[
https://issues.apache.org/jira/browse/LUCENE-4713?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13599912#comment-13599912
]
Uwe Schindler commented on LUCENE-4713:
---------------------------------------
bq. Regarding overriding Lucene's default codec implementations: We anyways
have to place any other modified, non-SPI Lucene classes in the same
ClassLoader, so I really appreciate that this patch enforces this.
Overriding default Lucene Codecs doesn't need to necessarily use the same class
name. Codecs are identified by their "name" as written into the index files
(e.g., "Lucene42"). If you implement another subclass of Codec with the same
name, but different class name, it is also taken into account. But in any case,
the class file must be listed before the lucene-core.jar one in classpath (btw,
this is used in Lucene 4.x, to allow a READ/WRITE variant of the Lucene3x codec
for testing only. The test-framework.jar simply exposes another class,
extending the original READONLY Lucene3x codec to support WRITE, but makeing it
available also with the "Lucene3x" name to the loader).
> 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
> Priority: Minor
> Labels: ClassLoader, Thread
> Fix For: 4.3
>
> Attachments: 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: [email protected]
For additional commands, e-mail: [email protected]
