我正在制作一个需要监控Gmail帐户以查找新邮件的程序,为了尽快获取它们,我正在使用JavaMail的空闲功能。这是我用来调用folder.idle()的线程的代码片段:
//Run method that waits for idle input. If an exception occurs, end the thread's life.
public void run() {
IMAPFolder folder = null;
try {
folder = getFolder();
while(true)
{
//If connection has been lost, attempt to restore it
if (!folder.isOpen())
folder = getFolder();
//Wait until something happens in inbox
folder.idle(true);
//Notify controller of event
cont.inboxEventOccured();
}
}
catch (Exception ex) {
ex.printStackTrace();
}
System.out.println("MailIdleWaiter thread ending.");
}
getFolder()方法基本上打开与IMAP服务器的连接并打开收件箱。
这种方法有一段时间了,但是大约10分钟后它就会停止更新(不会抛出任何异常)。
我正在寻找保持连接活着的建议。我是否需要第二个线程,其唯一的作用是每10分钟睡眠并更新idle()线程,还是有更容易/更好的方法?
提前致谢。
答案 0 :(得分:22)
一个常见的错误是假设IDLE命令将无限期地发布更新。但是,定义IDLE扩展名的RFC 2177表示:
特别是GMail,如你所说,大约10分钟就会超时。如果客户端具有IDLE命令,则可以认为客户端处于非活动状态 运行,如果这样的服务器有一个不活动超时,它可能会记录 客户端在超时期限结束时隐式关闭。因为 其中,建议使用IDLE的客户端终止IDLE和 至少每29分钟重新发一次,以免被注销。 这仍然允许客户端甚至接收即时邮箱更新 虽然它只需要半小时的“轮询”。
我们只需每9分钟左右重新发出一次IDLE命令即可运行。 javax.mail
API无法为IDLE命令设置超时,因此您需要第二个线程来移动它。
第一种方法是让第二个线程中断第一个线程,处理异常并忽略它。然而,这将允许没有干净的方式来关闭线程,所以我不会推荐它。更简洁的方法是让第二个线程向服务器发出NOOP命令。这根本不做什么,但足以让IDLE中止并重新发布。
我在这里提供了一些代码来执行此操作:
public void startListening(IMAPFolder imapFolder) {
// We need to create a new thread to keep alive the connection
Thread t = new Thread(
new KeepAliveRunnable(imapFolder), "IdleConnectionKeepAlive"
);
t.start();
while (!Thread.interrupted()) {
LOGGER.debug("Starting IDLE");
try {
imapFolder.idle();
} catch (MessagingException e) {
LOGGER.warn("Messaging exception during IDLE", e);
throw new RuntimeException(e);
}
}
// Shutdown keep alive thread
if (t.isAlive()) {
t.interrupt();
}
}
/**
* Runnable used to keep alive the connection to the IMAP server
*
* @author Juan Martín Sotuyo Dodero <jmsotuyo@monits.com>
*/
private static class KeepAliveRunnable implements Runnable {
private static final long KEEP_ALIVE_FREQ = 300000; // 5 minutes
private IMAPFolder folder;
public KeepAliveRunnable(IMAPFolder folder) {
this.folder = folder;
}
@Override
public void run() {
while (!Thread.interrupted()) {
try {
Thread.sleep(KEEP_ALIVE_FREQ);
// Perform a NOOP just to keep alive the connection
LOGGER.debug("Performing a NOOP to keep alvie the connection");
folder.doCommand(new IMAPFolder.ProtocolCommand() {
public Object doCommand(IMAPProtocol p)
throws ProtocolException {
p.simpleCommand("NOOP", null);
return null;
}
});
} catch (InterruptedException e) {
// Ignore, just aborting the thread...
} catch (MessagingException e) {
// Shouldn't really happen...
