That's also how AsyncWeb is implemented, incidentally, with a separate
encoder and decoder stored as a session attribute for each session. The
code for HttpServerCodecFactory does this with the following:
public ProtocolDecoder getDecoder() throws Exception {
(topLevelState creation omitted)
return new StateMachineProtocolDecoder(topLevelState);
}
public ProtocolEncoder getEncoder() throws Exception {
return new OneShotHttpResponseEncoder();
}
This seems preferable to me, honestly, as it's just less complicated.
-Adam
On 6/22/07, Adam Fisk <[EMAIL PROTECTED]> wrote:
Hi Maarten-
Thanks for the link to that discussion thread. It seems like there's
quite a bit of confusion on this point, though. The thread really didn't
reach a common consensus in my reading of it.
> Indeed, I want thread-2 to see the changes made by thread-1.
> But without synchronization, there is no such guarantee.
Right, but the tutorial snippet says "MINA ensures that there will never
be more than one thread simultaneously executing the decode() function for
the same IoSession". For that to be true, there's gotta be some
synchronization somewhere. I decided to dig into the code a little bit for
the 1.1.0 branch, and indeed ProtocolCodecFilter has the following:
try
{
synchronized( decoderLock )
{
decoder.decode( session, in, decoderOut );
}
}
With the code above, the changes made by thread-1 on the decoder *are
guaranteed to be seen by thread-2*. Now, I realize this is an
implementation detail of 1.1.0, but the tutorial description above seems
to be relying on that detail. So it seems like it should be totally fine to
have a ProtocolCodecFactory that returns a new decoder on each getDecoder
call (effectively one decoder per session). I still don't see the
disadvantage of doing this.
It certainly seems less complicated that way!
Thanks again for your patience Maarten. Seems like a key point we should
all be clear on, so that's why I'm trying to dig a little deeper here.
-Adam
