best way to attach metadata to a channel

[Norman Maurer]

Hi there,

I think the best explaintation can be found here:

http://docs.jboss.org/netty/3.2/api/org/jboss/netty/channel/ChannelHandler.html

Bye,
Norman


2011/9/22 Steve Coughlan <shadders.del at gmail.com>:
> I'm building a proxy for a binary protocol that will multiple chanels
> on either side.  Each channel can be obtained either by a server or a
> client and once they are obtained I will treat them identically.
>
> I need to attach metadata to each channel that is easily accessable
> from the handler.messageReceived(ChannelHandlerContext ctx,
> MessageEvent e) method.  My metadata class is NodeChannel and contains
> a reference to the channel itself.
>
> I'd prefer to avoid subclassing Channel as that then ties me to a
> particular transport implementation.
>
> It would seem the logical way is use
> ChannelHandlerContext.getAttachment but I am not entirely clear if
> there's a one to one relationship between ChannelHandlerContext and
> Channel.  If I keep a reference to ChannelHandlerContext in
> NodeChannel rather than the channel can I garuntee that it's
> getChannel will always return the same channel object?  And I can I
> garuntee that will only ever be one instance of ChannelHandlerContext
> that will return that channel?
>
> I'd really prefer to avoid doing a map lookup with channel as key to
> obtain the metadata.  Many message will simply be ignored so this
> would be a serious waste of resources.
>
> Also can someone tell me when ctx is populated with a channel.  I'm
> trying to obtain a reference within channelOpen but it's returning
> null at that stage.
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