com.sun.mail.imap.IdleManager Maven / Gradle / Ivy
/*
* Copyright (c) 2014, 2018 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package com.sun.mail.imap;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.net.Socket;
import java.nio.*;
import java.nio.channels.*;
import java.util.*;
import java.util.logging.*;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.Executor;
import javax.mail.*;
import com.sun.mail.imap.protocol.IMAPProtocol;
import com.sun.mail.util.MailLogger;
/**
* 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:
*
* {@literal @}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
* {@link java.nio.channels.SocketChannel SocketChannel} must be used instead
* of a {@link java.net.Socket 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
* {@link com.sun.mail.imap.IMAPFolder#idle 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
*/
public class IdleManager {
private Executor es;
private Selector selector;
private MailLogger logger;
private volatile boolean die = false;
private volatile boolean running;
private Queue toWatch = new ConcurrentLinkedQueue<>();
private Queue toAbort = new ConcurrentLinkedQueue<>();
/**
* Create an IdleManager. The Session is used only to configure
* debugging output. The Executor is used to create the
* "select" thread.
*
* @param session the Session containing configuration information
* @param es the Executor used to create threads
* @exception IOException for Selector failures
*/
public IdleManager(Session session, Executor es) throws IOException {
this.es = es;
logger = new MailLogger(this.getClass(), "DEBUG IMAP",
session.getDebug(), session.getDebugOut());
selector = Selector.open();
es.execute(new Runnable() {
@Override
public void run() {
logger.fine("IdleManager select starting");
try {
running = true;
select();
} finally {
running = false;
logger.fine("IdleManager select terminating");
}
}
});
}
/**
* 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
* {@link #stop stop} method, or if it terminates abnormally due
* to an unexpected error.
*
* @return true if the IdleMaanger is running
* @since JavaMail 1.5.5
*/
public boolean isRunning() {
return running;
}
/**
* Watch the Folder for new messages and other events using the IMAP IDLE
* command.
*
* @param folder the folder to watch
* @exception MessagingException for errors related to the folder
*/
public void watch(Folder folder)
throws MessagingException {
if (die) // XXX - should be IllegalStateException?
throw new MessagingException("IdleManager is not running");
if (!(folder instanceof IMAPFolder))
throw new MessagingException("Can only watch IMAP folders");
IMAPFolder ifolder = (IMAPFolder)folder;
SocketChannel sc = ifolder.getChannel();
if (sc == null) {
if (folder.isOpen())
throw new MessagingException(
"Folder is not using SocketChannels");
else
throw new MessagingException("Folder is not open");
}
if (logger.isLoggable(Level.FINEST))
logger.log(Level.FINEST, "IdleManager watching {0}",
folderName(ifolder));
// keep trying to start the IDLE command until we're successful.
// may block if we're in the middle of aborting an IDLE command.
int tries = 0;
while (!ifolder.startIdle(this)) {
if (logger.isLoggable(Level.FINEST))
logger.log(Level.FINEST,
"IdleManager.watch startIdle failed for {0}",
folderName(ifolder));
tries++;
}
if (logger.isLoggable(Level.FINEST)) {
if (tries > 0)
logger.log(Level.FINEST,
"IdleManager.watch startIdle succeeded for {0}" +
" after " + tries + " tries",
folderName(ifolder));
else
logger.log(Level.FINEST,
"IdleManager.watch startIdle succeeded for {0}",
folderName(ifolder));
}
synchronized (this) {
toWatch.add(ifolder);
selector.wakeup();
}
}
/**
* 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.
*/
void requestAbort(IMAPFolder folder) {
toAbort.add(folder);
selector.wakeup();
}
/**
* Run the {@link java.nio.channels.Selector#select select} loop
* to poll each watched folder for events sent from the server.
*/
private void select() {
die = false;
try {
while (!die) {
watchAll();
logger.finest("IdleManager waiting...");
int ns = selector.select();
if (logger.isLoggable(Level.FINEST))
logger.log(Level.FINEST,
"IdleManager selected {0} channels", ns);
if (die || Thread.currentThread().isInterrupted())
break;
/*
* Process any selected folders. We cancel the
* selection key for any selected folder, so if we
* need to continue watching that folder it's added
* to the toWatch list again. We can't actually
* register that folder again until the previous
* selection key is cancelled, so we call selectNow()
* just for the side effect of cancelling the selection
* keys. But if selectNow() selects something, we
* process it before adding folders from the toWatch
* queue. And so on until there is nothing to do, at
* which point it's safe to register folders from the
* toWatch queue. This should be "fair" since each
* selection key is used only once before being added
* to the toWatch list.
*/
do {
processKeys();
} while (selector.selectNow() > 0 || !toAbort.isEmpty());
}
} catch (InterruptedIOException ex) {
logger.log(Level.FINEST, "IdleManager interrupted", ex);
} catch (IOException ex) {
logger.log(Level.FINEST, "IdleManager got I/O exception", ex);
} catch (Exception ex) {
logger.log(Level.FINEST, "IdleManager got exception", ex);
} finally {
die = true; // prevent new watches in case of exception
logger.finest("IdleManager unwatchAll");
try {
unwatchAll();
selector.close();
} catch (IOException ex2) {
// nothing to do...
logger.log(Level.FINEST, "IdleManager unwatch exception", ex2);
}
logger.fine("IdleManager exiting");
}
}
/**
* Register all of the folders in the queue with the selector,
* switching them to nonblocking I/O mode first.
