ChannelGroupFuture (Netty API Reference (4.1.115.Final))

All Superinterfaces:

Future<Void>, Iterable<ChannelFuture>
```
public interface ChannelGroupFuture
extends Future<Void>, Iterable<ChannelFuture>
```
The result of an asynchronous ChannelGroup operation. ChannelGroupFuture is composed of ChannelFutures which represent the outcome of the individual I/O operations that affect the Channels in the ChannelGroup.
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 a ChannelGroupFuture 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 addListener(GenericFutureListener) to await()
It is recommended to prefer addListener(GenericFutureListener) to await() wherever possible to get notified when I/O operations are done and to do any follow-up tasks.
addListener(GenericFutureListener) is non-blocking. It simply adds the specified ChannelGroupFutureListener to the ChannelGroupFuture, 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 with await(), 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() inside ChannelHandler

The event handler methods in ChannelHandler is often called by an I/O thread. If await() 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 because await() 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, ShutdownMessage msg) {
     ChannelGroup allChannels = MyServer.getAllChannels();
     ChannelGroupFuture future = allChannels.close();
     future.awaitUninterruptibly();
     // Perform post-shutdown operation
     // ...

 }

 // GOOD
  @Override
 public void messageReceived(ChannelHandlerContext ctx, ShutdownMessage msg) {
     ChannelGroup allChannels = MyServer.getAllChannels();
     ChannelGroupFuture future = allChannels.close();
     future.addListener(new ChannelGroupFutureListener() {
         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 call await() in an I/O thread. Otherwise, IllegalStateException will be raised to prevent a dead lock.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`ChannelGroupFuture`	`addListener(GenericFutureListener<? extends Future<? super Void>> listener)` Adds the specified listener to this future.
`ChannelGroupFuture`	`addListeners(GenericFutureListener<? extends Future<? super Void>>... listeners)` Adds the specified listeners to this future.
`ChannelGroupFuture`	`await()` Waits for this future to be completed.
`ChannelGroupFuture`	`awaitUninterruptibly()` Waits for this future to be completed without interruption.
`ChannelGroupException`	`cause()` Returns the cause of the failed I/O operation if the I/O operation has failed.
`ChannelFuture`	`find(Channel channel)` Returns the `ChannelFuture` of the individual I/O operation which is associated with the specified `Channel`.
`ChannelGroup`	`group()` Returns the `ChannelGroup` which is associated with this future.
`boolean`	`isPartialFailure()` Returns `true` if and only if the I/O operations associated with this future have failed partially with some success.
`boolean`	`isPartialSuccess()` Returns `true` if and only if the I/O operations associated with this future were partially successful with some failure.
`boolean`	`isSuccess()` Returns `true` if and only if all I/O operations associated with this future were successful without any failure.
`Iterator<ChannelFuture>`	`iterator()` Returns the `Iterator` that enumerates all `ChannelFuture`s which are associated with this future.
`ChannelGroupFuture`	`removeListener(GenericFutureListener<? extends Future<? super Void>> listener)` Removes the first occurrence of the specified listener from this future.
`ChannelGroupFuture`	`removeListeners(GenericFutureListener<? extends Future<? super Void>>... listeners)` Removes the first occurrence for each of the listeners from this future.
`ChannelGroupFuture`	`sync()` Waits for this future until it is done, and rethrows the cause of the failure if this future failed.
`ChannelGroupFuture`	`syncUninterruptibly()` Waits for this future until it is done, and rethrows the cause of the failure if this future failed.

Methods inherited from interface io.netty.util.concurrent.Future
await, await, awaitUninterruptibly, awaitUninterruptibly, cancel, getNow, isCancellable

Methods inherited from interface java.util.concurrent.Future
get, get, isCancelled, isDone

Methods inherited from interface java.lang.Iterable
forEach, spliterator

- Method Detail
  - group
```
ChannelGroup group()
```
    Returns the ChannelGroup which is associated with this future.
  - find
```
ChannelFuture find(Channel channel)
```
    Returns the ChannelFuture of the individual I/O operation which is associated with the specified Channel.
    
