如何在java中将现有HTML文件的内容原样发送到电子邮件正文中

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.util.Properties;

import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Multipart;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;

public class SendHtmlEmail {
    public static void main(String[] args) {
        // 读取HTML文件的内容
        String htmlContent = readHtmlFile("path/to/html/file.html");

        // 创建邮件内容
        MimeMessage message = createEmail(htmlContent);

        // 发送邮件
        sendEmail(message);
    }

    private static String readHtmlFile(String filePath) {
        StringBuilder content = new StringBuilder();
        try {
            File file = new File(filePath);
            BufferedReader reader = new BufferedReader(new FileReader(file));
            String line;
            while ((line = reader.readLine()) != null) {
                content.append(line);
            }
            reader.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return content.toString();
    }

    private static MimeMessage createEmail(String htmlContent) {
        Properties properties = System.getProperties();
        properties.setProperty("mail.smtp.host", "smtp.example.com"); // 设置邮件服务器地址
        properties.setProperty("mail.smtp.port", "25"); // 设置邮件服务器端口号

        Session session = Session.getDefaultInstance(properties);

        try {
            MimeMessage message = new MimeMessage(session);
            message.setFrom(new InternetAddress("sender@example.com")); // 设置发件人
            message.addRecipient(Message.RecipientType.TO, new InternetAddress("recipient@example.com")); // 设置收件人
            message.setSubject("HTML Email"); // 设置邮件主题

            Multipart multipart = new MimeMultipart();
            MimeBodyPart htmlPart = new MimeBodyPart();
            htmlPart.setContent(htmlContent, "text/html"); // 设置HTML内容
            multipart.addBodyPart(htmlPart);

            message.setContent(multipart);

            return message;
        } catch (MessagingException e) {
            e.printStackTrace();
        }
        return null;
    }

    private static void sendEmail(MimeMessage message) {
        try {
            Transport.send(message);
            System.out.println("Email sent successfully.");
        } catch (MessagingException e) {
            e.printStackTrace();
        }
    }
}