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From Emmanuel Lecharny <elecha...@gmail.com>
Subject Re: [MINA 3.0] filter chains
Date Fri, 26 Aug 2011 14:47:48 GMT
On 8/26/11 4:28 PM, Alan D. Cabrera wrote:
> On Aug 26, 2011, at 7:12 AM, Julien Vermillard wrote:
>> On Fri, Aug 26, 2011 at 4:07 PM, Emmanuel Lecharny<elecharny@gmail.com>  wrote:
>>> On 8/26/11 3:44 PM, Alan D. Cabrera wrote:
>>>> On Aug 26, 2011, at 6:40 AM, Julien Vermillard wrote:
>>>>> On Fri, Aug 26, 2011 at 3:24 PM, Alan D. Cabrera<list@toolazydogs.com>
>>>>>   wrote:
>>>>>> On Aug 26, 2011, at 4:14 AM, Julien Vermillard wrote:
>>>>>>> I modified the API to remove IoFilterChain. Now you are supposed
>>>>>>> give a list of filter to the service before starting it :
>>>>>>> // create the fitler chain for this service
>>>>>>> List<IoFilter>   filters = new ArrayList<IoFilter>();
>>>>>>> filters.add(new LoggingFilter("byte log filter"));
>>>>>>> filters.add(new MyCodecFilter());
>>>>>>> filters.add(new LoggingFilter("pojo log filter"));
>>>>>>> filters.add(newMyProtocolLogicFilter());
>>>>>>> acceptor.setFilters(filters);
>>>>>>> acceptor.bind(...);
>>>>>> How do we make chains where two filters feed into one or one filter
>>>>>> feeds two filters?  If you look in my sandbox we can accommodate
this via:
>>>>>> static import a.m.util.Util. linkParentWithChild; // to be written
>>>>>> IoFilter foo = new FooFilter();
>>>>>> LinkStateFilter link = new LinkStateFilter();
>>>>>> IoFilter checksum = new ChecksumFilter();
>>>>>> IoFilter log = new LogFilter();
>>>>>> link.addLinkStateListener(foo);
>>>>>> linkParentWithChild(foo, checksum);
>>>>>> linkParentWithChild(link, checksum);
>>>>>> linkParentWithChild(checksum, log);
>>>>>> acceptor.setFilters(foo);
>>>>> About the code in the sandbox :
>>>>> http://svn.apache.org/repos/asf/mina/sandbox/adc/ahc/mina3/src/main/java/org/apache/mina/core/IoFilter.java
>>>>> I see no IoFilter.addLinkStateListener(..) method, am I looking at the
>>>>> right place ?
>>>> Oops, it was meant to just be a sketch.  :)
>>>>> About the "filters feed into one or one filter feeds two filters", do
>>>>> you have a concrete use case in mind for that ?
>>>> The above example does, Foo and the link state filter.  I'm sure that
>>>> we've discussed this before.  Another example is a mux/demux situation. 
>>>> would all of this fit into the grand scheme of things?
>>> Yeah, it really should be a graph of filters, not a list of filters.
>> Well if it's just for demuxing I proposed few mails ago this solution
>> : http://s.apache.org/A9W
> I think we need to make graphing a 1st class citizen and not buried inside another filter

I do agree. The proposed solution on http://s.apache.org/A9W is what we 
currently have, and it's tedious to manage.

It would be way better to be able to let the controler call the next 
filter based on an evaluation method based on the current state.

Now, the question is : how do the controller knows which filter to call 
next ? It must have the current state, and it must be able to make the 

For instance, let's say that from filter F we can switch to either 
filter G or filter H, depending on the state we transit to in F.

F --(state1)--> G
F --(state2)--> H

That means the controller has a map { (F, state1, G), (F, state2, H)} 
somewhere. State should be passed to the controller too :

controller.nextFilter( newState );

Pretty theorical at this point... I'm sorry not to have a lot of time to 
code this, I do realize that for you guys implementing ideas it's a PITA...

Emmanuel L├ęcharny

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