ChannelGroup (Netty API Reference (4.1.115.Final))

All Superinterfaces:: Collection<Channel>, Comparable<ChannelGroup>, Iterable<Channel>, Set<Channel>

All Known Implementing Classes:: DefaultChannelGroup

public interface ChannelGroup
extends Set<Channel>, Comparable<ChannelGroup>

A thread-safe Set that contains open Channels and provides various bulk operations on them. Using ChannelGroup, you can categorize Channels into a meaningful group (e.g. on a per-service or per-state basis.) A closed Channel is automatically removed from the collection, so that you don't need to worry about the life cycle of the added Channel. A Channel can belong to more than one ChannelGroup.

Broadcast a message to multiple `Channel`s

If you need to broadcast a message to more than one Channel, you can add the Channels associated with the recipients and call write(Object):

 ChannelGroup recipients =
         new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
 recipients.add(channelA);
 recipients.add(channelB);
 ..
 recipients.write(Unpooled.copiedBuffer(
         "Service will shut down for maintenance in 5 minutes.",
         CharsetUtil.UTF_8));

Simplify shutdown process with `ChannelGroup`

If both ServerChannels and non-ServerChannels exist in the same ChannelGroup, any requested I/O operations on the group are performed for the ServerChannels first and then for the others.

This rule is very useful when you shut down a server in one shot:

 ChannelGroup allChannels =
         new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

 public static void main(String[] args) throws Exception {
     ServerBootstrap b = new ServerBootstrap(..);
     ...
     b.childHandler(new MyHandler());

     // Start the server
     b.getPipeline().addLast("handler", new MyHandler());
     Channel serverChannel = b.bind(..).sync();
     allChannels.add(serverChannel);

     ... Wait until the shutdown signal reception ...

     // Close the serverChannel and then all accepted connections.
     allChannels.close().awaitUninterruptibly();
 }

 public class MyHandler extends ChannelInboundHandlerAdapter {
      @Override
     public void channelActive(ChannelHandlerContext ctx) {
         // closed on shutdown.
         allChannels.add(ctx.channel());
         super.channelActive(ctx);
     }
 }

Method Summary

All Methods Instance Methods Abstract Methods Deprecated Methods
Modifier and Type	Method and Description
`ChannelGroupFuture`	`close()` Closes all `Channel`s in this group.
`ChannelGroupFuture`	`close(ChannelMatcher matcher)` Closes all `Channel`s in this group that are matched by the given `ChannelMatcher`.
`ChannelGroupFuture`	`deregister()` Deprecated. This method will be removed in the next major feature release. Deregister all `Channel`s in this group from their `EventLoop`. Please note that this operation is asynchronous as `ChannelOutboundInvoker.deregister()` is.
`ChannelGroupFuture`	`deregister(ChannelMatcher matcher)` Deprecated. This method will be removed in the next major feature release. Deregister all `Channel`s in this group from their `EventLoop` that are matched by the given `ChannelMatcher`. Please note that this operation is asynchronous as `ChannelOutboundInvoker.deregister()` is.
`ChannelGroupFuture`	`disconnect()` Disconnects all `Channel`s in this group from their remote peers.
`ChannelGroupFuture`	`disconnect(ChannelMatcher matcher)` Disconnects all `Channel`s in this group from their remote peers, that are matched by the given `ChannelMatcher`.
`Channel`	`find(ChannelId id)` Returns the `Channel` which has the specified `ChannelId`.
`ChannelGroup`	`flush()` Flush all `Channel`s in this group.
`ChannelGroup`	`flush(ChannelMatcher matcher)` Flush all `Channel`s in this group that are matched by the given `ChannelMatcher`.
`ChannelGroupFuture`	`flushAndWrite(Object message)` Deprecated. Use `writeAndFlush(Object)` instead.
`ChannelGroupFuture`	`flushAndWrite(Object message, ChannelMatcher matcher)` Deprecated. Use `writeAndFlush(Object, ChannelMatcher)` instead.
`String`	`name()` Returns the name of this group.
`ChannelGroupFuture`	`newCloseFuture()` Returns the `ChannelGroupFuture` which will be notified when all `Channel`s that are part of this `ChannelGroup`, at the time of calling, are closed.
`ChannelGroupFuture`	`newCloseFuture(ChannelMatcher matcher)` Returns the `ChannelGroupFuture` which will be notified when all `Channel`s that are part of this `ChannelGroup`, at the time of calling, are closed.
`ChannelGroupFuture`	`write(Object message)` Writes the specified `message` to all `Channel`s in this group.
`ChannelGroupFuture`	`write(Object message, ChannelMatcher matcher)` Writes the specified `message` to all `Channel`s in this group that are matched by the given `ChannelMatcher`.
`ChannelGroupFuture`	`write(Object message, ChannelMatcher matcher, boolean voidPromise)` Writes the specified `message` to all `Channel`s in this group that are matched by the given `ChannelMatcher`.
`ChannelGroupFuture`	`writeAndFlush(Object message)` Shortcut for calling `write(Object)` and `flush()`.
`ChannelGroupFuture`	`writeAndFlush(Object message, ChannelMatcher matcher)` Shortcut for calling `write(Object)` and `flush()` and only act on `Channel`s that are matched by the `ChannelMatcher`.
`ChannelGroupFuture`	`writeAndFlush(Object message, ChannelMatcher matcher, boolean voidPromise)` Shortcut for calling `write(Object, ChannelMatcher, boolean)` and `flush()` and only act on `Channel`s that are matched by the `ChannelMatcher`.

