用java将文件附加到电子邮件

我想知道我做错了什么（我错过了什么）。我的电子邮件确实发送出去了，但没有附件。我正在发送的文件称为“日志”。正如您将看到的，我在这里尝试了多种方法，我也一个接一个地尝试了这些方法，但没有一种有效：

            MimeMessage message = new MimeMessage(session);
            MimeBodyPart emailAttachment = new MimeBodyPart();
            Multipart multipart = new MimeMultipart();
            int len = build.getLogFile().getPath().length();
            //I have verified that "file" provides the right path
            String file = build.getLogFile().getPath().substring(0, (len-3));
            String fileName = "log";
            DataSource source = new FileDataSource(file);
            emailAttachment.setDataHandler(new DataHandler(source));
            //I know this .attachFile is not needed but I added it when nothing was working
            emailAttachment.attachFile(build.getLogFile());
            emailAttachment.setFileName(fileName);
            multipart.addBodyPart(emailAttachment);
            message.setContent(multipart);  
            message.setFrom(adminAddress);
            message.setText(builder.toString());
            message.setSentDate(new Date());


            mailSender.send(message);

谢谢使用此代码=>

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

public class SendFileEmail
 {
 public static void main(String [] args)
{


  String to = "abcd@gmail.com";

  String from = "web@gmail.com";

  String host = "localhost";

  Properties properties = System.getProperties();

  properties.setProperty("mail.smtp.host", host);

  Session session = Session.getDefaultInstance(properties);

  try{

     MimeMessage message = new MimeMessage(session);

     message.setFrom(new InternetAddress(from));

     message.addRecipient(Message.RecipientType.TO,
                              new InternetAddress(to));

     message.setSubject("This is the Subject Line!");

     BodyPart messageBodyPart = new MimeBodyPart();

     messageBodyPart.setText("This is message body");

     Multipart multipart = new MimeMultipart();

     multipart.addBodyPart(messageBodyPart);

     messageBodyPart = new MimeBodyPart();
     String filename = "file.txt";
     DataSource source = new FileDataSource(filename);
     messageBodyPart.setDataHandler(new DataHandler(source));
     messageBodyPart.setFileName(filename);
     multipart.addBodyPart(messageBodyPart);


     message.setContent(multipart );


     Transport.send(message);
     System.out.println("Sent message successfully....");
  }catch (MessagingException mex) {
     mex.printStackTrace();
   }
}
}

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这可能有助于您确定所引用的文件是否存在并包含内容？除此之外，您的代码看起来还不错。我认为您应该尝试调试并逐行检查send方法。我确实通过尝试捕获文件是否为null来验证该文件是否存在。它不是空的。我可以手动转到该目录并找到名为log的文件。它有上下文，但没有文件扩展名。它没有文件扩展名这一事实会有所不同吗？