javamail idle stops triggering messagesAdded after a while,线程锁定
javamail idle stops triggering messagesAdded after a while, thread locked
我正在开发一个 android 应用程序来接收和处理邮件消息。该应用程序必须连接到 IMAP 服务器并保持连接有效，以便它可以立即查看和处理新邮件消息（邮件包含来自邮件 api 服务器的 json 数据）。该应用程序有两种模式，手动和实时连接。这是我的一些代码：
class Idler {
Thread th;
volatile Boolean isIdling=false;
boolean shouldsync=false;//we need to see if we have unseen mails
Object idleLock;
Handler handler=new Handler();
IMAPFolder inbox;
public boolean keppAliveConnection;//keep alive connection, or manual mode
//This thread should keep the idle connection alive, or in case it's set to manual mode (keppAliveConnection=false) get new mail.
Thread refreshThread;
synchronized void refresh()
{
if(isIdling)//if already idling, just keep connection alive
{
refreshThread =new Thread(new Runnable() {
@Override
public void run() {
try {
inbox.doCommand(new IMAPFolder.ProtocolCommand() {
@Override
public Object doCommand(IMAPProtocol protocol) throws ProtocolException {
//Why not noop?
//any call to IMAPFolder.doCommand() will trigger waitIfIdle, this
//issues a "DONE" command and waits for idle to return(ideally with a DONE server response).
// So... I think NOOP is unnecessary
//protocol.simpleCommand("NOOP",null); I'm not issuing noop due to what I said ^
//PD: if connection was broken, then server response will never arrive, and idle will keep running forever
//without triggering messagesAdded event any more :'( I see any other explanation to this phenomenon
return null;
}
});
} catch (MessagingException e) {
e.printStackTrace();
}
}
},"SyncThread");
refreshThread.start();
}
else
{
getNewMail();//If manual mode keppAliveConnection=false) get the new mail
}
}
public Idler()
{
th=new Thread(new Runnable() {
@SuppressWarnings("InfiniteLoopStatement")
@Override
public void run() {
while (true)
{
try {
if(refreshThread !=null && refreshThread.isAlive())
refreshThread.interrupt();//if the refresher thread is active: interrupt. I thing this is not necessary at this point, but not shure
initIMAP();//initializes imap store
try {
shouldsync=connectIMAP()||shouldsync;//if was disconnected or ordered to sync: needs to sync
}
catch (Exception e)
{
Thread.sleep(5000);//if can't connect: wait some time and throw
throw e;
}
shouldsync=initInbox()||shouldsync;//if inbox was null or closed: needs to sync
if(shouldsync)//if needs to sync
{
getNewMail();//gets new unseen mail
shouldsync=false;//already refreshed, clear sync "flag"
}
while (keppAliveConnection) {//if sould keep idling "forever"
synchronized (idleLock){}//MessageCountListener may be doing some work... wait for it
isIdling = true; //set isIdling "flag"
handler.removeCallbacksAndMessages(null);//clears refresh scheduled tasks
handler.postDelayed(new Runnable() {
@Override
public void run() {
refresh();
}
},1200000);//Schedule a refresh in 20 minutes
inbox.idle();//start idling
if(refreshThread !=null && refreshThread.isAlive())
refreshThread.interrupt();//if the refresher thread is active: interrupt. I thing this is not necessary at this point, but not shure
handler.removeCallbacksAndMessages(null);//clears refresh scheduled tasks
isIdling=false;//clear isIdling "flag"
if(shouldsync)
break;//if ordered to sync... break. The loop will handle it upstairs.
synchronized (idleLock){}//MessageCountListener may be doing some work... wait for it
}
}
catch (Exception e) {
//if the refresher thread is active: interrupt
//Why interrupt? refresher thread may be waiting for idle to return after "DONE" command, but if folder was closed and throws
//a FolderClosedException, then it could wait forever...., so... interrupt.
if (refreshThread != null && refreshThread.isAlive())
refreshThread.interrupt();
handler.removeCallbacksAndMessages(null);//clears refresh scheduled tasks
}
}
}
},"IdlerThread");
th.start();
}
private synchronized void getNewMail()
{
shouldsync=false;
long uid=getLastSeen();//get last unprocessed mail
SearchTerm searchTerm=new UidTerm(uid,Long.MAX_VALUE);//search from las processed message to the las one.
