[hibernate-dev] classloading issue when trying to add envers to as7

[Scott Marlow]

On 06/17/2011 07:22 AM, Steve Ebersole wrote:
> I remember Scott and I discussing this exact issue. Unfortunately I do
> not remember the specifics. java.util.ServiceLoader#load(Class<S>
> service) does use the TCCL, but I think that the end result of our
> discussion was this is ok.
>
> We need to have this call be able to locate services both within the
> module classloader as well as within the classloader that ikncludes the
> user app. Scott, is there a single classloader that covers both of those
> cases that we could use?

Basically, we need to inject any needed modules into the application.

>
> On 06/16/2011 06:54 AM, Strong Liu wrote:
>> Hi there,
>>
>> first of all, I have finished this task, and test pass.
>> but :), i have to make the following changes, i'd like to hear you
>> guys' thoughts before i go to much away.
>>
>> 1. adding envers into org.hibernate module in as7, so user's app can
>> see both hibernate and envers class
>> (with an separate envers module i ran into some cycle dependency issue)

Well, I forget what you did exactly Strong, but the above statement (1) 
sounds wrong.  It may be true but what you stated would not give the app 
classloader, access to the envers module.  Adding envers into the 
org.hibernate module, means that Hibernate code can load the envers 
classes.

Did you get a circular dependency error message?  Or are you just trying 
to design around possible cycles?



>>
>> 2. envers throws "listeners were not registed" exception, means
>> hibernate's IntegratorServiceImpl can't see envers class/resource
>>
>> IntegratorServiceImpl is using java.util.ServiceLoader#load(Class<S>
>> service), which internally using TCCL, (I think)
>> that's the reason why core can't see envers' integrator.
>>
>> so, i created a custom ServiceLoader which use ClassLoaderService to
>> find the integrator, but this doesn't work either.
>> since, we need
>> org.hibernate.service.classloading.internal.ClassLoaderServiceImpl#locateResources
>> first (META-INF/services/org.hibernate.integrator.spi.Integrator) and
>> ClassLoaderServiceImpl using resourceClassLoader to do this.
>> by default, resourceClassLoader is set to applicationClassLoader in
>> ClassLoaderServiceImpl.
>>
>> then, i changed IntegratorServiceImpl to use
>> java.util.ServiceLoader#load(Class<S> service,
>> IntegratorServiceImpl.class.getClassLoader()
>> ), test pass, but this of course is not the fix.
>>
>> so, i changed the custom ServiceLoader to use classLoaderService to
>> locateResources first, and using ServiceLoader.class.getClassLoader()
>> to reload the resource again.
>>
>> here are the changes:
>> https://github.com/stliu/hibernate-core/commit/09ce5defabea8cfb87d06c3d7b9bc1a2c613f62c
>>
>> https://github.com/stliu/jboss-as/commit/616237755626672157fb2ae565fadb16cf47af89
>>
>>
>> thoughts?
>>
>> -----------
>> Strong Liu<stliu at hibernate.org>
>> http://hibernate.org
>> http://github.com/stliu
>>
>