public interface ChannelEvent
Channel.
A ChannelEvent is handled by a series of ChannelHandlers in
a ChannelPipeline.
Every event is either an upstream event or a downstream event.
If an event flows forward from the first handler to the last handler in a
ChannelPipeline, we call it an upstream event and say "an
event goes upstream." If an event flows backward from the last
handler to the first handler in a ChannelPipeline, we call it a
downstream event and say "an event goes downstream."
(Please refer to the diagram in ChannelPipeline for more explanation.)
When your server receives a message from a client, the event associated with
the received message is an upstream event. When your server sends a message
or reply to the client, the event associated with the write request is a
downstream event. The same rule applies for the client side. If your client
sent a request to the server, it means your client triggered a downstream
event. If your client received a response from the server, it means
your client will be notified with an upstream event. Upstream events are
often the result of inbound operations such as InputStream.read(byte[]),
and downstream events are the request for outbound operations such as
OutputStream.write(byte[]), Socket.connect(SocketAddress),
and Socket.close().
| Event name | Event type and condition | Meaning | |
|---|---|---|---|
"messageReceived" |
MessageEvent |
a message object (e.g. ChannelBuffer) was received from a remote peer |
|
"exceptionCaught" |
ExceptionEvent |
an exception was raised by an I/O thread or a ChannelHandler |
|
"channelOpen" |
ChannelStateEvent(state = OPEN, value = true) |
a Channel is open, but not bound nor connected |
Be aware that this event is fired from within the I/O thread. You should never execute any heavy operation in there as it will block the dispatching to other workers! |
"channelClosed" |
ChannelStateEvent(state = OPEN, value = false) |
a Channel was closed and all its related resources were released |
|
"channelBound" |
ChannelStateEvent(state = BOUND, value = SocketAddress) |
a Channel is open and bound to a local address, but not connected. |
Be aware that this event is fired from within the I/O thread. You should never execute any heavy operation in there as it will block the dispatching to other workers! |
"channelUnbound" |
ChannelStateEvent(state = BOUND, value = null) |
a Channel was unbound from the current local address |
|
"channelConnected" |
ChannelStateEvent(state = CONNECTED, value =
SocketAddress) |
a Channel is open, bound to a local address, and connected to a remote address |
Be aware that this event is fired from within the I/O thread. You should never execute any heavy operation in there as it will block the dispatching to other workers! |
"writeComplete" |
WriteCompletionEvent |
something has been written to a remote peer | |
"channelDisconnected" |
ChannelStateEvent(state = CONNECTED, value = null) |
a Channel was disconnected from its remote peer |
|
"channelInterestChanged" |
ChannelStateEvent(state = INTEREST_OPS, no value) |
a Channel's interestOps was changed |
These two additional event types are used only for a parent channel which
can have a child channel (e.g. ServerSocketChannel).
| Event name | Event type and condition | Meaning |
|---|---|---|
"childChannelOpen" |
ChildChannelStateEvent( childChannel.isOpen() = true) |
a child Channel was open (e.g. a server channel accepted a connection.) |
"childChannelClosed" |
ChildChannelStateEvent( childChannel.isOpen() = false) |
a child Channel was closed (e.g. the accepted connection was closed.) |
| Event name | Event type and condition | Meaning |
|---|---|---|
"write" |
MessageEvent | Send a message to the Channel. |
"bind" |
ChannelStateEvent(state = BOUND, value = SocketAddress) |
Bind the Channel to the specified local address. |
"unbind" |
ChannelStateEvent(state = BOUND, value = null) |
Unbind the Channel from the current local address. |
"connect" |
ChannelStateEvent(state = CONNECTED, value =
SocketAddress) |
Connect the Channel to the specified remote address. |
"disconnect" |
ChannelStateEvent(state = CONNECTED, value = null) |
Disconnect the Channel from the current remote address. |
"close" |
ChannelStateEvent(state = OPEN, value = false) |
Close the Channel. |
Other event types and conditions which were not addressed here will be
ignored and discarded. Please note that there's no "open" in the
table. It is because a Channel is always open when it is created
by a ChannelFactory.
Please refer to the ChannelHandler and ChannelPipeline
documentation to find out how an event flows in a pipeline and how to handle
the event in your application.
| Modifier and Type | Method and Description |
|---|---|
Channel |
getChannel()
Returns the
Channel which is associated with this event. |
ChannelFuture |
getFuture()
Returns the
ChannelFuture which is associated with this event. |
ChannelFuture getFuture()
ChannelFuture which is associated with this event.
If this event is an upstream event, this method will always return a
SucceededChannelFuture because the event has occurred already.
If this event is a downstream event (i.e. I/O request), the returned
future will be notified when the I/O request succeeds or fails.