springboot 下载邮件

要在Spring Boot中下载邮件，你可以使用JavaMail API来实现。以下是一个简单的示例代码，可以下载并保存邮件附件。

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Properties;

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.Session;
import javax.mail.Store;

public class DownloadMailAttachments {

    public static void main(String[] args) throws MessagingException, IOException {
        String host = "mail.example.com";
        String username = "username";
        String password = "password";
        String downloadDirectory = "/path/to/download/directory";
        
        Properties properties = new Properties();
        properties.setProperty("mail.store.protocol", "imaps");

        Session session = Session.getInstance(properties, null);
        Store store = session.getStore();
        store.connect(host, username, password);

        Folder inboxFolder = store.getFolder("INBOX");
        inboxFolder.open(Folder.READ_WRITE);

        Message[] messages = inboxFolder.getMessages();
        System.out.println("Total Messages: " + messages.length);

        for (int i = 0; i < messages.length; i++) {
            Message message = messages[i];
            String contentType = message.getContentType();
            String subject = message.getSubject();

            if (contentType.contains("multipart")) {
                Multipart multiPart = (Multipart) message.getContent();
                int numberOfParts = multiPart.getCount();
                for (int partCount = 0; partCount < numberOfParts; partCount++) {
                    BodyPart bodyPart = multiPart.getBodyPart(partCount);
                    if (bodyPart.getDisposition() != null && bodyPart.getDisposition().equalsIgnoreCase("ATTACHMENT")) {
                        String fileName = bodyPart.getFileName();
                        InputStream inputStream = bodyPart.getInputStream();
                        Path filePath = Paths.get(downloadDirectory, fileName);
                        FileOutputStream outputStream = new FileOutputStream(filePath.toFile());

                        byte[] buffer = new byte[4096];
                        int bytesRead = -1;
                        while ((bytesRead = inputStream.read(buffer)) != -1) {
                            outputStream.write(buffer, 0, bytesRead);
                        }

                        outputStream.close();
                        inputStream.close();
                        System.out.println("Attachment " + fileName + " downloaded from email subject: " + subject);
                    }
                }
            }

            // Mark the message as deleted
            message.setFlag(Flags.Flag.DELETED, true);
        }

        // expunge deleted messages
        inboxFolder.close(true);
        store.close();
    }
}

你可以将上面的代码添加到你的Spring Boot应用程序中，然后替换`host`、`username`、`password`和`downloadDirectory`变量为相应的值，即可下载邮件。