IMAPSearchOperation so=new IMAPSearchOperation(searchTerm);
try {
so.run();//search new messages
final long[] is=so.uids();//get unprocessed messages count
if (is.length > 0) {//if some...
try {
//there are new messages
IMAPFetchMessagesOperation fop=new IMAPFetchMessagesOperation(is);
fop.run();//fetch new messages
if(fop.messages.length>0)
{
//process fetched messages (internally sets the last seen uid value & delete some...)
processMessages(fop.messages);
}
inbox.expunge();//expunge deleted messages if any
}
catch (Exception e)
{
//Do something
}
}
else
{
//Do something
}
}
catch (Exception e)
{
//Do something
}
}
private synchronized void initIMAP()
{
if(store==null)
{
store=new IMAPStore(mailSession,new URLName("imap",p.IMAPServer,p.IMAPPort,null,p.IMAPUser,p.IMAPPassword));
}
}
private boolean connectIMAP() throws MessagingException {
try {
store.connect(p.IMAPServer, p.IMAPPort, p.IMAPUser, p.IMAPPassword);
return true;
}
catch (IllegalStateException e)
{
return false;
}
}
//returns true if the folder was closed or null
private synchronized boolean initInbox() throws MessagingException {
boolean retVal=false;
if(inbox==null)
{//if null, create. This is called after initializing store
inbox = (IMAPFolder) store.getFolder("INBOX");
inbox.addMessageCountListener(countListener);
retVal=true;//was created
}
if(!inbox.isOpen())
{
inbox.open(Folder.READ_WRITE);
retVal=true;//was oppened
}
return retVal;
}
private MessageCountListener countListener= new MessageCountAdapter() {
@Override
public void messagesAdded(MessageCountEvent ev) {
synchronized (idleLock)
{
try {
processMessages(ev.getMessages());//process the new messages, (internally sets the last seen uid value & delete some...)
inbox.expunge();//expunge deleted messajes if any
} catch (MessagingException e) {
//Do something
}
}
}
};
}
问题是：有时，当用户刷新或应用程序自动刷新时，在实时连接模式下，这两种情况中的一种或两种都会使我的应用程序无法接收新消息。这是来自javamail源代码。
1: IdlerThread 进入监听状态:
//I don't know why sometimes it enters monitor state here.
private synchronized void throwClosedException(ConnectionException cex)
throws FolderClosedException, StoreClosedException {
// If it's the folder's protocol object, throw a FolderClosedException;
// otherwise, throw a StoreClosedException.
// If a command has failed because the connection is closed,
// the folder will have already been forced closed by the
// time we get here and our protocol object will have been
// released, so if we no longer have a protocol object we base
// this decision on whether we *think* the folder is open.
if ((protocol != null && cex.getProtocol() == protocol) ||
(protocol == null && !reallyClosed))
throw new FolderClosedException(this, cex.getMessage());
else
throw new StoreClosedException(store, cex.getMessage());
}
2："refresherThread"进入等待状态：
void waitIfIdle() throws ProtocolException {
assert Thread.holdsLock(messageCacheLock);
while (idleState != RUNNING) {
if (idleState == IDLE) {
protocol.idleAbort();
idleState = ABORTING;
}
try {
// give up lock and wait to be not idle
messageCacheLock.wait();//<-----This is the line is driving me crazy.
} catch (InterruptedException ex) { }
}
}
作为这两个线程之一 "stops" 运行（等待和监视状态）我的应用程序在达到此条件时无用。在我的国家，移动数据网络非常不稳定、缓慢且昂贵（GSM）所以它必须具有故障恢复能力并注意每一个传输位。
我想当连接无声地失败并且 refresherThread 开始执行它的工作时就会出现问题。如果 idle 处于活动状态，它会发出 DONE 命令，但是，随着连接断开，当 idle 尝试抛出 FolderClosedException 时，一个或两个线程将被无限期锁定。
所以，我的问题是：为什么会出现这种情况，如何预防呢？我怎样才能安全地保持空闲循环运行而不被锁定？
我试了很多东西，直到筋疲力尽都没有结果。
以下是我阅读过的一些主题，但没有找到解决我的问题的方法。在我的国家/地区，互联网也非常昂贵，因此我无法随心所欲地进行研究，也无法列出我访问过的所有网址来寻找信息。
JavaMail: Keeping IMAPFolder.idle() alive
JavaMail: Keeping IMAPFolder.idle() alive
Javamail : Proper way to issue idle() for IMAPFolder
请原谅我的英语。任何建议将不胜感激。我听说过这个网站的严格性，所以请保持温和，我是新来的。
请务必设置 timeout properties 以确保您不会在等待死连接或服务器时挂起。
您应该调用Folder.isOpen 或Folder.getMessageCount，而不是直接发出nop 命令；如果需要，他们会发出 nop 命令。
如果文件夹被异步关闭 (FolderClosedException)，您将需要重新启动空闲循环。
我正在开发一个 android 应用程序来接收和处理邮件消息。该应用程序必须连接到 IMAP 服务器并保持连接有效，以便它可以立即查看和处理新邮件消息（邮件包含来自邮件 api 服务器的 json 数据）。该应用程序有两种模式，手动和实时连接。这是我的一些代码：
class Idler {
Thread th;
volatile Boolean isIdling=false;
boolean shouldsync=false;//we need to see if we have unseen mails
Object idleLock;
Handler handler=new Handler();
IMAPFolder inbox;
public boolean keppAliveConnection;//keep alive connection, or manual mode
//This thread should keep the idle connection alive, or in case it's set to manual mode (keppAliveConnection=false) get new mail.
