[jbosscache-dev] JBCACHE-752 - marshalling response values to methodcalls

[Manik Surtani]

I have a prelim fix for JBCACHE-752 in HEAD.  I know it's a little  
hacky, but couldn't come up with a better solution without  
significantly reengineering a lot of stuff.  Here's where the problem  
lies.  Note that this only pertains to when region-based marshalling  
is used.

1)  When marshalling method calls, we run through a switch statement  
on method id to determine which parameter contains the Fqn in  
question, and we use the Fqn to determine the cache region and use  
the appropriate context class loader.  A bit hacky in the way the  
region is identified, but works well.

2)  Now for return values, there is no way to determine the region  
with which to attach the response value to, without changing the  
interface of the marshaller (which implements a JGroups interface) so  
the Region or Fqn or maybe even a ClassLoader is somehow passed in.

What I've done is that I've assumed that when objectFromByteBuffer()  
is called, you could safely assume that if the object that you  
recreate is NOT a MethodCall, then it is a return value.  If it is a  
MethodCall, we get a hold of the Fqn (see (1)) and put it in a  
ThreadLocal container.  This way, when the same thread calls  
objectToByteBuffer() to marshall a return value, it will have a  
handle on the Fqn and hence the class loader.

Like I said, this is a bit hacky and only really works for RPC based  
use of the marshaller to deal with return values of method calls.

I don't think this is a problem for other uses of the marshaller like  
State Transfer and cache loaders since it is not used in an RPC  
context, but I just thought I'd post this here in case someone feels  
like proving me wrong.  :-)

Cheers,
--
Manik Surtani

Lead, JBoss Cache
JBoss, a division of Red Hat

Email: manik at jboss.org
Telephone: +44 7786 702 706
MSN: manik at surtani.org
Yahoo/AIM/Skype: maniksurtani