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From "Richard S. Hall" <he...@ungoverned.org>
Subject Re: Fixed bug in class loading
Date Fri, 07 Apr 2006 14:00:27 GMT
John,

Yes, you have struck on an issue here, which is kind of ugly.

For the most part, this issue revolves around that fact that many of the 
libraries in the JRE make the assumption that they can get to the system 
class loader from any class loader they choose. For OSGi bundle class 
loaders, this is not true, since we don't delegate to the parent by default.

I have, however, implemented a hack in Felix that tries to check for 
some of these situations and properly delegate to the parent class 
loader, but it still doesn't not detect every situation...I just 
discovered one such situation two days ago with Swing.

You are correct that the boot delegation property will help us out here, 
because we can at least put problematic Sun implementation packages on 
it. I will try to find the time to implement this property in the next 
couple days...it should be pretty straight forward. I will post to the 
list and we will set the default value in config.properties to include 
these packages to you can remove them from your bundles.

I would also be interested in seeing small bundles that demonstrate the 
problem, so that I might be able to see if there are ways to improve my 
hack to detect this situation automatically.

Sorry for the pain...unfortunately, it is hard to be modular in a 
non-modular world. ;-)

-> richard


John E. Conlon wrote:
> Hello Richard,
>
> As you mentioned after the change I had to edit my bundle Import-Package
> headers to get bundles to resolve without NoClassDefFoundErrors. 
> Now the tough part about this was that I had to not only import all the
> javax classes I was using but also the sun, and even the com.sun
> packages in the imports as well.  Then I had to add the various
> javax.xxx, sun.xxx and com.sun.xxx packages to the config.properties
> file's org.osgi.framework.system.packages property as well.
>
> Now I must confess that reading the classloading part of the OSGi spec
> makes my eyes glaze over, but I did notice section 3.8.3 discussion of
> parent delegation. It talks about a bootdelegation property that can add
> packages to the parent classloader like this:
>
> property org.osgi.framework.bootdelegation=sun.*,com.sun.*
>
> Maybe I am paranoid but I feel uncomfortable doing anything (even
> declaring imports in bundles) with the sun and com.sun packages. Could
> the bootdelegation property eventually come to the rescue?
>
> cheers,
> John
>
> On Wed, 2006-04-05 at 04:54 -0400, Richard S. Hall wrote:
>   
>> Hello everyone,
>>
>> I just wanted to let you know that I discovered and fixed a bug in Felix 
>> class loading that was accidentally exposing classes on the class path 
>> to bundles, even if they did not import them.
>>
>> This bug was introduced during the module layer refactoring.
>>
>> I am posting a message about this to let people know that they should 
>> "svn update" and after they do, they might experience 
>> NoClassDefFoundErrors and the like if their bundles' manifests are 
>> incomplete. If you run into this situation, most likely, you just need 
>> to add the package to the Import-Package header of the bundle.
>>
>> -> richard
>>
>>     
>
>
>   

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