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From "Richard S. Hall (JIRA)" <j...@apache.org>
Subject [jira] Commented: (FELIX-712) Ability to disable automatic parent classloader delegation
Date Fri, 19 Jun 2009 19:00:08 GMT

    [ https://issues.apache.org/jira/browse/FELIX-712?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12721936#action_12721936

Richard S. Hall commented on FELIX-712:

Is there any hope of getting a small example that demonstrates this? It seems like we should
be able to fix it.

> Ability to disable automatic parent classloader delegation
> ----------------------------------------------------------
>                 Key: FELIX-712
>                 URL: https://issues.apache.org/jira/browse/FELIX-712
>             Project: Felix
>          Issue Type: Improvement
>          Components: Framework
>    Affects Versions: felix-1.2.0
>            Reporter: Don Brown
>            Assignee: Karl Pauls
>         Attachments: delegate.patch
> In debugging a strange issue why a certain test was passing in IDEA, but failing in Maven,
we discovered that under certain conditions, Felix will delegate to the parent classloader
if it detects another class in the stack who's classloader differs from the classloader of
Felix. Specifically, in org.apache.felix.framework.searchpolicy.R4SearchPolicyCore starting
in line 541, there is the problematic code block that has this comment:
>        // At this point, the class/resource could not be found by the bundle's
>        // static or dynamic imports, nor its own content. Before we throw
>        // an exception, we will try to determine if the instigator of the
>        // class/resource load was a class from a bundle or not. This is necessary
>        // because the specification mandates that classes on the class path
>        // should be hidden (except for java.*), but it does allow for these
>        // classes/resources to be exposed by the system bundle as an export.
>        // However, in some situations classes on the class path make the faulty
>        // assumption that they can access everything on the class path from
>        // every other class loader that they come in contact with. This is
>        // not true if the class loader in question is from a bundle. Thus,
>        // this code tries to detect that situation. If the class
>        // instigating the load request was NOT from a bundle, then we will
>        // make the assumption that the caller actually wanted to use the
>        // parent class loader and we will delegate to it. If the class was
>        // from a bundle, then we will enforce strict class loading rules
>        // for the bundle and throw an exception.
> What that means is if if you call Bundle.loadClass() from a non-bundle class and you
happen to have a class in your stack, which was loaded from a different classloader than Felix,
Felix will try to fix your problem by allowing parent classloader delegation. This was the
cause of the breakage for us because Maven's Surefire plugin uses its own classloader to load
several of its classes and Felix found those in the call stack and decided to enable parent
delegation. In IDEA, all the classes were loaded by the same classloader, so our tests passed.
> Specifically, we have code that sits outside Felix and tries to load classes from installed
bundles.  Felix sees that the call, by examining the stack, is by code outside a bundle, so
it enters this routine that may or may not, depending on the execution environment, delegate
the class loading to Felix's class loader.  
> This ticket asks for a configuration setting to be able to disable this bit of code.

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