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Posted to dev@mina.apache.org by Michael Bauroth <mi...@falcom.de> on 2006/04/12 08:13:27 UTC
How do ProtocolDecoders work in a chain?
Hi,
sorry for the cross-posting (original question is located in
'Implementation details'). On the other side I think it's meaningful to
extract this question out there because it could be helpful for other
developers too.
My question: What happens with the output (ProtocolDecoderOutput -
POJOs) of different protocol decoders in a chain? Will it be sent
directly to the IoSession or can I receive and modify it in other
decoders, which are inserted later in the chain?
Sample: ByteBuffer -> TextLineDecoder (works on ByteBuffer) -> (single
lines / Strings as POJOs) -> ???? -> OwnDecoder (works on ByteBuffer /
POJO ???)
Hope you can make the stuff clear for me.
Regards
Michael
Re: How do ProtocolDecoders work in a chain?
Posted by Michael Bauroth <mi...@falcom.de>.
Thanx for the quick response ...
Trustin Lee wrote:
> Hi Michael,
>
> My question: What happens with the output (ProtocolDecoderOutput -
>
>>POJOs) of different protocol decoders in a chain? Will it be sent
>>directly to the IoSession or can I receive and modify it in other
>>decoders, which are inserted later in the chain?
>
>
>
> ProtocolEncoder and ProtocolDecoder are wrapped by ProtocolCodecFilter,
> which is an IoFilter. So It becomes a part of the whole chain for an
> IoSession. No filters are allowed to send events to IoHandler directly.
> It's an implicit principal.
>
> If you inserted one ProtocolCodecFilter, then it will be passed to
> IoHandler.messageReceived because there's no more filters in the chain.
> Otherwise, the object, as a result of decoding, will be passed to the next
> filter in the chain.
>
> You can layer two ProtocolCodecFilters because already decoded messages are
> not processed by the second ProtocolCodecFilter. Only ByteBuffers will be
> decoded. You can use this trick to implement your protocol as a
> multi-layered stack.
This means on the other side:
... codecs behind TextLineCodec shouldn't work when all the input was
line based, because all the stuff is decoded yet in TextLineCodec to
single lines?
... if I want to use line separation among with other decoding
algorithms, i must overload TextLineCodec itself or implement codec with
equivalent functionality instead of using it as "preprocessor" in my chain?
Regards
Michael
>
> HTH,
> Trustin
> --
> what we call human nature is actually human habit
> --
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>
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Re: How do ProtocolDecoders work in a chain?
Posted by Trustin Lee <tr...@gmail.com>.
Hi Michael,
On 4/12/06, Michael Bauroth <mi...@falcom.de> wrote:
>
> Hi,
>
> sorry for the cross-posting (original question is located in
> 'Implementation details'). On the other side I think it's meaningful to
> extract this question out there because it could be helpful for other
> developers too.
No problem. :)
My question: What happens with the output (ProtocolDecoderOutput -
> POJOs) of different protocol decoders in a chain? Will it be sent
> directly to the IoSession or can I receive and modify it in other
> decoders, which are inserted later in the chain?
ProtocolEncoder and ProtocolDecoder are wrapped by ProtocolCodecFilter,
which is an IoFilter. So It becomes a part of the whole chain for an
IoSession. No filters are allowed to send events to IoHandler directly.
It's an implicit principal.
If you inserted one ProtocolCodecFilter, then it will be passed to
IoHandler.messageReceived because there's no more filters in the chain.
Otherwise, the object, as a result of decoding, will be passed to the next
filter in the chain.
You can layer two ProtocolCodecFilters because already decoded messages are
not processed by the second ProtocolCodecFilter. Only ByteBuffers will be
decoded. You can use this trick to implement your protocol as a
multi-layered stack.
HTH,
Trustin
--
what we call human nature is actually human habit
--
http://gleamynode.net/
--
PGP key fingerprints:
* E167 E6AF E73A CBCE EE41 4A29 544D DE48 FE95 4E7E
* B693 628E 6047 4F8F CFA4 455E 1C62 A7DC 0255 ECA6
Re: How do ProtocolDecoders work in a chain?
Posted by Niklas Therning <ni...@trillian.se>.
Niklas Therning wrote:
> Michael Bauroth wrote:
>
>> ...
>>
>> My question: What happens with the output (ProtocolDecoderOutput -
>> POJOs) of different protocol decoders in a chain? Will it be sent
>> directly to the IoSession or can I receive and modify it in other
>> decoders, which are inserted later in the chain?
>>
>> Sample: ByteBuffer -> TextLineDecoder (works on ByteBuffer) -> (single
>> lines / Strings as POJOs) -> ???? -> OwnDecoder (works on ByteBuffer
>> / POJO ???)
>
>
> Message objects created by a decoder will passed on to the next filter
> in the chain. If the ProtocolCodecFilter is the last filter in the chain
> the decoded message will be passed on to your IoHandler implementation.
>
> You could definitely chain ProtocolCodecFilters which use different
> decoders. However, you must make sure they are compatible. The first
> decoders output must be compatible with the second decoders input etc.
> For example, both TextLineDecoder and the decoders created by
> DemuxingProtocolCodecFactory expects the input to be ByteBuffers. This
> means you cannot chain them.
Ok, after reading Trusin's reply I must correct myself. You can chain
ProtocolCodecFilters but the second decoder will only be used if the
first decoder emitts a ByteBuffer. Otherwise, the second decoder will be
ignored.
/Niklas
Re: How do ProtocolDecoders work in a chain?
Posted by Niklas Therning <ni...@trillian.se>.
Michael Bauroth wrote:
> ...
>
> My question: What happens with the output (ProtocolDecoderOutput -
> POJOs) of different protocol decoders in a chain? Will it be sent
> directly to the IoSession or can I receive and modify it in other
> decoders, which are inserted later in the chain?
>
> Sample: ByteBuffer -> TextLineDecoder (works on ByteBuffer) -> (single
> lines / Strings as POJOs) -> ???? -> OwnDecoder (works on ByteBuffer /
> POJO ???)
Message objects created by a decoder will passed on to the next filter
in the chain. If the ProtocolCodecFilter is the last filter in the chain
the decoded message will be passed on to your IoHandler implementation.
You could definitely chain ProtocolCodecFilters which use different
decoders. However, you must make sure they are compatible. The first
decoders output must be compatible with the second decoders input etc.
For example, both TextLineDecoder and the decoders created by
DemuxingProtocolCodecFactory expects the input to be ByteBuffers. This
means you cannot chain them.
/Niklas