Nope, java.lang.reflect.Proxy won't work either, because of things like:
ChannelInitializer:
void initChannel(Channel ch) throws Exception {
String me = ch.context(this).name();
ch.pipeline().addAfter(me, null, new WhateverHandler());
}
fails with a NullPointerException because context(this) returns null,
because "this" is not actually in the pipeline(), Proxy(this) is!
Sigh!
While in theory, I could extend handlerAdded(ctx) and save a ref to the ctx
to be used in initChannel(), that would work for my own code, but is
unlikely to work for anyone else's!
Perhaps there is a way to achieve what I want without the shenanigans?
What I'm ultimately trying to do is "blame" the ChannelHandler that throws
an Exception.
So while I can implement exceptionCaught() in the last handler of the
pipeline, and catch the Exception, it's impossible to know which
ChannelHandler actually threw that Exception, other than by stepping
through the stackTrace, and looking for my own code (or Netty code, as the
case may be!) However, if there is more than one instance of a particular
ChannelHandler (e.g. tunnelling SSL in SSL), that still doesn't tell you
which *instance* threw the exception.
My solution to that was to alternate legitimate ChannelHandlers with an
ExceptionCatcher ChannelHandler. Each ExceptionCatcher has a reference to
the ChannelHandler before it. The first ExceptionCatcher to have its
exceptionCaught() method called can blame the ChannelHandler immediately
preceding it.
HOWEVER, should that ChannelHandler remove itself from the pipeline, or
insert other ChannelHandlers, it all falls down, because the
ExceptionCatcher gets left behind!
An alternative way to approach this would be to extend
DefaultChannelPipeline, but that kind of thing seems to be deprecated in
netty 4.
Any suggestions?
Thanks!
Rogan
On Wed, Mar 21, 2018 at 3:56 PM Rogan Dawes <[email protected]> wrote:
> I guess I could try using Java.lang.reflect.Proxy to wrap the class and
> supplement handlerRemoved.
>
> Should work ok, I think.
>
> Rogan
> On Wed, 21 Mar 2018 at 10:59 'Norman Maurer' via Netty discussions <
> [email protected]> wrote:
>
>> No there is nothing like that.
>>
>> Bye
>> Norman
>>
>>
>> On 20. Mar 2018, at 21:53, Rogan Dawes <[email protected]> wrote:
>>
>> Hi folks,
>>
>> I'm trying to monitor changes to the pipeline, and wondering if there is
>> any way to be notified when a handler is removed from a pipeline?
>>
>> By that I mean, independently of the specific handler's
>> handlerRemoved(ctx) method call. I'd like to be able to tell when a
>> particular handler is removed, without having to extend it and override
>> that method on every single handler.
>>
>> From what I can see, the only way to do it at the moment is by using
>> Aspect-Oriented programming, and decorating each handler that is added (a
>> slight difference from manually extending each handler).
>>
>> Am I missing something?
>>
>> Thanks!
>>
>> Rogan
>>
>>
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