如何使用IMAP和JavaMail更快地从GMAIL下载电子邮件？

Question

如何使用IMAP和JavaMail更快地从GMAIL下载电子邮件？ 我可以使用IMAP进行批量下载吗？ 我也将电子邮件保存到MongoDB中。 我看到一些网站正在迅速做到这一点。

我可以在这里使用任何性能提示。

----------------------------------------------- ------

        // Get inbox folder
        Folder inbox = store.getFolder("inbox");
        // SET readonly format (*You can set read and write)
        inbox.open(Folder.READ_ONLY);

        // Display email Details

        // Inbox email count
        int messageCount = inbox.getMessageCount();
        System.out.println("Total Messages in INBOX:- " + messageCount);

        Message[] messages = inbox.getMessages(1, messageCount);

        long startTime = System.currentTimeMillis();

        // Fetch only necessary headers for each message
        FetchProfile profile = new FetchProfile();
        profile.add(FetchProfile.Item.ENVELOPE);
        profile.add(FetchProfile.Item.FLAGS);
        profile.add(FetchProfile.Item.CONTENT_INFO);
        if (inbox instanceof UIDFolder) {
            profile.add(UIDFolder.FetchProfileItem.UID);
        }
        inbox.fetch(messages, profile);

        System.out
                .println("Time elapsed while fetching message headers;" + (System.currentTimeMillis() - startTime));

        ArrayList<Email> al = new ArrayList<Email>();
        for (int i = 1; i < messageCount; i++) {
            //System.out.println("------------------------------------------------------------");
            Email email = new Email();
            email.setId(i + "");
            email.setSenderAddress(extractEmail(messages[i].getFrom()[0].toString()));
            email.setReceivedDate(messages[i].getReceivedDate());
            email.setSentDate(messages[i].getSentDate());
            email.setSubject(messages[i].getSubject());
            email.setMessageContent(messages[i].getContent().toString());

            email.setReceiverAddresses(new String[messages[i].getAllRecipients().length]);
            for (int j = 0; j < messages[i].getAllRecipients().length; j++)
                email.getReceiverAddresses()[j] = extractEmail(
                        messages[i].getAllRecipients()[j].toString());

            al.add(email);
            if (i % 2000 == 0) {
                emailMongoRepository.save(al);
                System.out.println("----------Bulk Save--------------------------------------------------");
                al = new ArrayList<Email>();
            }
        }

        inbox.close(true);
        store.close();

        System.out.println("Time elapsed while fetching message headers;" + (System.currentTimeMillis() - startTime));

    } catch (Exception e) {
        e.printStackTrace();
    }