IdleManager uses the optional IMAP IDLE command (RFC 2177) to watch multiple folders for new messages. IdleManager uses an Executor to execute tasks in separate threads. An Executor is typically provided by an ExecutorService. For example, for a Java SE application:

	ExecutorService es = Executors.newCachedThreadPool();
	final IdleManager idleManager = new IdleManager(session, es);
 

For a Java EE 7 application:

	@Resource
	ManagedExecutorService es;
	final IdleManager idleManager = new IdleManager(session, es);
 

To watch for new messages in a folder, open the folder, register a listener, and ask the IdleManager to watch the folder:

	Folder folder = store.getFolder("INBOX");
	folder.open(Folder.READ_WRITE);
	folder.addMessageCountListener(new MessageCountAdapter() {
	    public void messagesAdded(MessageCountEvent ev) {
		Folder folder = (Folder)ev.getSource();
		Message[] msgs = ev.getMessages();
		System.out.println("Folder: " + folder +
		    " got " + msgs.length + " new messages");
		try {
		    // process new messages
		    idleManager.watch(folder); // keep watching for new messages
		} catch (MessagingException mex) {
		    // handle exception related to the Folder
		}
	    }
	});
	idleManager.watch(folder);
 

This delivers the events for each folder in a separate thread, NOT using the Executor. To deliver all events in a single thread using the Executor, set the following properties for the Session (once), and then add listeners and watch the folder as above.

	// the following should be done once...
	Properties props = session.getProperties();
	props.put("mail.event.scope", "session"); // or "application"
	props.put("mail.event.executor", es);
 

Note that, after processing new messages in your listener, or doing any other operations on the folder in any other thread, you need to tell the IdleManager to watch for more new messages. Unless, of course, you close the folder.

The IdleManager is created with a Session, which it uses only to control debug output. A single IdleManager instance can watch multiple Folders from multiple Stores and multiple Sessions.

Due to limitations in the Java SE nio support, a SocketChannel must be used instead of a Socket to connect to the server. However, SocketChannels don't support all the features of Sockets, such as connecting through a SOCKS proxy server. SocketChannels also don't support simultaneous read and write, which means that the idle method can't be used if SocketChannels are being used; use this IdleManager instead. To enable support for SocketChannels instead of Sockets, set the mail.imap.usesocketchannels property in the Session used to access the IMAP Folder. (Or mail.imaps.usesocketchannels if you're using the "imaps" protocol.) This will effect all connections in that Session, but you can create another Session without this property set if you need to use the features that are incompatible with SocketChannels.