如何使用指定的客户端以编程方式从Java发送电子邮件附件

import java.util.Properties;
import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.activation.FileDataSource;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Multipart;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.AddressException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;

public class SendEmailWithAttachment {

    public static void main(String[] args) {
        // 设置发件人、收件人和SMTP服务器信息
        String to = "recipient@example.com";
        String from = "sender@example.com";
        String host = "smtp.example.com";
        String port = "25";
        String username = "your_email_username";
        String password = "your_email_password";

        // 指定附件文件路径
        String attachmentFilePath = "/path/to/your/attachment/file.txt";

        // 设置邮件服务器属性
        Properties properties = new Properties();
        properties.put("mail.smtp.host", host);
        properties.put("mail.smtp.port", port);
        properties.put("mail.smtp.auth", "true");
        properties.put("mail.smtp.starttls.enable", "true");

        // 获取默认的Session对象
        Session session = Session.getInstance(properties, new javax.mail.Authenticator() {
            protected javax.mail.PasswordAuthentication getPasswordAuthentication() {
                return new javax.mail.PasswordAuthentication(username, password);
            }
        });

        try {
            // 创建一个默认的MimeMessage对象
            MimeMessage message = new MimeMessage(session);

            // 设置发件人和收件人
            message.setFrom(new InternetAddress(from));
            message.addRecipient(Message.RecipientType.TO, new InternetAddress(to));

            // 设置邮件主题和内容
            message.setSubject("Java Email with Attachment");
            message.setText("This is an email with attachment.");

            // 创建多部分邮件
            Multipart multipart = new MimeMultipart();

            // 创建一个存储附件的MimeBodyPart对象
            MimeBodyPart attachmentPart = new MimeBodyPart();
            DataSource source = new FileDataSource(attachmentFilePath);
            attachmentPart.setDataHandler(new DataHandler(source));
            attachmentPart.setFileName(attachmentFilePath.substring(attachmentFilePath.lastIndexOf("/") + 1));

            // 将附件添加到多部分邮件中
            multipart.addBodyPart(attachmentPart);

            // 将多部分邮件设置为邮件内容
            message.setContent(multipart);

            // 发送邮件
            Transport.send(message);
            System.out.println("Email sent with attachment.");
        } catch (MessagingException e) {
            e.printStackTrace();
        }
    }
}