Class IdleManager


  • public class IdleManager
    extends java.lang.Object
    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.

    NOTE: The IdleManager, and all APIs and properties related to it, should be considered EXPERIMENTAL. They may be changed in the future in ways that are incompatible with applications using the current APIs.

    Since:
    JavaMail 1.5.2
    • Constructor Summary

      Constructors 
      Constructor Description
      IdleManager​(Session session, java.util.concurrent.Executor es)
      Create an IdleManager.
    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      private static java.lang.String folderName​(Folder folder)
      Return the fully qualified name of the folder, for use in log messages.
      boolean isRunning()
      Is the IdleManager currently running? The IdleManager starts running when the Executor schedules its task.
      private void processKeys()
      Process the selected keys.
      (package private) void requestAbort​(IMAPFolder folder)
      Request that the specified folder abort an IDLE command.
      private void select()
      Run the select loop to poll each watched folder for events sent from the server.
      void stop()
      Stop the IdleManager.
      private void unwatchAll()
      Stop watching all folders.
      void watch​(Folder folder)
      Watch the Folder for new messages and other events using the IMAP IDLE command.
      private void watchAll()
      Register all of the folders in the queue with the selector, switching them to nonblocking I/O mode first.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • es

        private java.util.concurrent.Executor es
      • selector

        private java.nio.channels.Selector selector
      • die

        private volatile boolean die
      • running

        private volatile boolean running
      • toWatch

        private java.util.Queue<IMAPFolder> toWatch
      • toAbort

        private java.util.Queue<IMAPFolder> toAbort
    • Constructor Detail

      • IdleManager

        public IdleManager​(Session session,
                           java.util.concurrent.Executor es)
                    throws java.io.IOException
        Create an IdleManager. The Session is used only to configure debugging output. The Executor is used to create the "select" thread.
        Parameters:
        session - the Session containing configuration information
        es - the Executor used to create threads
        Throws:
        java.io.IOException - for Selector failures
    • Method Detail

      • isRunning

        public boolean isRunning()
        Is the IdleManager currently running? The IdleManager starts running when the Executor schedules its task. The IdleManager stops running after its task detects the stop request from the stop method, or if it terminates abnormally due to an unexpected error.
        Returns:
        true if the IdleMaanger is running
        Since:
        JavaMail 1.5.5
      • watch

        public void watch​(Folder folder)
                   throws MessagingException
        Watch the Folder for new messages and other events using the IMAP IDLE command.
        Parameters:
        folder - the folder to watch
        Throws:
        MessagingException - for errors related to the folder
      • requestAbort

        void requestAbort​(IMAPFolder folder)
        Request that the specified folder abort an IDLE command. We can't do the abort directly because the DONE message needs to be sent through the (potentially) SSL socket, which means we need to be in blocking I/O mode. We can only switch to blocking I/O mode when not selecting, so wake up the selector, which will process this request when it wakes up.
      • select

        private void select()
        Run the select loop to poll each watched folder for events sent from the server.
      • watchAll

        private void watchAll()
        Register all of the folders in the queue with the selector, switching them to nonblocking I/O mode first.
      • processKeys

        private void processKeys()
                          throws java.io.IOException
        Process the selected keys.
        Throws:
        java.io.IOException
      • unwatchAll

        private void unwatchAll()
        Stop watching all folders. Cancel any selection keys and, most importantly, switch the channel back to blocking mode. If there's any folders waiting to be watched, need to abort them too.
      • stop

        public void stop()
        Stop the IdleManager. The IdleManager can not be restarted.
      • folderName

        private static java.lang.String folderName​(Folder folder)
        Return the fully qualified name of the folder, for use in log messages. Essentially just the getURLName method, but ignoring the MessagingException that can never happen.