Hi Fernando,
On 1/25/07, Fernando C. de Castro <[EMAIL PROTECTED]> wrote:
Hello,
I am trying to do something that I don't even know is possible. Can I
change the codec "on the fly"?
Let me try and explain what I'm doing so you guys can follow my thoughts.
On my SessionHandler (extends IoHandlerAdapter) I add a Codec to the
session as it's created:
public void sessionCreated( IoSession session )
{
session.getFilterChain().clear();
session.getFilterChain().addFirst (
"idcodec",
new ProtocolCodecFilter(new
IDprotocolCodecFactory()));
}
OK, so it loads my IDprotocolCodecFactory which has one messageEncoder and
one messageDecoder:
public class IDprotocolCodecFactory extends DemuxingProtocolCodecFactory
{
public IDprotocolCodecFactory () {
super.register(IDmessageDecoder.class);
super.register(IDmessageEncoder.class);
}
}
This messageDecoder waits for 2 bytes, analyses them then returns
MessageDecoderResult.OK , and that fires the messageReceived() on my
SessionHanlder. So far, working as expected.
Then, I would like to change the Codec (e.g. the "identification stage" is
over, now the server expects another kind of messages). So, on the
messageReceived(), I try to change the codec:
public void messageReceived( IoSession session, Object message )
{
if (session.getFilterChain().contains("idcodec")){
session.getFilterChain().remove("idcodec");
session.getFilterChain().addFirst (
"messagecodec",
new ProtocolCodecFilter(new
MyMessageCodecFactory()));
}
else {
// after the "idcodec" was removed from the chain and
"messagecodec" was placed instead,
// messageReceived() will be triggered by "messagecodec" and will
always get to this 'else'.
// (or so I expect...)
}
}
The MyMessageCodecFactory class is similar the presented
IDprotocolCodecFactory (extends DemuxingProtocolCodecFactory )
Is it possible to change the codec like this? Because it's not
working. It's like I'm stuck with "idcodec" forever, it never changes to
"messagecodec".
You can if there's a contract between you and your remote peer that the
remote peer doesn't send any message while you switch your codec. If not,
the idcodec can receive unwanted data, or data will be received when no
codec is in action.
You can work around this problem by creating a codec that delegates to the
two child codecs appropriately. Of course, we will introduce an easier way
to replace the codec on the fly like this in 2.0:
session.getFilterChain().replace("codec", newCodec);
HTH,
Trustin
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