当电子邮件有附件时发出阅读电子邮件正文？

Question

我找到了一个很好的代码来从我的收件箱电子邮件服务器读取电子邮件，该代码工作正常，但有几个问题：

我需要截取每封邮件的正文，但是当邮件有附件时，我收到这样的字符串javax.mail.internet.MimeMultipart@100363 ，或 com.sun.mail.util.BASE64DecoderStream@14e8cee，而不是正文消息。如果电子邮件只是纯文本且没有附件，则效果很好。似乎我不是唯一遇到此问题的人，我一直在网上阅读但找不到解决方案。
我想忽略大小超过 4 MB 的附件。

下面是 class，如有任何意见，我将不胜感激。重要的是要说我是 java 中的新手程序员。提前致谢！

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
import javax.mail.Address;
import javax.mail.BodyPart;
import javax.mail.Flags;
import javax.mail.Folder;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Multipart;
import javax.mail.NoSuchProviderException;
import javax.mail.Part;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Store;
import javax.mail.Flags.Flag;
import javax.mail.search.FlagTerm;

public class ReadMailSample {
    Properties properties = null;
    private Session session = null;
    private Store store = null;
    private Folder inbox = null;
    private String userName; 
    private String password;
    String downloadDirectory = "D:/Attachment/";

    public ReadMailSample() {
        userName = "myemail@domain.com";// provide user name
        password = "mypassword";// provide password
    }

    public void readMails() {
        properties = new Properties();
        properties.setProperty("mail.host", "imap.secureserver.net");
        properties.setProperty("mail.port", "110");
        properties.setProperty("mail.transport.protocol", "imap");
        session = Session.getInstance(properties,
                new javax.mail.Authenticator() {
                    protected PasswordAuthentication getPasswordAuthentication() {
                        return new PasswordAuthentication(userName, password);
                    }
                });
        try {
            store = session.getStore("imap");
            store.connect();
            inbox = store.getFolder("INBOX");
            inbox.open(Folder.READ_WRITE);
            Message messages[] = inbox.search(new FlagTerm(
                    new Flags(Flag.SEEN), false));
            ;
            System.out.println("Number of mails = " + messages.length);
            for (int i = 0; i < messages.length; i++) {
                Message message = messages[i];
                Address[] from = message.getFrom();
                System.out.println("--> ** E-mail No. "+ i + " **");
                System.out.println("-------------------------------");
                System.out.println("Date : " + message.getSentDate());
                System.out.println("From : " + from[0]);
                System.out.println("Subject: " + message.getSubject());
                System.out.println("Content :");
                processMessageBody(message);
                System.out.println("--------------------------------");

            }
            inbox.close(true);
            store.close();
        } catch (NoSuchProviderException e) {
            e.printStackTrace();
        } catch (MessagingException e) {
            e.printStackTrace();
        }
    }

    public void processMessageBody(Message message) {
        try {
            Object content = message.getContent();
            // check for string
            // then check for multipart
            if (content instanceof String) {
                System.out.println(content);
            } else if (content instanceof Multipart) {
                System.out.println(content);
                Multipart multiPart = (Multipart) content;
                procesMultiPart(multiPart);
            } else if (content instanceof InputStream) {
                InputStream inStream = (InputStream) content;
                int ch;
                while ((ch = inStream.read()) != -1) {
                    System.out.write(ch);
            }
            }

        } catch (IOException e) {
            e.printStackTrace();
        } catch (MessagingException e) {
            e.printStackTrace();
        }
    }

    public void procesMultiPart(Multipart content) {

        try {

            for (int i = 0; i < content.getCount(); i++) {
                BodyPart bodyPart = content.getBodyPart(i);
                Object o;

                o = bodyPart.getContent();
                if (o instanceof String) {
                    System.out.println("Text = " + o);
                } else if (null != bodyPart.getDisposition()
                        && bodyPart.getDisposition().equalsIgnoreCase(
                                Part.ATTACHMENT)) {
                    String fileName = bodyPart.getFileName();
                    System.out.println("Text = " + o);
                    System.out.println("fileName = " + fileName);
                    InputStream inStream = bodyPart.getInputStream();
                    FileOutputStream outStream = new FileOutputStream(new File(
                            downloadDirectory + fileName));
                    byte[] tempBuffer = new byte[4096];// 4 KB
                    int numRead;
                    while ((numRead = inStream.read(tempBuffer)) != -1) {
                        outStream.write(tempBuffer);
                    }
                    inStream.close();
                    outStream.close();
                }
                // else?

            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (MessagingException e) {
            e.printStackTrace();
        }

    }

    public static void main(String[] args) {
        ReadMailSample sample = new ReadMailSample();
        sample.readMails();
    }
}

Answer 1

来自 JavaMail 常见问题解答：
- How do I find the main message body in a message that has attachments?
定义 "ignore"。你看到getSize method了吗？

当电子邮件有附件时发出阅读电子邮件正文？

Issue reading email body when email has attachments?

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