Methods inherited from interface java.util.Set
add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, remove, removeAll, retainAll, size, spliterator, toArray, toArray

Methods inherited from interface java.util.Collection
parallelStream, removeIf, stream

Methods inherited from interface java.lang.Iterable
forEach

Methods inherited from interface java.lang.Comparable
compareTo

- Method Detail
  - name
```
String name()
```
    Returns the name of this group. A group name is purely for helping you to distinguish one group from others.
  - find
```
Channel find(ChannelId id)
```
    Returns the Channel which has the specified ChannelId.
    
    Returns:
    
    the matching Channel if found. null otherwise.
  - write
```
ChannelGroupFuture write(Object message)
```
    Writes the specified message to all Channels in this group. If the specified message is an instance of ByteBuf, it is automatically duplicated to avoid a race condition. The same is true for ByteBufHolder. Please note that this operation is asynchronous as ChannelOutboundInvoker.write(Object) is.
    
    Returns:
    
    itself
  - write
```
ChannelGroupFuture write(Object message,
                         ChannelMatcher matcher)
```
    Writes the specified message to all Channels in this group that are matched by the given ChannelMatcher. If the specified message is an instance of ByteBuf, it is automatically duplicated to avoid a race condition. The same is true for ByteBufHolder. Please note that this operation is asynchronous as ChannelOutboundInvoker.write(Object) is.
    
    Returns:
    
    the ChannelGroupFuture instance that notifies when the operation is done for all channels
  - write
```
ChannelGroupFuture write(Object message,
                         ChannelMatcher matcher,
                         boolean voidPromise)
```
    Writes the specified message to all Channels in this group that are matched by the given ChannelMatcher. If the specified message is an instance of ByteBuf, it is automatically duplicated to avoid a race condition. The same is true for ByteBufHolder. Please note that this operation is asynchronous as ChannelOutboundInvoker.write(Object) is. If voidPromise is true ChannelOutboundInvoker.voidPromise() is used for the writes and so the same restrictions to the returned ChannelGroupFuture apply as to a void promise.
    
    Returns:
    
    the ChannelGroupFuture instance that notifies when the operation is done for all channels
  - flush
```
ChannelGroup flush()
```
    Flush all Channels in this group. If the specified messages are an instance of ByteBuf, it is automatically duplicated to avoid a race condition. Please note that this operation is asynchronous as ChannelOutboundInvoker.write(Object) is.
    
    Returns:
    
    the ChannelGroupFuture instance that notifies when the operation is done for all channels
  - flush
```
ChannelGroup flush(ChannelMatcher matcher)
```
    Flush all Channels in this group that are matched by the given ChannelMatcher. If the specified messages are an instance of ByteBuf, it is automatically duplicated to avoid a race condition. Please note that this operation is asynchronous as ChannelOutboundInvoker.write(Object) is.
    