LOGGER.warn("Unexpected exception while keeping alive the IDLE connection", e);
}
}
}
}
答案 1 :(得分:3)
@ user888307的建议是一个肮脏的黑客,最终惨遭失败。实际上只有一种正确的方法。
在当前选定的文件夹上调用idle(false)方法。理想情况下收件箱,因为它将收到所有邮件。
调用idle(false)将基本上挂起线程的运行时,因此最好将idle(false)放在新线程上。然后,一旦您使用messageCountChange收到新的电子邮件/通知,您必须重新运行此线程。
这是实现这一目标的唯一真正方法。当我编写一个名为JavaPushMail的程序时,我已经为你的显式问题写了一个包装器。您可以在我的网站上找到更多信息(http://www.mofirouz.com/wordpress),或者您可以在GitHub https://github.com/mofirouz/JavaPushMail上抓取应用程序(目前正在开发中)
答案 2 :(得分:3)
实际上Java Mail samples包含IMAP IDLE示例,如下所示。 除此之外,IdleManager class可能很有趣。
/*
* Copyright (c) 1996-2010 Oracle and/or its affiliates. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Oracle nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import java.util.*;
import java.io.*;
import javax.mail.*;
import javax.mail.event.*;
import javax.activation.*;
import com.sun.mail.imap.*;
/* Monitors given mailbox for new mail */
public class monitor {
public static void main(String argv[]) {
if (argv.length != 5) {
System.out.println(
"Usage: monitor <host> <user> <password> <mbox> <freq>");
System.exit(1);
}
System.out.println("\nTesting monitor\n");
try {
Properties props = System.getProperties();
// Get a Session object
Session session = Session.getInstance(props, null);
// session.setDebug(true);
// Get a Store object
Store store = session.getStore("imap");
// Connect
store.connect(argv[0], argv[1], argv[2]);
// Open a Folder
Folder folder = store.getFolder(argv[3]);
if (folder == null || !folder.exists()) {
System.out.println("Invalid folder");
System.exit(1);
}
folder.open(Folder.READ_WRITE);
// Add messageCountListener to listen for new messages
folder.addMessageCountListener(new MessageCountAdapter() {
public void messagesAdded(MessageCountEvent ev) {
Message[] msgs = ev.getMessages();
System.out.println("Got " + msgs.length + " new messages");
// Just dump out the new messages
for (int i = 0; i < msgs.length; i++) {
try {
System.out.println("-----");
System.out.println("Message " +
msgs[i].getMessageNumber() + ":");
msgs[i].writeTo(System.out);
} catch (IOException ioex) {
ioex.printStackTrace();
} catch (MessagingException mex) {
mex.printStackTrace();
}
}
}
});
// Check mail once in "freq" MILLIseconds
int freq = Integer.parseInt(argv[4]);
boolean supportsIdle = false;
try {
if (folder instanceof IMAPFolder) {
IMAPFolder f = (IMAPFolder)folder;
f.idle();
supportsIdle = true;
}
} catch (FolderClosedException fex) {
throw fex;
} catch (MessagingException mex) {
supportsIdle = false;
}
for (;;) {
if (supportsIdle && folder instanceof IMAPFolder) {
IMAPFolder f = (IMAPFolder)folder;
f.idle();
System.out.println("IDLE done");
} else {
Thread.sleep(freq); // sleep for freq milliseconds
// This is to force the IMAP server to send us
// EXISTS notifications.
folder.getMessageCount();
}
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
答案 3 :(得分:1)
您可以将文件夹注册到 connectionListener
。
var folder = store.getFolder("<FOLDER_NAME>");
folder.addConnectionListener(new javax.mail.event ConnectionAdapter() {
public void closed(ConnectionEvent e) {
try {
log.info("Folder connection closed. Reconnect to server");
// reopen connection
connectToServer();
} catch (Exception exception) {
log.error("Could not connect to server={0}", exception);
}
}
});
答案 4 :(得分:-6)
new Thread()
{
@Override
public void run()
{
startTimer();
}
private void startTimer()
{
int seconds = 0;
while (true)
{
try
{
Thread.sleep(300000);
int c = folder.getMessageCount();
}
catch (InterruptedException ex)
{
}
catch (MessagingException me)
{
}
}
}
}.start();