Hi Trustin,
Trustin Lee schrieb:
Hi Stefan,
On 2/1/07, Stefan Bischof <[EMAIL PROTECTED]> wrote:
Now I have a question regarding errors:
Scenario:
The client sends me a message which violates the protocol. As far as I
understood, this problem should be detected in
IcapRequestDecoder.decode. Right?
Yes, you can *detect* the problem, but you could also just do what you
are
supposed to do (i.e. parsing the message) and let the exception arise
due to
a unexpected value. You don't need to perform every integrity check on a
received message as long as an exception can be thrown.
Once an exception is throw from a ProtocolDecoder, MINA wraps the
exception
with ProtocolDecoderException, and forward it to your IoHandler's
exceptionCaught() handler method. You can check the type of the cause
(exception) using 'instanceof' keyword:
if (cause instanceof ProtocolDecoderException) {
Throwable causeOfCause = cause.getCause(); // what is thrown from
ProtocolDecoder
session.write(new FourOhOhMessage());
}
Thanks! I just tried and it naturally worked (after realizing some
strange eclipse behaviour, but thats another story). I just wasn't sure
about the 'MINA-way' of handling protocol decoding error issues.
I've never thought about using MessageDecoderResult.NOT_OK, but using
ProtocolDecoderException is better IMHO. It sounds interesting though.
I wasn't sure what the NOT_OK is really for. But then I found a line in
the Javadoc for MessageDecoder.decode (the returns-section): "Returns:
[...] NOT_OK if you cannot decode current message due to protocol
specification violation.", and I thought, "hey, this is what I need". In
which case would you really need NOT_OK?
HTH,
Trustin
Thanks for your help.
BTW: If you are interested, I could translate tutorials to german (when
they are ready).
regards,
Stefan Bischof
