Java Jakarta Mail not accepting emoji on subject

Question

I´m trying to send alerts through jakarta mail, using a gmail account and for this I wanted to send a emoji on the subject.

Session session = Session.getInstance(properties, new Authenticator() {
    @Override
    protected PasswordAuthentication getPasswordAuthentication() {
        return new PasswordAuthentication(usr, pass);
    }
});

try {
    Message message = new MimeMessage(session);
    message.setFrom(new InternetAddress("[email protected]"));

    Address[] toUser = InternetAddress
            .parse(toEmail);

    message.setRecipients(Message.RecipientType.TO, toUser);
    message.setSubject("\uD83D\uDEA8"+" This is an alert "+"\uD83D\uDEA8");
    message.setContent(messageText, "text/html; charset=utf-8");

    Transport.send(message);
}

I´ve tried every answer about this but I receive a ? every time I try to send it via tomcat server, using a psvm it is functional to use something like "\uD83D\uDEA8"+" This is an alert "+"\uD83D\uDEA8".

Answer 1

Don't upcast MimeMessage to Message. MimeMessage has a method MimeMessage.setSubject(String subject, String charset) which takes the charset as an additional parameter.

Session session = Session.getInstance(properties, new Authenticator() {
    @Override
    protected PasswordAuthentication getPasswordAuthentication() {
        return new PasswordAuthentication(usr, pass);
    }
});

try {
    MimeMessage message = new MimeMessage(session);
    message.setFrom(new InternetAddress("[email protected]"));

    Address[] toUser = InternetAddress
            .parse(toEmail);

    message.setRecipients(Message.RecipientType.TO, toUser);
    message.setSubject("\uD83D\uDEA8"+" This is an alert "+"\uD83D\uDEA8", "UTF-8");
    message.setContent(messageText, "text/html; charset=utf-8");

    Transport.send(message);
}