Differences between revisions 26 and 27
Revision 26 as of 2008-10-30 16:25:42
Size: 13226
Editor: 226
Comment: Note that you can use a custom query parser without registering a search handler
Revision 27 as of 2008-11-05 17:15:36
Size: 13379
Editor: 226
Comment: Note "pluggable query parser" notation for q param
Deletions are marked like this. Additions are marked like this.
Line 70: Line 70:
You can also specify your query parser as part of the q parameter, like this:

Solr Plugins

Solr allows you to load custom code to perform a variety of tasks within Solr -- from custom Request Handlers to process your searches, to custom Analyzers and Token Filters for your text field, even custom Field Types. TableOfContents

How to Load Plugins

Plugin code can be loaded into Solr by putting Jars containing your classes in a lib directory in your Solr Home directory prior to starting your servlet container. In the example program, the location is example/solr/lib. This directory does not exist in the distribution, so you would need to do mkdir for the first time.

This feature for loading plugins uses a custom Class Loader. It has been tested with a variety of Servlet Containers, but given the multitudes of servlet containers available in the wild it may not always work with every servlet container.

The Old Way

Another method that works consistently on any servlet container is to:

  1. unpack the solr.war
  2. add a jar containing your custom classes to the WEB-INF/lib directory

  3. repack your new, customized, solr.war and use it.

Classes that are 'Pluggable'

The following is a complete list of every API that can be treated as a plugin in Solr, with information on how to use that configure your Solr instance to use an instance of that class.

Request Processing


Instances of [http://lucene.apache.org/solr/docs/api/org/apache/solr/request/SolrRequestHandler.html SolrRequestHandler] define the logic that is executed for any request. Multiple handlers (including multiple instances of the same SolrRequestHandler class with different configurations) can be specified in your [wiki:SolrConfigXml solrconfig.xml]...

  <requestHandler name="foo" class="my.package.CustomRequestHandler" />
  <requestHandler name="bar" class="my.package.AnotherCustomRequestHandler" />
  <requestHandler name="baz" class="my.package.AnotherCustomRequestHandler">
    <!-- initialization args may optionally be defined here -->
     <lst name="defaults">
       <int name="rows">10</int>
       <str name="fl">*</str>
       <str name="version">2.1</str>
     <int name="someConfigValue">42</int>

for more info, see: SolrRequestHandler


<!> ["Solr1.3"]

Instances of [http://lucene.apache.org/solr/api/org/apache/solr/handler/component/SearchComponent.html SearchComponent] define discrete units of logic that can be combined together and reused by Request Handlers that know about them. (in particular: [http://lucene.apache.org/solr/api/org/apache/solr/handler/component/SearchHandler.html SearchHandler])

for more info, see: SearchComponent


/!\ :TODO: /!\ NEED DOCS

[http://lucene.apache.org/solr/api/org/apache/solr/search/QParserPlugin.html QParserPlugin] can be used to define customized user query processing instances of [http://lucene.apache.org/solr/api/org/apache/solr/search/QParser.html QParser] .

First, implement a subclass of [http://lucene.apache.org/solr/api/org/apache/solr/search/QParserPlugin.html QParserPlugin] and register it in [wiki:SolrConfigXml solrconfig.xml] like this:

  <queryParser name="myqueryparser" class="my.package.MyQueryParserPlugin" />

Having done this, you can choose to use your query parser on a one-time basis using the defType query parameter, like this:


You can also specify your query parser as part of the q parameter, like this:


For more permanent use, you will likely want to define a separate SolrRequestHandler for your parser, like this:

   <requestHandler name="dismax" class="solr.SearchHandler" >
    <lst name="defaults">
     <str name="defType">myqueryparser</str>


/!\ :TODO: /!\ NEED DOCS


/!\ :TODO: /!\ NEED DOCS


/!\ :TODO: /!\ NEED DOCS


/!\ :TODO: /!\ NEED DOCS


/!\ :TODO: /!\ NEED DOCS


Instances of [http://lucene.apache.org/solr/docs/api/org/apache/solr/request/QueryResponseWriter.html QueryResponseWriter] define the formatting used to output the results of a request. Multiple writers (including multiple instances of the same QueryResponseWriter class with different configurations) can be specified in your [wiki:SolrConfigXml solrconfig.xml]...