*/
private void watchAll() {
/*
* Pull each of the folders from the toWatch queue
* and register it.
*/
IMAPFolder folder;
while ((folder = toWatch.poll()) != null) {
if (logger.isLoggable(Level.FINEST))
logger.log(Level.FINEST,
"IdleManager adding {0} to selector", folderName(folder));
try {
SocketChannel sc = folder.getChannel();
if (sc == null)
continue;
// has to be non-blocking to select
sc.configureBlocking(false);
sc.register(selector, SelectionKey.OP_READ, folder);
} catch (IOException ex) {
// oh well, nothing to do
logger.log(Level.FINEST,
"IdleManager can't register folder", ex);
} catch (CancelledKeyException ex) {
// this should never happen
logger.log(Level.FINEST,
"IdleManager can't register folder", ex);
}
}
}
/**
* Process the selected keys.
*/
private void processKeys() throws IOException {
IMAPFolder folder;
/*
* First, process any channels with data to read.
*/
Set selectedKeys = selector.selectedKeys();
/*
* XXX - this is simpler, but it can fail with
* ConcurrentModificationException
*
for (SelectionKey sk : selectedKeys) {
selectedKeys.remove(sk); // only process each key once
...
}
*/
Iterator it = selectedKeys.iterator();
while (it.hasNext()) {
SelectionKey sk = it.next();
it.remove(); // only process each key once
// have to cancel so we can switch back to blocking I/O mode
sk.cancel();
folder = (IMAPFolder)sk.attachment();
if (logger.isLoggable(Level.FINEST))
logger.log(Level.FINEST,
"IdleManager selected folder: {0}", folderName(folder));
SelectableChannel sc = sk.channel();
// switch back to blocking to allow normal I/O
sc.configureBlocking(true);
try {
if (folder.handleIdle(false)) {
if (logger.isLoggable(Level.FINEST))
logger.log(Level.FINEST,
"IdleManager continue watching folder {0}",
folderName(folder));
// more to do with this folder, select on it again
toWatch.add(folder);
} else {
// done watching this folder,
if (logger.isLoggable(Level.FINEST))
logger.log(Level.FINEST,
"IdleManager done watching folder {0}",
folderName(folder));
}
} catch (MessagingException ex) {
// something went wrong, stop watching this folder
logger.log(Level.FINEST,
"IdleManager got exception for folder: " +
folderName(folder), ex);
}
}
/*
* Now, process any folders that we need to abort.
*/
while ((folder = toAbort.poll()) != null) {
if (logger.isLoggable(Level.FINEST))
logger.log(Level.FINEST,
"IdleManager aborting IDLE for folder: {0}",
folderName(folder));
SocketChannel sc = folder.getChannel();
if (sc == null)
continue;
SelectionKey sk = sc.keyFor(selector);
// have to cancel so we can switch back to blocking I/O mode
if (sk != null)
sk.cancel();
// switch back to blocking to allow normal I/O
sc.configureBlocking(true);
// if there's a read timeout, have to do the abort in a new thread
Socket sock = sc.socket();
if (sock != null && sock.getSoTimeout() > 0) {
logger.finest("IdleManager requesting DONE with timeout");
toWatch.remove(folder);
final IMAPFolder folder0 = folder;
es.execute(new Runnable() {
@Override
public void run() {
// send the DONE and wait for the response
folder0.idleAbortWait();
}
});
} else {
folder.idleAbort(); // send the DONE message
// watch for OK response to DONE
// XXX - what if we also added it above? should be a nop
toWatch.add(folder);
}
}
}
/**
* 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.
*/
private void unwatchAll() {
IMAPFolder folder;
Set keys = selector.keys();
for (SelectionKey sk : keys) {
// have to cancel so we can switch back to blocking I/O mode
sk.cancel();
folder = (IMAPFolder)sk.attachment();
if (logger.isLoggable(Level.FINEST))
logger.log(Level.FINEST,
"IdleManager no longer watching folder: {0}",
folderName(folder));
SelectableChannel sc = sk.channel();
// switch back to blocking to allow normal I/O
try {
sc.configureBlocking(true);
folder.idleAbortWait(); // send the DONE message and wait
} catch (IOException ex) {
// ignore it, channel might be closed
logger.log(Level.FINEST,
"IdleManager exception while aborting idle for folder: " +
folderName(folder), ex);
}
}
/*
* Finally, process any folders waiting to be watched.
*/
while ((folder = toWatch.poll()) != null) {
if (logger.isLoggable(Level.FINEST))
logger.log(Level.FINEST,
"IdleManager aborting IDLE for unwatched folder: {0}",
folderName(folder));
SocketChannel sc = folder.getChannel();
if (sc == null)
continue;
try {
// channel should still be in blocking mode, but make sure
sc.configureBlocking(true);
folder.idleAbortWait(); // send the DONE message and wait
} catch (IOException ex) {
// ignore it, channel might be closed
logger.log(Level.FINEST,
"IdleManager exception while aborting idle for folder: " +
folderName(folder), ex);
}
}
}
/**
* Stop the IdleManager. The IdleManager can not be restarted.
*/
public synchronized void stop() {
die = true;
logger.fine("IdleManager stopping");
selector.wakeup();
}
/**
* 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.
*/
private static String folderName(Folder folder) {
try {
return folder.getURLName().toString();
} catch (MessagingException mex) {
// can't happen
return folder.getStore().toString() + "/" + folder.toString();
}
}
}