java将图像附件发送为。jpg而不是。使用JavaMail的文件

Question

在我的安卓应用程序中，我使用JavaMail发送一个.jpg图像作为附件，它工作正常，但问题是图像作为.file接收，而不是作为.jpg，我曾尝试使用messageBodyPart.setHeader("Content-ID","<image>");，但图像仍然作为.file接收。所以请帮助，我如何使我的代码以.jpg而不是.file的形式发送图像

代码：

import 安卓.content.Context;
import 安卓.os.AsyncTask;
import java.io.File;
import java.util.Properties;
import 安卓.os.Environment;
import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.activation.FileDataSource;
import javax.mail.Address;
import javax.mail.Authenticator;
import javax.mail.BodyPart;
import javax.mail.Message;
import javax.mail.PasswordAuthentication;
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 EmailHandler extends AsyncTask<Void, Void, Boolean> {

    private static String to = "receiver@gmail.com";
    private static String from = "senderp@gmail.com";
    private static String subject = "Subject";
    private static String sender = "Sender";
    private static String mail;
    private static String username = "sender";
    private static String password = "pasword";

    @Override
    protected Boolean doInBackground(Void... nothing) {
        try {
            Authenticator auth = new EmailAutherticator();
            Properties properties = new Properties();
            properties.setProperty("mail.smtp.auth", "true");
            properties.setProperty("mail.smtp.starttls.enable", "true");
            properties.setProperty("mail.smtp.host", "smtp.gmail.com");
            properties.setProperty("mail.smtp.port", "587");
            properties.setProperty("mail.smtp.user", username);
            properties.setProperty("mail.smtp.password", password);
            Session session = Session.getDefaultInstance(properties,auth);

            MimeMessage message = new MimeMessage(session);
            Address address = new InternetAddress(from,sender);
            message.setFrom(address);
            message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(to));
            message.setSubject(subject);
            message.setText("JPG Image Test");
            MimeMultipart multipart = new MimeMultipart();

            MimeBodyPart messageBodyPart = new MimeBodyPart();
            String pic = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES)+ File.separator+"picture0"+".jpg";
            DataSource source = new FileDataSource(pic);
            messageBodyPart.setDataHandler(new DataHandler(source0));
            messageBodyPart.setHeader("Content-ID","<image>");
            messageBodyPart.setFileName("Theft back");
            multipart.addBodyPart(messageBodyPart);

            message.setContent(multipart);
            Transport.send(message);
            return true;
        }
        catch(Exception exp) {
            exp.printStackTrace();
            return false;
        }
    }
}

class EmailAutherticator extends Authenticator {

    private String username = "sender";
    private String password = "password";

    public EmailAutherticator() {
        super();
    }

    public EmailAutherticator(String user,String pwd){
        super();
        username = user;
        password = pwd;
    }

    public PasswordAuthentication getPasswordAuthentication(){
        return new PasswordAuthentication(username,password);
    }

}

Answer 1

将.jpg扩展名添加到文件名

messageBodyPart.setFileName("Theft back.jpg");

而不是

messageBodyPart.setFileName("Theft back");