    Returns:
    
    the ChannelGroupFuture instance that notifies when the operation is done for all channels
  - writeAndFlush
```
ChannelGroupFuture writeAndFlush(Object message)
```
    Shortcut for calling write(Object) and flush().
  - flushAndWrite
```
@Deprecated
ChannelGroupFuture flushAndWrite(Object message)
```
    Deprecated. Use writeAndFlush(Object) instead.
  - writeAndFlush
```
ChannelGroupFuture writeAndFlush(Object message,
                                 ChannelMatcher matcher)
```
    Shortcut for calling write(Object) and flush() and only act on Channels that are matched by the ChannelMatcher.
  - writeAndFlush
```
ChannelGroupFuture writeAndFlush(Object message,
                                 ChannelMatcher matcher,
                                 boolean voidPromise)
```
    Shortcut for calling write(Object, ChannelMatcher, boolean) and flush() and only act on Channels that are matched by the ChannelMatcher.
  - flushAndWrite
```
@Deprecated
ChannelGroupFuture flushAndWrite(Object message,
                                             ChannelMatcher matcher)
```
    Deprecated. Use writeAndFlush(Object, ChannelMatcher) instead.
  - disconnect
```
ChannelGroupFuture disconnect()
```
    Disconnects all Channels in this group from their remote peers.
    
    Returns:
    
    the ChannelGroupFuture instance that notifies when the operation is done for all channels
  - disconnect
```
ChannelGroupFuture disconnect(ChannelMatcher matcher)
```
    Disconnects all Channels in this group from their remote peers, that are matched by the given ChannelMatcher.
    
    Returns:
    
    the ChannelGroupFuture instance that notifies when the operation is done for all channels
  - close
```
ChannelGroupFuture close()
```
    Closes all Channels in this group. If the Channel is connected to a remote peer or bound to a local address, it is automatically disconnected and unbound.
    
    Returns:
    
    the ChannelGroupFuture instance that notifies when the operation is done for all channels
  - close
```
ChannelGroupFuture close(ChannelMatcher matcher)
```
    Closes all Channels in this group that are matched by the given ChannelMatcher. If the Channel is connected to a remote peer or bound to a local address, it is automatically disconnected and unbound.
    
    Returns:
    
    the ChannelGroupFuture instance that notifies when the operation is done for all channels
  - deregister
```
@Deprecated
ChannelGroupFuture deregister()
```
    Deprecated. This method will be removed in the next major feature release. Deregister all Channels in this group from their EventLoop. Please note that this operation is asynchronous as ChannelOutboundInvoker.deregister() is.
    
    Returns:
    
    the ChannelGroupFuture instance that notifies when the operation is done for all channels
  - deregister
```
@Deprecated
ChannelGroupFuture deregister(ChannelMatcher matcher)
```
    Deprecated. This method will be removed in the next major feature release. Deregister all Channels in this group from their EventLoop that are matched by the given ChannelMatcher. Please note that this operation is asynchronous as ChannelOutboundInvoker.deregister() is.
    
    Returns:
    
    the ChannelGroupFuture instance that notifies when the operation is done for all channels
  - newCloseFuture
```
ChannelGroupFuture newCloseFuture()
```
    Returns the ChannelGroupFuture which will be notified when all Channels that are part of this ChannelGroup, at the time of calling, are closed.
  - newCloseFuture
```
ChannelGroupFuture newCloseFuture(ChannelMatcher matcher)
```
    Returns the ChannelGroupFuture which will be notified when all Channels that are part of this ChannelGroup, at the time of calling, are closed.

Interface ChannelGroup

Broadcast a message to multiple Channels

Simplify shutdown process with ChannelGroup

Method Summary

Methods inherited from interface java.util.Set

Methods inherited from interface java.util.Collection

Methods inherited from interface java.lang.Iterable

Methods inherited from interface java.lang.Comparable

Method Detail

name

find

write

write

write

flush

flush

writeAndFlush

flushAndWrite

writeAndFlush

writeAndFlush

flushAndWrite

disconnect

disconnect

close

close

deregister

deregister

newCloseFuture

newCloseFuture

Broadcast a message to multiple `Channel`s

Simplify shutdown process with `ChannelGroup`