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https://issues.apache.org/jira/browse/LUCENE-4713?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Christian Kohlschütter updated LUCENE-4713:
-------------------------------------------
Description:
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.
was:
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.
> 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
> Attachments: 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.
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