialize it like that?

Answer 1

Try using a File object, where you can check if that file exists.

private static BodyPart createAttachment(filepath) {
    File file = new File(filepath);
    if (file.exists()) {
        DataSource source = new FileDataSource(file);
        DataHandler handler = new DataHandler(source);
        BodyPart attachment = new MimeBodyPart();
        attachment.setDataHandler(handler);
        attachment.setFileName(file.getName());
        return attachment;
    }
    return null; // or throw exception
}

I noticed that you're providing a relative path to a file (starting with a dot "."). That only works if the file is in the same directory (or a subdirectory in your case) where your application is executing from. Try using an absolute path instead.