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Posted to dev@lucene.apache.org by "Hoss Man (JIRA)" <ji...@apache.org> on 2014/02/05 02:45:10 UTC
[jira] [Resolved] (SOLR-5526) Query parser extends standard cause
NPE on Solr startup
[ https://issues.apache.org/jira/browse/SOLR-5526?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Hoss Man resolved SOLR-5526.
----------------------------
Resolution: Fixed
Fix Version/s: 4.7
5.0
Thanks Nikolay & Vitaliy!
> 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
> Fix For: 5.0, 4.7
>
> Attachments: NPE_load_trace, SOLR-5526-final-names.patch, SOLR-5526-final-names.patch, SOLR-5526-tests.patch, SOLR-5526.patch, SOLR-5526.patch, SOLR-5526.patch, SOLR-5526.patch, 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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