IMAPExample.java

package de.sandstormmedia;

import com.sun.mail.imap.IMAPFolder;

import javax.mail.*;
import java.util.Properties;

/**
 * This example prints all messages (emails) from an IMAP-folder to the console.
 * <p/>
 * The messages are fetched in chunks of maximal 500 messages from latest message
 * to oldest message.
 */
public class IMAPExample {

	public static void main(String[] args) {
		String server = readLine("server", "imap.example.net");
		String username = readLine("username", "user@example.net");
		/*
		 * !!! NOTE: The password is displayed in the console and CAN BE READ by anyone watching. !!!
		 */
		String password = System.console().readLine("password: ");

		try {
			listMessages(server, username, password);
		} catch (Throwable e) {
			e.printStackTrace();
		}
	}

	private static String readLine(String message, String defaultValue) {
		String value = System.console().readLine(message + " (default: " + defaultValue + "): ");
		if (value.isEmpty()) {
			value = defaultValue;
		}
		return value;
	}

	private static void listMessages(String url, String username, String password) throws MessagingException {
		Properties props = System.getProperties();
		props.setProperty("mail.store.protocol", "imaps");
		Session session = Session.getDefaultInstance(props, null);
		Store store = session.getStore("imaps");
		try {
			System.out.println("Connecting to IMAP server: " + url);
			store.connect(url, username, password);

			Folder root = store.getDefaultFolder();
			Folder[] folders = root.list();
			System.out.println("Select a folder");
			for (int i = 0; i < folders.length; i++) {
				System.out.println("\t" + folders[i].getName());
			}

			String folderName = readLine("folder", "INBOX");
			IMAPFolder folder = (IMAPFolder) store.getFolder(folderName);

			long afterFolderSelectionTime = System.nanoTime();
			int totalNumberOfMessages = 0;
			try {
				if (!folder.isOpen()) {
					folder.open(Folder.READ_ONLY);
				}

				/*
				 * Now we fetch the message from the IMAP folder in descending order.
				 *
				 * This way the new mails arrive with the first chunks and older mails
				 * afterwards.
				 */
				long largestUid = folder.getUIDNext() - 1;
				int chunkSize = 500;
				for (long offset = 0; offset < largestUid; offset += chunkSize) {
					long start = Math.max(1, largestUid - offset - chunkSize + 1);
					long end = Math.max(1, largestUid - offset);

					/*
					 * The next line fetches the existing messages within the
					 * given range from the server.
					 *
					 * The messages are not loaded entirely and contain hardly
					 * any information. The Message-instances are mostly empty.
					 */
					long beforeTime = System.nanoTime();
					Message[] messages = folder.getMessagesByUID(start, end);
					totalNumberOfMessages += messages.length;
					System.out.println("found " + messages.length + " messages (took " + (System.nanoTime() - beforeTime) / 1000 / 1000 + " ms)");

					/*
					 * If we would access e.g. the subject of a message right away
					 * it would be fetched from the IMAP server lazily.
					 *
					 * Fetching the subjects of all messages one by one would
					 * produce many requests to the IMAP server and take too
					 * much time.
					 *
					 * Instead with the following lines we load some information
					 * for all messages with one single request to save some
					 * time here.
					 */
					beforeTime = System.nanoTime();
					// this instance could be created outside the loop as well
					FetchProfile metadataProfile = new FetchProfile();
					// load flags, such as SEEN (read), ANSWERED, DELETED, ...
					metadataProfile.add(FetchProfile.Item.FLAGS);
					// also load From, To, Cc, Bcc, ReplyTo, Subject and Date
					metadataProfile.add(FetchProfile.Item.ENVELOPE);
					// we could as well load the entire messages (headers and body, including all "attachments")
					// metadataProfile.add(IMAPFolder.FetchProfileItem.MESSAGE);
					folder.fetch(messages, metadataProfile);
					System.out.println("loaded messages (took " + (System.nanoTime() - beforeTime) / 1000 / 1000 + " ms)");

					/*
					 * Now that we have all the information we need, let's print some mails.
					 * This should be wicked fast.
					 */
					beforeTime = System.nanoTime();
					for (int i = messages.length - 1; i >= 0; i--) {
						Message message = messages[i];
						long uid = folder.getUID(message);
						boolean isRead = message.isSet(Flags.Flag.SEEN);

						if (!isRead) {
							// new messages are green
							System.out.print("\u001B[32m");
						}
						System.out.println("\t" + uid + "\t" + message.getSubject());
						if (!isRead) {
							// reset color
							System.out.print("\u001B[0m");
						}
					}
					System.out.println("Listed message (took " + (System.nanoTime() - beforeTime) / 1000 / 1000 + " ms)");
				}
			} finally {
				if (folder.isOpen()) {
					folder.close(true);
				}
			}

			System.out.println("\nListed all " + totalNumberOfMessages + " messages (took " + (System.nanoTime() - afterFolderSelectionTime) / 1000 / 1000 + " ms)");
		} finally {
			store.close();
		}
	}
}