    Returns:
    
    the matching ChannelFuture if found. null otherwise.
  - isSuccess
```
boolean isSuccess()
```
    Returns true if and only if all I/O operations associated with this future were successful without any failure.
  - cause
```
ChannelGroupException cause()
```
    Description copied from interface: Future
    
    Returns the cause of the failed I/O operation if the I/O operation has failed.
    
    Returns:
    
    the cause of the failure. null if succeeded or this future is not completed yet.
  - isPartialSuccess
```
boolean isPartialSuccess()
```
    Returns true if and only if the I/O operations associated with this future were partially successful with some failure.
  - isPartialFailure
```
boolean isPartialFailure()
```
    Returns true if and only if the I/O operations associated with this future have failed partially with some success.
  - addListener
```
ChannelGroupFuture addListener(GenericFutureListener<? extends Future<? super Void>> listener)
```
    Description copied from interface: Future
    
    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.
  - addListeners
```
ChannelGroupFuture addListeners(GenericFutureListener<? extends Future<? super Void>>... listeners)
```
    Description copied from interface: Future
    
    Adds the specified listeners to this future. The specified listeners are notified when this future is done. If this future is already completed, the specified listeners are notified immediately.
  - removeListener
```
ChannelGroupFuture removeListener(GenericFutureListener<? extends Future<? super Void>> listener)
```
    Description copied from interface: Future
    
    Removes the first occurrence of the specified listener from this future. The specified listener is no longer notified when this future is done. If the specified listener is not associated with this future, this method does nothing and returns silently.
  - removeListeners
```
ChannelGroupFuture removeListeners(GenericFutureListener<? extends Future<? super Void>>... listeners)
```
    Description copied from interface: Future
    
    Removes the first occurrence for each of the listeners from this future. The specified listeners are no longer notified when this future is done. If the specified listeners are not associated with this future, this method does nothing and returns silently.
  - await
```
ChannelGroupFuture await()
                  throws InterruptedException
```
    Description copied from interface: Future
    
    Waits for this future to be completed.
    
    Throws:
    
    InterruptedException - if the current thread was interrupted
  - awaitUninterruptibly
```
ChannelGroupFuture awaitUninterruptibly()
```
    Description copied from interface: Future
    
    Waits for this future to be completed without interruption. This method catches an InterruptedException and discards it silently.
  - syncUninterruptibly
```
ChannelGroupFuture syncUninterruptibly()
```
    Description copied from interface: Future
    
    Waits for this future until it is done, and rethrows the cause of the failure if this future failed.
  - sync
```
ChannelGroupFuture sync()
                 throws InterruptedException
```
    Description copied from interface: Future
    
    Waits for this future until it is done, and rethrows the cause of the failure if this future failed.
    
    Throws:
    
    InterruptedException
  - iterator
```
Iterator<ChannelFuture> iterator()
```
    Returns the Iterator that enumerates all ChannelFutures which are associated with this future. Please note that the returned Iterator is unmodifiable, which means a ChannelFuture cannot be removed from this future.
    
    Specified by:
    
    iterator in interface Iterable<ChannelFuture>

Interface ChannelGroupFuture

Prefer `addListener(GenericFutureListener)` to `await()`

Do not call `await()` inside `ChannelHandler`

Method Summary

Methods inherited from interface io.netty.util.concurrent.Future

Methods inherited from interface java.util.concurrent.Future

Methods inherited from interface java.lang.Iterable

Method Detail

group

find

isSuccess

cause

isPartialSuccess

isPartialFailure

addListener

addListeners

removeListener

removeListeners

await

awaitUninterruptibly

syncUninterruptibly

sync

iterator

Interface ChannelGroupFuture

Prefer addListener(GenericFutureListener) to await()

Do not call await() inside ChannelHandler

Method Summary

Methods inherited from interface io.netty.util.concurrent.Future

Methods inherited from interface java.util.concurrent.Future

Methods inherited from interface java.lang.Iterable

Method Detail

group

find

isSuccess

cause

isPartialSuccess

isPartialFailure

addListener

addListeners

removeListener

removeListeners

await

awaitUninterruptibly

syncUninterruptibly

sync

iterator

Prefer `addListener(GenericFutureListener)` to `await()`

Do not call `await()` inside `ChannelHandler`