[infinispan-dev] [Pull Request] Modular Classloading Compatibility

[Manik Surtani]

On 27 Apr 2011, at 12:39, Jason T. Greene wrote:

> Available here:
> https://github.com/infinispan/infinispan/pull/278
> 
> The problem is basically that infinispan currently is using TCCL for all 
> class loading and resource loading. This has a lot of problems in 
> modular containers (OSGi, AS7, etc), where you dont have framework 
> implementation classes on the same classloader as user classes (that is 
> how they achieve true isolation)
> 
> You can read about this in more detail here:
> http://community.jboss.org/wiki/ModuleCompatibleClassloadingGuide
> 
> The patch in the pull request is a first step, and should fix many 
> issues, but it does not address all (there is still a lot of TCCL usage 
> spread out among cacheloaders and so on), and ultimately it's just a 
> work around. It should, however, be compatible in any other non-modular 
> environment.
> 
> Really the ultimate solution is to setup a proper demarcation between 
> what the user is supposed to provide, and what is expected to be bundled 
> with infinispan. Whenever there is something the user can provide a 
> class, then the API should accept a classloader to load that class from. 

As in, user API?  That's a little intrusive... e.g., put(K, V, cl) ?

> If it's a class that is just internal wiring of infinispan, then 
> Infinispan's defining classloader should always be used.
> 
> The one case I can think of in infnispan where TCCL really makes sense 
> is in the case of lazy deserialization from an EE application. However 
> that is only guaranteed to work when you are executing in a context that 
> has that style of contract (like in an EE component). There are many 
> other cases though where someone would expect it to work from a non-EE 
> context (e.g. from a thread pool). What you really want is the caller's 
> classloader, but that is not cheap to get at, so it's something that 
> should be supplied as part of the API interaction (in the case where 
> there is no EE context). Alternatively you can just just require that 
> folks push/pop TCCL, but users often get this wrong.
> 
> Thanks!
> 
> -- 
> Jason T. Greene
> JBoss, a division of Red Hat
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--
Manik Surtani
manik at jboss.org
twitter.com/maniksurtani

Lead, Infinispan
http://www.infinispan.org