io.netty.channel.group

Interface ChannelGroup

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 Channels

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

Method Summary

Methods

Modifier and Type	Method and Description
ChannelGroupFuture	close() Closes all Channels in this group.
ChannelGroupFuture	close(ChannelMatcher matcher) Closes all Channels in this group that match the given ChannelMatcher.
ChannelGroupFuture	deregister() Deregister all Channels in this group from their EventLoop.
ChannelGroupFuture	deregister(ChannelMatcher matcher) Deregister all Channels in this group from their EventLoop that match the given ChannelMatcher.
ChannelGroupFuture	disconnect() Disconnects all Channels in this group from their remote peers.
ChannelGroupFuture	disconnect(ChannelMatcher matcher) Disconnects all Channels in this group from their remote peers, that match the given ChannelMatcher.
Channel	find(ChannelId id) Returns the Channel which has the specified ChannelId.
ChannelGroup	flush() Flush all Channels in this group.
ChannelGroup	flush(ChannelMatcher matcher) Flush all Channels in this group that match the given ChannelMatcher.
String	name() Returns the name of this group.
ChannelGroupFuture	write(Object message) Writes the specified message to all Channels in this group.
ChannelGroupFuture	write(Object message, ChannelMatcher matcher) Writes the specified message to all Channels in this group that match 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 Channels that match the ChannelMatcher.

Methods inherited from interface java.util.Set

add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray

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 Channel.write(Object) is.

Returns:

itself

write

ChannelGroupFuture write(Object message,
                       ChannelMatcher matcher)

Writes the specified message to all Channels in this group that match 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 Channel.write(Object) is.

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 Channel.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 match 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 Channel.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().

writeAndFlush

ChannelGroupFuture writeAndFlush(Object message,
                               ChannelMatcher matcher)

Shortcut for calling write(Object) and flush() and only act on Channels that match the ChannelMatcher.

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 match 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 match 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

ChannelGroupFuture deregister()

Deregister all Channels in this group from their EventLoop. Please note that this operation is asynchronous as Channel.deregister() is.

Returns:

the ChannelGroupFuture instance that notifies when the operation is done for all channels

deregister

ChannelGroupFuture deregister(ChannelMatcher matcher)

Deregister all Channels in this group from their EventLoop that match the given ChannelMatcher. Please note that this operation is asynchronous as Channel.deregister() is.

Returns:

the ChannelGroupFuture instance that notifies when the operation is done for all channels