[infinispan-dev] @Marshallable as an option for end user externalizers?

[Galder Zamarreño]

On Mar 16, 2011, at 7:18 PM, Manik Surtani wrote:

> 
> On 16 Mar 2011, at 18:14, Galder Zamarreño wrote:
> 
>> Hi,
>> 
>> Some feedback has come saying that it'd be nice to be able to configure externalizers using annotations. Now, in a previous discussion (http://lists.jboss.org/pipermail/infinispan-dev/2010-December/007047.html) it was agreed that for framework developers this is not nice since it makes it hard to abstract the Infinispan layer, but end users might be interested in using annotations rather than having to implement getId(), getTypeClasses() in Externalizer interface - see http://community.jboss.org/docs/DOC-16198 
>> 
>> To be able to support this, @Marshallable annotation that would be used wth externalizer implementations would have to be brought back with id and typeClasses attributes. That'd make it a 3rd way to define ids, after XML and getId() implementations.
>> 
>> Clearly, getId() and getTypeClasses() would be moved to a different interface, so that people that chose to use @Marshallable could just provide read/writeObject method implementations.
>> 
>> The gain from having end users use @Marshallable is not that great IMO cos we don't do annotation scanning, so there would still be a need to register externalizers.
> 
> Why don't we do annotation scanning?  We maintain a table of externalizers keyed on class, right?  So why not scan each new type (the first time we encounter it) for @Marshallable to compile this externalizer table on the fly?
> 
> Is it to do with classloader leaks?  If so, a weak map could be used for this table... 

You misunderstood what I meant. By annotation scanning I meant that we won't be scanning the entire classpath for user classes that have @Marshaller, right? I mean, we don't do like an EJB container that goes through deployments checking for all @EJB classes, cos that would be very expensive and it's not our business. So, back to my question, the users will still need to give us the list of user defined externalizers. Sure, we can do annotation scanning on that specific list of classes. 

My point is that it might look nice that users can use annotations to define some externalizer properties (id and typeClasses) but they're not getting as much out of it as they'd with @EJBs in an EJB container cos they have to list the externalizers somehow. Again, unless you wanna get into classpath annotation search...

> 
> Cheers
> Manik
> 
> --
> Manik Surtani
> manik at jboss.org
> twitter.com/maniksurtani
> 
> Lead, Infinispan
> http://www.infinispan.org
> 
> 
> 
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--
Galder Zamarreño
Sr. Software Engineer
Infinispan, JBoss Cache