Design question / getting reference to another handler - best practice

[Robert Wahlstedt]

On Oct 25, 2009, at 18:30 , Peter Thomas wrote:

> I have a client pipeline for e.g. (towards server): A --> B (assume  
> they handle both upstream / downstream)
>
> B encodes / decodes using a "chunk size" that can be changed by a  
> server message.
>
> But the business logic of unpacking a "chunk size change" message is  
> responsibility of A.
>
> I guess I have the following options of getting a reference to B and  
> calling a setter.
>
> - initialize the pipeline so that A has a reference to B
> - invent a new "internal" message and send it from A to B  (but  
> extra message clutter, downcast / if-then)
> - call methods on ChannelPipeline to get a reference to B
> - use a ChannelLocal or attachment (but seems to be handler specific)
>
> Any advice on which of the above would be recommended / discouraged,  
> would be greatly appreciated, maybe there are more ways I have missed.

I had a similar issue where I needed different handlers to have access  
to a "User" object.

I solved it by subclassing DefaultChannelPipeline and putting the User  
variable there. That way all of my handlers can access it by  
ChannelHandlerContext.getPipeline()

Not sure if this is the optimal way to deal with it, but it has been  
working for me. I'm interested in other suggestions as well.


/Rob