Interface ChannelGroupFuture
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- All Superinterfaces:
Iterable<ChannelFuture>
- All Known Implementing Classes:
DefaultChannelGroupFuture
public interface ChannelGroupFuture extends Iterable<ChannelFuture>
The result of an asynchronousChannelGroup
operation.ChannelGroupFuture
is composed ofChannelFuture
s which represent the outcome of the individual I/O operations that affect theChannel
s in theChannelGroup
.All I/O operations in
ChannelGroup
are asynchronous. It means any I/O calls will return immediately with no guarantee that the requested I/O operations have been completed at the end of the call. Instead, you will be returned with aChannelGroupFuture
instance which tells you when the requested I/O operations have succeeded, failed, or cancelled.Various methods are provided to let you check if the I/O operations has been completed, wait for the completion, and retrieve the result of the I/O operation. It also allows you to add more than one
ChannelGroupFutureListener
so you can get notified when the I/O operation have been completed.Prefer
It is recommended to preferaddListener(ChannelGroupFutureListener)
toawait()
addListener(ChannelGroupFutureListener)
toawait()
wherever possible to get notified when I/O operations are done and to do any follow-up tasks.addListener(ChannelGroupFutureListener)
is non-blocking. It simply adds the specifiedChannelGroupFutureListener
to theChannelGroupFuture
, and I/O thread will notify the listeners when the I/O operations associated with the future is done.ChannelGroupFutureListener
yields the best performance and resource utilization because it does not block at all, but it could be tricky to implement a sequential logic if you are not used to event-driven programming.By contrast,
await()
is a blocking operation. Once called, the caller thread blocks until all I/O operations are done. It is easier to implement a sequential logic withawait()
, but the caller thread blocks unnecessarily until all I/O operations are done and there's relatively expensive cost of inter-thread notification. Moreover, there's a chance of dead lock in a particular circumstance, which is described below.Do not call
await()
insideChannelHandler
The event handler methods in
ChannelHandler
is often called by an I/O thread unless anExecutionHandler
is in theChannelPipeline
. Ifawait()
is called by an event handler method, which is called by the I/O thread, the I/O operation it is waiting for might never be complete becauseawait()
can block the I/O operation it is waiting for, which is a dead lock.// BAD - NEVER DO THIS
@Override
public void messageReceived(ChannelHandlerContext
ctx,MessageEvent
e) { if (e.getMessage() instanceof ShutdownMessage) {ChannelGroup
allChannels = MyServer.getAllChannels();ChannelGroupFuture
future = allChannels.close(); future.awaitUninterruptibly(); // Perform post-shutdown operation // ... } } // GOOD@Override
public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) { if (e.getMessage() instanceof ShutdownMessage) {ChannelGroup
allChannels = MyServer.getAllChannels();ChannelGroupFuture
future = allChannels.close(); future.addListener(newChannelGroupFutureListener
() { public void operationComplete(ChannelGroupFuture
future) { // Perform post-closure operation // ... } }); } }In spite of the disadvantages mentioned above, there are certainly the cases where it is more convenient to call
await()
. In such a case, please make sure you do not callawait()
in an I/O thread. Otherwise,IllegalStateException
will be raised to prevent a dead lock.
