java将邮件附件从远程文件服务器拿下来，并且实现该附件的邮件发送

如果要从远程文件服务器拿取附件并将其作为邮件的附件发送，可以使用Java的URL类和URLConnection类来实现。以下是一个示例代码，可以实现从远程文件服务器获取附件并将其作为附件添加到邮件中并发送邮件：

import java.io.*;
import java.net.*;
import java.util.*;
import javax.activation.*;
import javax.mail.*;
import javax.mail.internet.*;

public class SendEmailWithRemoteAttachment {
    public static void main(String[] args) {
        // 远程文件信息
        String remoteFileURL = "http://example.com/file.txt";
        String remoteFileName = "file.txt";

        // 邮件信息
        String host = "smtp.example.com";
        String from = "your-email@example.com";
        String password = "your-email-password";
        String to = "recipient@example.com";
        String subject = "Email with Remote Attachment";
        String body = "Please see the attached file.";

        // 设置邮件属性
        Properties props = new Properties();
        props.put("mail.smtp.host", host);
        props.put("mail.smtp.auth", "true");

        // 创建Session
        Session session = Session.getInstance(props,
          new javax.mail.Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(from, password);
            }
          });

        try {
            // 获取远程文件
            URL url = new URL(remoteFileURL);
            URLConnection conn = url.openConnection();
            InputStream is = conn.getInputStream();

            // 创建邮件对象
            MimeMessage message = new MimeMessage(session);
            message.setFrom(new InternetAddress(from));
            message.setRecipients(Message.RecipientType.TO,
                InternetAddress.parse(to));
            message.setSubject(subject);

            // 创建邮件内容
            Multipart multipart = new MimeMultipart();
            BodyPart messageBodyPart = new MimeBodyPart();
            messageBodyPart.setText(body);
            multipart.addBodyPart(messageBodyPart);

            // 创建附件
            messageBodyPart = new MimeBodyPart();
            DataSource source = new ByteArrayDataSource(is, "application/octet-stream");
            messageBodyPart.setDataHandler(new DataHandler(source));
            messageBodyPart.setFileName(remoteFileName);
            multipart.addBodyPart(messageBodyPart);

            // 设置邮件内容
            message.setContent(multipart);

            // 发送邮件
            Transport.send(message);

            System.out.println("Email with Remote Attachment sent successfully!");
        } catch (MessagingException | IOException e) {
            throw new RuntimeException(e);
        }
    }
}

需要注意的是，这个示例代码中的远程文件地址、远程文件名、邮件服务器地址、发件人邮箱、发件人邮箱密码、收件人邮箱需要根据实际情况进行修改。