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https://issues.apache.org/jira/browse/SOLR-5526?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Nikolay Khitrin updated SOLR-5526:
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Attachment: SOLR-5526.patch
I've attached patch where all static variables from {{QParserPlugin}} were
moved to inner static final class {{QParserPlugin.Defaults}}.
> Query parser extends standard cause NPE on Solr startup
> -------------------------------------------------------
>
> Key: SOLR-5526
> URL: https://issues.apache.org/jira/browse/SOLR-5526
> Project: Solr
> Issue Type: Bug
> Components: query parsers
> Affects Versions: 4.5.1, 4.6, 5.0
> Environment: Linux, Java 1.7.0_45
> Reporter: Nikolay Khitrin
> Priority: Blocker
> Attachments: SOLR-5526.patch
>
>
> Adding any custom query parser extending standard one with non-final field
> {{NAME}} lead to messy {{NullPointerException}} during Solr startup.
> Definition of standard parsers is located in
> {{QParserPlugin.standardPlugins}} static array. The array contains names from
> static {{NAME}} fields and classes for each plugin.
> But all of listed parsers are derived from {{QParserPlugin}}, so we have
> circular dependency of static fields.
> Normally, class loader start initializing {{QParserPlugin}} before all listed
> plugins in {{SolrCore.initQParsers}}, and array elements referenced to
> {{NAME}} plugins' fields are filled properly.
> Custom parsers are instantiated before standard parsers. And when we subclass
> plugin with non-final {{NAME}} field and add it to Solr via
> {{solrconfig.xml}}, class loader start loading our class before
> {{QParserPlugin}}. Because {{QParserPlugin}} is a superclass for plugin, it
> must be initialized before subclasses, and static dereferencing cause null
> elements in {{standardPlugins}} array because it filled before {{NAME}} field
> of loading plugin's superclass.
> How to reproduce:
> # Checkout Solr (trunk or stable)
> # Add the following line to solr/example/solr/collection1/conf/solrconfig.xml
> {{<queryParser name="fail" class="solr.search.LuceneQParserPlugin"/>}}
> # Call ant run-example in solr folder
> Possible workarounds:
> * dev-workaround: add {{int workaround =
> QParserPlugin.standardPlugins.length;}} as a first line to
> {{SolrCore.initQParsers}}
> * user-workaround: add plugin with final {{NAME}} field (edismax) to
> solrconfig.xml before subclasses of standard plugins.
> {{<queryParser name="workaround"
> class="solr.search.ExtendedDismaxQParserPlugin"/>}}
>
> Possible fix:
> Move {{standardPlugins}} to new final class to break circular dependency.
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