Thread refreshThread;
synchronized void refresh()
{
if(isIdling)//if already idling, just keep connection alive
{
refreshThread =new Thread(new Runnable() {
@Override
public void run() {
try {
inbox.doCommand(new IMAPFolder.ProtocolCommand() {
@Override
public Object doCommand(IMAPProtocol protocol) throws ProtocolException {
//Why not noop?
//any call to IMAPFolder.doCommand() will trigger waitIfIdle, this
//issues a "DONE" command and waits for idle to return(ideally with a DONE server response).
// So... I think NOOP is unnecessary
//protocol.simpleCommand("NOOP",null); I'm not issuing noop due to what I said ^
//PD: if connection was broken, then server response will never arrive, and idle will keep running forever
//without triggering messagesAdded event any more :'( I see any other explanation to this phenomenon
return null;
}
});
} catch (MessagingException e) {
e.printStackTrace();
}
}
},"SyncThread");
refreshThread.start();
}
else
{
getNewMail();//If manual mode keppAliveConnection=false) get the new mail
}
}
public Idler()
{
th=new Thread(new Runnable() {
@SuppressWarnings("InfiniteLoopStatement")
@Override
public void run() {
while (true)
{
try {
if(refreshThread !=null && refreshThread.isAlive())
refreshThread.interrupt();//if the refresher thread is active: interrupt. I thing this is not necessary at this point, but not shure
initIMAP();//initializes imap store
try {
shouldsync=connectIMAP()||shouldsync;//if was disconnected or ordered to sync: needs to sync
}
catch (Exception e)
{
Thread.sleep(5000);//if can't connect: wait some time and throw
throw e;
}
shouldsync=initInbox()||shouldsync;//if inbox was null or closed: needs to sync
if(shouldsync)//if needs to sync
{
getNewMail();//gets new unseen mail
shouldsync=false;//already refreshed, clear sync "flag"
}
while (keppAliveConnection) {//if sould keep idling "forever"
synchronized (idleLock){}//MessageCountListener may be doing some work... wait for it
isIdling = true; //set isIdling "flag"
handler.removeCallbacksAndMessages(null);//clears refresh scheduled tasks
handler.postDelayed(new Runnable() {
@Override
public void run() {
refresh();
}
},1200000);//Schedule a refresh in 20 minutes
inbox.idle();//start idling
if(refreshThread !=null && refreshThread.isAlive())
refreshThread.interrupt();//if the refresher thread is active: interrupt. I thing this is not necessary at this point, but not shure
handler.removeCallbacksAndMessages(null);//clears refresh scheduled tasks
isIdling=false;//clear isIdling "flag"
if(shouldsync)
break;//if ordered to sync... break. The loop will handle it upstairs.
synchronized (idleLock){}//MessageCountListener may be doing some work... wait for it
}
}
catch (Exception e) {
//if the refresher thread is active: interrupt
//Why interrupt? refresher thread may be waiting for idle to return after "DONE" command, but if folder was closed and throws
//a FolderClosedException, then it could wait forever...., so... interrupt.
if (refreshThread != null && refreshThread.isAlive())
refreshThread.interrupt();
handler.removeCallbacksAndMessages(null);//clears refresh scheduled tasks
}
}
}
},"IdlerThread");
th.start();
}
private synchronized void getNewMail()
{
shouldsync=false;
long uid=getLastSeen();//get last unprocessed mail
SearchTerm searchTerm=new UidTerm(uid,Long.MAX_VALUE);//search from las processed message to the las one.
