[
https://issues.apache.org/jira/browse/LUCENE-4713?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13599927#comment-13599927
]
Uwe Schindler edited comment on LUCENE-4713 at 3/12/13 11:44 AM:
-----------------------------------------------------------------
There is another problem: The abstract clazz' classloader may be null, too
(although this never happens in recent JDKs): The bootstrap class loader may be
null. But we don't have the problem here, as Lucene classes are never ever
loaded through the boot class loader (but e.g. String.class.getClassLoader()
may return null).
I dont like hooking also into reload(), I will think of another more elegant
solution). -But to mention: If the context class loader is null (which cannot
happen unless you explicitly set it to null), Java's own classloading for SPIs
would be broken, too (see the implementation of java.util.ServiceLoader).-
(EDIT: Java's ServiceLoader uses SystemClassLoader if context loader is null)
was (Author: thetaphi):
There is another problem: The abstract clazz' classloader may be null, too
(although this never happens in recent JDKs): The bootstrap class loader may be
null. But we don't have the problem here, as Lucene classes are never ever
loaded through the boot class loader (but e.g. String.class.getClassLoader()
may return null).
I dont like hooking also into reload(), I will think of another more elegant
solution). But to mention: If the context class loader is null (which cannot
happen unless you explicitly set it to null), Java's own classloading for SPIs
ould be broken, too (see the implementation of java.util.ServiceLoader).
> SPI: Allow fallback to default ClassLoader if Thread#getContextClassLoader
> fails
> --------------------------------------------------------------------------------
>
> Key: LUCENE-4713
> URL: https://issues.apache.org/jira/browse/LUCENE-4713
> Project: Lucene - Core
> Issue Type: Improvement
> Affects Versions: 4.0, 4.1, 4.2
> Reporter: Christian Kohlschütter
> Assignee: Uwe Schindler
> Priority: Minor
> Labels: ClassLoader, Thread
> Fix For: 4.3
>
> Attachments: LUCENE-4713.patch, LUCENE-4713.patch, LUCENE-4713.patch,
> LUCENE-4713.patch, LUCENE-4713.patch, LUCENE-4713.patch,
> LuceneContextClassLoader.patch
>
>
> NOTE: This issue has been renamed from:
> "Replace calls to Thread#getContextClassLoader with the ClassLoader of the
> current class"
> because the revised patch provides a clean fallback path.
> I am not sure whether it is a design decision or if we can indeed consider
> this a bug:
> In core and analysis-common some classes provide on-demand class loading
> using SPI. In NamedSPILoader, SPIClassIterator, ClasspathResourceLoader and
> AnalysisSPILoader there are constructors that use the Thread's context
> ClassLoader by default whenever no particular other ClassLoader was specified.
> Unfortunately this does not work as expected when the Thread's ClassLoader
> can't see the required classes that are instantiated downstream with the help
> of Class.forName (e.g., Codecs, Analyzers, etc.).
> That's what happened to us here. We currently experiment with running Lucene
> 2.9 and 4.x in one JVM, both being separated by custom ClassLoaders, each
> seeing only the corresponding Lucene version and the upstream classpath.
> While NamedSPILoader and company get successfully loaded by our custom
> ClassLoader, their instantiation fails because our Thread's
> Context-ClassLoader cannot find the additionally required classes.
> We could probably work-around this by using Thread#setContextClassLoader at
> construction time (and quickly reverting back afterwards), but I have the
> impression this might just hide the actual problem and cause further trouble
> when lazy-loading classes later on, and potentially from another Thread.
> Removing the call to Thread#getContextClassLoader would also align with the
> behavior of AttributeSource.DEFAULT_ATTRIBUTE_FACTORY, which in fact uses
> Attribute#getClass().getClassLoader() instead.
> A simple patch is attached. All tests pass.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira
---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscr...@lucene.apache.org
For additional commands, e-mail: dev-h...@lucene.apache.org
