在我的Spring Boot web应用程序中，如何在没有模板engine>的情况下发送包含html的电子邮件

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.mail.javamail.MimeMessageHelper;
import org.springframework.stereotype.Service;

import javax.mail.MessagingException;
import javax.mail.internet.MimeMessage;

@Service
public class EmailService {

    @Autowired
    private JavaMailSender javaMailSender;

    public void sendHtmlEmail(String to, String subject, String htmlContent) throws MessagingException {
        MimeMessage message = javaMailSender.createMimeMessage();
        MimeMessageHelper helper = new MimeMessageHelper(message, true);
        helper.setTo(to);
        helper.setSubject(subject);
        helper.setText(htmlContent, true);
        javaMailSender.send(message);
    }
}