In most cases, almost all cases there will be data to be read when a
READ event occurs.
An example where there is none, is when we recieve a request, and there
is no data in the body yet.
as we parse the GET request, we invoke READ so that you can read any
client data, if any.
And that is the case when it returns 0, a fully valid use case.
Filip
Christophe Pierret wrote:
OK, I understand your rationale.
It is a tough job to retrofit asynchronous IOs in a synchronous framework like the
"servlet specification" and you did great given the constraints !
Continue the good job...
Christophe
-----Message d'origine-----
De : Remy Maucherat [mailto:[EMAIL PROTECTED]
Envoyé : mercredi 24 janvier 2007 14:48
À : Tomcat Developers List
Objet : Re: Comet API and InputStream.available()
Christophe Pierret wrote:
Here is what I understood:
Assumption #1: ================ When you receive a
CometEvent.EventType.READ event, you can always read() at least one
byte from the request's InputStream without blocking.
Is this correct ? If not correct, then this mail goes directly to
trash (and sorry for the inconvenience...)
It's not 100% correct: you may do one blocking read without waiting for client input (as
the poller signaled data was available). However, the InputStream that is given to you in
the Servlet is a buffered stream that has no relation with the socket. I don't like the
idea of returning "1", which is a hack. The only non hack way of doing it is to
do the read somewhere (in CometAdapter.event) to fill the buffer of the input stream
before calling the Servlet.
At the moment, I use this read method (which is compatible with both behaviors
of available()) in the chat servlet from the examples:
do {
int n = is.read(buf);
if (n > 0) {
log("Read " + n + " bytes: " + new String(buf, 0, n)
+ " for session: " + request.getSession(true).getId());
} else if (n < 0) {
// Error: do cleanup
event.close();
return;
}
} while (is.available() > 0);
Rémy
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