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description void
addListener(ChannelGroupFutureListener listener)
Adds the specified listener to this future.ChannelGroupFuture
await()
Waits for this future to be completed.boolean
await(long timeoutMillis)
Waits for this future to be completed within the specified time limit.boolean
await(long timeout, TimeUnit unit)
Waits for this future to be completed within the specified time limit.ChannelGroupFuture
awaitUninterruptibly()
Waits for this future to be completed without interruption.boolean
awaitUninterruptibly(long timeoutMillis)
Waits for this future to be completed within the specified time limit without interruption.boolean
awaitUninterruptibly(long timeout, TimeUnit unit)
Waits for this future to be completed within the specified time limit without interruption.ChannelFuture
find(Integer channelId)
Returns theChannelFuture
of the individual I/O operation which is associated with theChannel
whose ID matches the specified integer.ChannelFuture
find(Channel channel)
Returns theChannelFuture
of the individual I/O operation which is associated with the specifiedChannel
.ChannelGroup
getGroup()
Returns theChannelGroup
which is associated with this future.boolean
isCompleteFailure()
Returnstrue
if and only if all I/O operations associated with this future have failed without any success.boolean
isCompleteSuccess()
Returnstrue
if and only if all I/O operations associated with this future were successful without any failure.boolean
isDone()
Returnstrue
if and only if this future is complete, regardless of whether the operation was successful, failed, or canceled.boolean
isPartialFailure()
Returnstrue
if and only if the I/O operations associated with this future have failed partially with some success.boolean
isPartialSuccess()
Returnstrue
if and only if the I/O operations associated with this future were partially successful with some failure.Iterator<ChannelFuture>
iterator()
Returns theIterator
that enumerates allChannelFuture
s which are associated with this future.void
removeListener(ChannelGroupFutureListener listener)
Removes the specified listener from this future.-
Methods inherited from interface java.lang.Iterable
forEach, spliterator
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Method Detail
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getGroup
ChannelGroup getGroup()
Returns theChannelGroup
which is associated with this future.
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find
ChannelFuture find(Integer channelId)
Returns theChannelFuture
of the individual I/O operation which is associated with theChannel
whose ID matches the specified integer.- Returns:
- the matching
ChannelFuture
if found.null
otherwise.
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find
ChannelFuture find(Channel channel)
Returns theChannelFuture
of the individual I/O operation which is associated with the specifiedChannel
.- Returns:
- the matching
ChannelFuture
if found.null
otherwise.
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isDone
boolean isDone()
Returnstrue
if and only if this future is complete, regardless of whether the operation was successful, failed, or canceled.
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isCompleteSuccess
boolean isCompleteSuccess()
Returnstrue
if and only if all I/O operations associated with this future were successful without any failure.
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isPartialSuccess
boolean isPartialSuccess()
Returnstrue
if and only if the I/O operations associated with this future were partially successful with some failure.
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isCompleteFailure
boolean isCompleteFailure()
Returnstrue
if and only if all I/O operations associated with this future have failed without any success.
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isPartialFailure
boolean isPartialFailure()
Returnstrue
if and only if the I/O operations associated with this future have failed partially with some success.
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addListener
void addListener(ChannelGroupFutureListener listener)
Adds the specified listener to this future. The specified listener is notified when this future is done. If this future is already completed, the specified listener is notified immediately.
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removeListener
void removeListener(ChannelGroupFutureListener listener)
Removes the specified listener from this future. The specified listener is no longer notified when this future is done. If this future is already completed, this method has no effect and returns silently.
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await
ChannelGroupFuture await() throws InterruptedException
Waits for this future to be completed.- Throws:
InterruptedException
- if the current thread was interrupted
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awaitUninterruptibly
ChannelGroupFuture awaitUninterruptibly()
Waits for this future to be completed without interruption. This method catches anInterruptedException
and discards it silently.
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await
boolean await(long timeout, TimeUnit unit) throws InterruptedException
Waits for this future to be completed within the specified time limit.- Returns:
true
if and only if the future was completed within the specified time limit- Throws:
InterruptedException
- if the current thread was interrupted
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await
boolean await(long timeoutMillis) throws InterruptedException
Waits for this future to be completed within the specified time limit.- Returns:
true
if and only if the future was completed within the specified time limit- Throws:
InterruptedException
- if the current thread was interrupted
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awaitUninterruptibly
boolean awaitUninterruptibly(long timeout, TimeUnit unit)
Waits for this future to be completed within the specified time limit without interruption. This method catches anInterruptedException
and discards it silently.- Returns:
true
if and only if the future was completed within the specified time limit
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awaitUninterruptibly
boolean awaitUninterruptibly(long timeoutMillis)
Waits for this future to be completed within the specified time limit without interruption. This method catches anInterruptedException
and discards it silently.- Returns:
true
if and only if the future was completed within the specified time limit
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iterator
Iterator<ChannelFuture> iterator()
Returns theIterator
that enumerates allChannelFuture
s which are associated with this future. Please note that the returnedIterator
is is unmodifiable, which means aChannelFuture
cannot be removed from this future.- Specified by:
iterator
in interfaceIterable<ChannelFuture>
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