[jboss-as7-dev] Module Compatible Classloading Guide

[Scott Marlow]

"In Java EE code, the TCCL is always the classloader of the relevant 
deployment".  How do/should our (toplevel) EE containers ensure that the 
TCCL is set to the deployment?  How do we turn a naked thread into a 
managed thread?

I'm a little confused about the following sentence (from section 
FRAMEWORKS, NEVER LOAD YOUR CLASSES FROM THE TCCL!!):

"If the defining classloader is not the right classloader, then pick it 
and use it to load classes."

One other concern about the frameworks section, applications are often 
providing their own frameworks and can hit the issues called out there 
(like hitting a brick wall).  It might be worth adding another section 
that raises the issues that applications will hit with any naked threads 
that they create (hopefully not from an EE thread).  As well as 
application code that also expects to use the AS7 infrastructure jars as 
they have in the past.

About "What To Export/Expose", I'm thinking about how I abused this rule 
with the "org.hibernate" module (I'm still wondering if I should abuse 
this rule further by including more of the Hibernate jars that 
applications might want access to in the future).  Some of the other 
Hibernate jars might be accessed through the EntityManager.unwrap(Class) 
feature (that is being discussed anyway).  Also, it might be nice to 
call out how the as7/build/build.xml (module-def) contains the exact 
list of the jars copied into the particular module.  As well as the 
magic that happens behind the scenes, when a module dependency is exported.

About "How to deal with "Bad" dependencies".  Maybe rename to "How to 
deal with CNFE caused by code that would of caused Jar hell problems if 
we didn't make you jump through hoops to fix".  ;)  Okay, my title 
suggestion isn't much better.

Thanks,
Scott

On 04/07/2011 01:33 PM, Jason T. Greene wrote:
> I created an initial version of a guide on how to use class loading
> correctly in a modular classloading environment like in AS7.
>
> Everyone that is writing AS7 code should review it. If you have any
> questions ask and I will clarify it in the document.
>
> http://community.jboss.org/wiki/ModuleCompatibleClassloadingGuide
>