[infinispan-dev] Defining new commands in modules

[Manik Surtani]

On 11 Oct 2010, at 13:44, Mircea Markus wrote:

>> 
>> PS: There is no JIRA for this.  If we like this approach and it works, I suggest we create a JIRA and implement it for 4.2.  The impl should be simple once we resolve the outstanding bits.
> there is one actually: https://jira.jboss.org/browse/ISPN-256
> I'll attache the patches to it.
> Just to conclude, I've POC both approaches GenericCommand and ExtendingCommand, here are my thoughts on it:
> - extending visitor
> PROS:  ExtendingCommand is a better OO API, more strongly typed
> CONS: it is harder for the user to understand; integrating custom serialization might be difficult(impossible at the time), also it will have to manage command uniques. 

Why is this hard for developers to understand?  Remember, these aren't *application* developers, but people *extending* Infinispan.  They already ought to have an in-depth knowledge of Infinispan.

What do you mean by "command uniques"?

> - GenericCommand
> CONS: 
> - less OO API
> - would require a "convention" for not "overusing" it. Overuse would be in client code though, not in ours

Client code may well be our code.  E.g., more modules that we ship.  -1 to a weakly typed API like this.  Conventions cannot be enforced, and IMO if something can be abused, then it will be abused.  :)

> PROS:
> - easier for the user to understand and use
> 	- no need for extra classes needed
> 	- no understanding of how the interceptor chain internals work needed (for writing acceptVisitor). 

Why would someone write a visitable command and not care about an interceptor that visits it?  Surely you would only write a visitable command if you *want* to visit it with an interceptor.

> 	- no understanding of how serialization works  is needed. Nor command uniques.

?  What's so hard about this?  "implements Externabilzable" is the easy way, @Marshallable() a slightly more roundabout way for greater efficiency in marshalling.

> - easy streight-forward solutions
> 
> I would go for GenericCommand, but Extending approach works for me as well.

--
Manik Surtani
manik at jboss.org
Lead, Infinispan
Lead, JBoss Cache
http://www.infinispan.org
http://www.jbosscache.org




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