class HasAttachment extends GenericMatcher {

    @Override
    public Collection<MailAddress> match(Mail mail) throws MessagingException {
        
        Exception anException = null;
        
        try {
            MimeMessage message = mail.getMessage();
            Object content;
            
            /**
             * if there is an attachment and no inline text,
             * the content type can be anything
             */
            if (message.getContentType() == null) {
                return null;
            }
            
            content = message.getContent();
            if (content instanceof Multipart) {
                Multipart multipart = (Multipart) content;
                for (int i = 0; i < multipart.getCount(); i++) {
                    try {
                        Part part = multipart.getBodyPart(i);
                        if (isAttachment(part)) {
                            return mail.getRecipients(); // file found
                        }
                    } catch (MessagingException e) {
                        anException = e;
                    } // ignore any messaging exception and process next bodypart
                }
            } else {
                if (isAttachment(message)) {
                    return mail.getRecipients(); // file found
                }
            }
        } catch (Exception e) {
            anException = e;
        }
        
        // if no attachment was found and at least one exception was catched rethrow it up
        if (anException != null) {
            throw new MessagingException("Malformed message", anException);
        }
        
        return null; // no attachment found
    }

}