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https://issues.apache.org/jira/browse/LUCENE-7873?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Uwe Schindler resolved LUCENE-7873.
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Resolution: Fixed
> Remove context classloader from SPI lookups by default
> ------------------------------------------------------
>
> Key: LUCENE-7873
> URL: https://issues.apache.org/jira/browse/LUCENE-7873
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/other
> Reporter: Uwe Schindler
> Assignee: Uwe Schindler
> Priority: Critical
> Fix For: master (7.0)
>
> Attachments: LUCENE-7873.patch, LUCENE-7873.patch
>
>
> As discussed on LUCENE-7870, we should really remove the context class loader
> from Lucene's SPI lookup (NamedSPLoader, SPIClassIterator, AnalysisSPI stuff).
> {quote}
> My idea would be (as stated before): Get rid of the Context Classloader in
> SPI lookups! Lucene never uses it, it is just there for backwards
> compatibility. The current setup of SPI does not work with modules of Java 9
> and it does not work with stuff in completely different classloaders. So OSGI
> fails in any case, if you have lucene-core.jar and
> lucene-backwards-codecs.jar as OSGI modules, because both would use different
> loaders. The context loader won't help.
> The problem is that we may break some apps that rely on the context loader
> traversal. In my opinion, we may add a system property that is read on setup
> of NamedSPILoader / SPIClassIterator that can be set to true (e.g.
> lucene.useContextLoaderForSPI, defaulting to false). This may fix legacy apps
> and new apps would only traverse the classloader that loaded lucene-core.jar.
> For Java 9 and "Lucene as Java 9 module") we have to refactor this anyways,
> becaue we need to respect module-info,java and look for SPI exports.
> FYI: Context class loaders were the worst idea ever in Java. I personally
> hate them and I would do anything - just to make them disappear from the
> spec! When drinking beers with Mark Reinhold in Brussels, I am always
> reminding him about this together with the inability to unmap byte buffers...
> :-)
> {quote}
> Unfortunately the sysprop approach is the only way to handle this as this
> must be done very early on JVM/Lucene setup. If somebody called
> Codec.forName() its too late to change the default... But I am fine with
> using a sysprop with AccessController.doPrivileged(), as this is only
> required for those legacy WEBAPP stuff. Normal applications should see the
> META-INF files on the application classloader anyways.
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