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From David Jencks <david_jen...@yahoo.com>
Subject Re: Converting classloaders to BundleContexts
Date Tue, 20 Oct 2009 16:32:49 GMT

On Oct 20, 2009, at 8:29 AM, Jarek Gawor wrote:

> Actually, I think that we should restore the loadGBean(GBeanData,
> ClassLoader) method and use BundleReference to get the Bundle for the
> classloader. It would probably get things going a bit more and
> probably just work in most cases. If it doesn't work then we can come
> in and change the API to add additional methods to get the Bundle.

I haven't found that modifying gbean code to use Bundle instead of  
ClassLoader for classloading is a significant amount of work.  IMO if  
we are going to orient ourselves towards osgi we should use the osgi  
conventions wherever they are reasonably easy to adapt to.  This case  
is certainly one of them.

thanks
david jencks

>
> Jarek
>
> On Tue, Oct 20, 2009 at 7:58 AM, Rick McGuire <rickmcg@gmail.com>  
> wrote:
>> I just started taking a look at converting the Tomcat plugon to the  
>> brave
>> new OSGi world, and immediately ran into a problem that's likely to  
>> be a
>> fairly generic problem that other plugins might also have.  In the  
>> method
>> TomcatManagerImpl.getConnectorConfiguration(), there's the  
>> following code
>> that causes a compilation error:
>>
>>       try {
>>           kernel.loadGBean(gbeanData,
>> container.getClass().getClassLoader());
>>           kernel.startGBean(name);
>>       } catch (Exception e) {
>>           log.error("Error when adding new tomcat connector" +  
>> uniqueName,
>> e);
>>       }
>>
>>
>> the loadGBean() method now takes a BundleContext rather than a  
>> classloader,
>> so there's a signature error.  The container is an object that  
>> implements
>> the WebContainer interface (either the Tomcat or Jetty version).   
>> The intent
>> here is to load some GBeans using the container object's  
>> configuration
>> context via its classloader.  In order for this to work now,
>> getConnectorConfiguration() will need to somehow obtain the  
>> container's
>> BundleContext rather than a class loader.  This is something that's  
>> not
>> easily done at the moment.  I see a couple of potential solutions:
>>
>> 1)  Make the WebContainers context aware and add a  
>> getBundleContext() method
>> to the WebContainer interface. 2)  Use the BundleReference interface
>> introduced in the 4.2 OSGi framework to obtain the bundle from the  
>> object's
>> defining classloader.
>>
>> I suspect that 1) is the cleaner solution.  2) has a potential  
>> downside that
>> it depends on the WebContainer implementation class being located  
>> within
>> configuration bundle.  A restructuring of the bundles to improve  
>> modularity
>> could potentially cause this to fail, which would not really be a  
>> solid
>> structure.
>>
>> I think I've convinced myself that 1) is the correct approach, but  
>> thought
>> this was something worthing of raising as a discussion point on the  
>> dev
>> list.
>>
>> Rick
>>


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