IMAPSearchOperation so=new IMAPSearchOperation(searchTerm);
try {
so.run();//search new messages
final long[] is=so.uids();//get unprocessed messages count
if (is.length > 0) {//if some...
try {
//there are new messages
IMAPFetchMessagesOperation fop=new IMAPFetchMessagesOperation(is);
fop.run();//fetch new messages
if(fop.messages.length>0)
{
//process fetched messages (internally sets the last seen uid value & delete some...)
processMessages(fop.messages);
}
inbox.expunge();//expunge deleted messages if any
}
catch (Exception e)
{
//Do something
}
}
else
{
//Do something
}
}
catch (Exception e)
{
//Do something
}
}
private synchronized void initIMAP()
{
if(store==null)
{
store=new IMAPStore(mailSession,new URLName("imap",p.IMAPServer,p.IMAPPort,null,p.IMAPUser,p.IMAPPassword));
}
}
private boolean connectIMAP() throws MessagingException {
try {
store.connect(p.IMAPServer, p.IMAPPort, p.IMAPUser, p.IMAPPassword);
return true;
}
catch (IllegalStateException e)
{
return false;
}
}
//returns true if the folder was closed or null
private synchronized boolean initInbox() throws MessagingException {
boolean retVal=false;
if(inbox==null)
{//if null, create. This is called after initializing store
inbox = (IMAPFolder) store.getFolder("INBOX");
inbox.addMessageCountListener(countListener);
retVal=true;//was created
}
if(!inbox.isOpen())
{
inbox.open(Folder.READ_WRITE);
retVal=true;//was oppened
}
return retVal;
}
private MessageCountListener countListener= new MessageCountAdapter() {
@Override
public void messagesAdded(MessageCountEvent ev) {
synchronized (idleLock)
{
try {
processMessages(ev.getMessages());//process the new messages, (internally sets the last seen uid value & delete some...)
inbox.expunge();//expunge deleted messajes if any
} catch (MessagingException e) {
//Do something
}
}
}
};
}
问题是：有时，当用户刷新或应用程序自动刷新时，在实时连接模式下，这两种情况中的一种或两种都会使我的应用程序无法接收新消息。这是来自javamail源代码。
1: IdlerThread 进入监听状态:
//I don't know why sometimes it enters monitor state here.
private synchronized void throwClosedException(ConnectionException cex)
throws FolderClosedException, StoreClosedException {
// If it's the folder's protocol object, throw a FolderClosedException;
// otherwise, throw a StoreClosedException.
// If a command has failed because the connection is closed,
// the folder will have already been forced closed by the
// time we get here and our protocol object will have been
// released, so if we no longer have a protocol object we base
// this decision on whether we *think* the folder is open.
if ((protocol != null && cex.getProtocol() == protocol) ||
(protocol == null && !reallyClosed))
throw new FolderClosedException(this, cex.getMessage());
else
throw new StoreClosedException(store, cex.getMessage());
}
2："refresherThread"进入等待状态：
void waitIfIdle() throws ProtocolException {
assert Thread.holdsLock(messageCacheLock);
while (idleState != RUNNING) {
if (idleState == IDLE) {
protocol.idleAbort();
idleState = ABORTING;
}
try {
// give up lock and wait to be not idle
messageCacheLock.wait();//<-----This is the line is driving me crazy.
} catch (InterruptedException ex) { }
}
}
作为这两个线程之一 "stops" 运行（等待和监视状态）我的应用程序在达到此条件时无用。在我的国家，移动数据网络非常不稳定、缓慢且昂贵（GSM）所以它必须具有故障恢复能力并注意每一个传输位。
我想当连接无声地失败并且 refresherThread 开始执行它的工作时就会出现问题。如果 idle 处于活动状态，它会发出 DONE 命令，但是，随着连接断开，当 idle 尝试抛出 FolderClosedException 时，一个或两个线程将被无限期锁定。
所以，我的问题是：为什么会出现这种情况，如何预防呢？我怎样才能安全地保持空闲循环运行而不被锁定？
我试了很多东西，直到筋疲力尽都没有结果。
以下是我阅读过的一些主题，但没有找到解决我的问题的方法。在我的国家/地区，互联网也非常昂贵，因此我无法随心所欲地进行研究，也无法列出我访问过的所有网址来寻找信息。
JavaMail: Keeping IMAPFolder.idle() alive
JavaMail: Keeping IMAPFolder.idle() alive
Javamail : Proper way to issue idle() for IMAPFolder
请原谅我的英语。任何建议将不胜感激。我听说过这个网站的严格性，所以请保持温和，我是新来的。
请务必设置 timeout properties 以确保您不会在等待死连接或服务器时挂起。
您应该调用Folder.isOpen 或Folder.getMessageCount，而不是直接发出nop 命令；如果需要，他们会发出 nop 命令。
如果文件夹被异步关闭 (FolderClosedException)，您将需要重新启动空闲循环。