  <queryResponseWriter name="wow" class="my.package.CustomResponseWriter" />
  <queryResponseWriter name="woz" class="my.package.AnotherCustomResponseWriter" />
  <queryResponseWriter name="woz" class="my.package.AnotherCustomResponseWriter" >
    <!-- initialization args may optionally be defined here -->
    <int name="someConfigValue">42</int>


The [http://lucene.apache.org/java/docs/api/org/apache/lucene/search/Similarity.html Similarity] class is a native Lucene concept that determines how much of the score calculations for the various types of queries are executed. For more information on how the methods in the Similarity class are used, consult the [http://lucene.apache.org/java/docs/scoring.html Lucene scoring documentation]. If you wish to override the DefaultSimilarity provided by Lucene, you can specify your own subclass in your [wiki:SchemaXml schema.xml]...

  <similarity class="my.package.CustomSimilarity"/>


The [http://lucene.apache.org/solr/docs/api/org/apache/solr/search/CacheRegenerator.html CacheRegenerator] API allows people who are writing custom SolrRequestHandlers which utilize custom [wiki:SolrCaching User Caches] to specify how those caches should be populated during autowarming. A regenerator class can be specified when the cache is declared in your [wiki:SolrConfigXml solrconfig.xml]...

    <cache name="myCustomCacheInstance"



The [http://lucene.apache.org/java/docs/api/org/apache/lucene/analysis/Analyzer.html Analyzer] class is a native Lucene concept that determines how tokens are produced from a piece of text. Solr allows Analyzers to be specified for each fieldtype in your [wiki:SchemaXml schema.xml] that uses the TextField class -- and even allows for different Analyzers to be specified for indexing text as documents are added, and parsing text specified in a query...

    <fieldtype name="text_foo" class="solr.TextField">
      <analyzer class="my.package.CustomAnalyzer"/>
    <fieldtype name="text_bar" class="solr.TextField">
      <analyzer type="index" class="my.package.CustomAnalyzerForIndexing"/>
      <analyzer type="query" class="my.package.CustomAnalyzerForQuering"/>

Solr also provides a [http://lucene.apache.org/solr/docs/api/org/apache/solr/analysis/SolrAnalyzer.html SolrAnalyzer] base class which can be used if you want to write your own Analyzer and configure the "positionIncrementGap" in your schema.xml...

    <fieldtype name="text_baz" class="solr.TextField" positionIncrementGap="100">
      <analyzer class="my.package.CustomSolrAnalyzer" />

Specifying an Analyzer class in your schema.xml makes a lot of sense if you already have an existing Analyzer you wish to use as is, but if you are planning to write Analysis code from scratch that you would like to use in Solr, you should keep reading the following sections...

Tokenizer and TokenFilter

In addition to specifing specific Analyzer classes, Solr can construct Analyzers on the fly for each field type using a [http://lucene.apache.org/java/docs/api/org/apache/lucene/analysis/Tokenizer.html Tokenizer] and any number of [http://lucene.apache.org/java/docs/api/org/apache/lucene/analysis/TokenFilter.html TokenFilters]. To take advantage of this functionality with any Tokenizers or TokenFilters you may have (or may want to implement) you'll need to provide a [http://lucene.apache.org/solr/docs/api/org/apache/solr/analysis/TokenizerFactory.html TokenizerFactory] and [http://lucene.apache.org/solr/docs/api/org/apache/solr/analysis/TokenFilterFactory.html TokenFilterFactory] which takes care of any initialization and configuration, and specify these Factories in your [wiki:SchemaXml schema.xml]...

    <fieldtype name="text_zop" class="solr.TextField" positionIncrementGap="100">
          <tokenizer class="my.package.CustomTokenizerFactory"/>
          <!-- this TokenFilterFactory has custom options -->
          <filter class="my.package.CustomTokenFilter" optA="yes" optB="maybe" optC="42.5"/>
          <!-- Solr has many existing FilterFactories that you can reuse -->
          <filter class="solr.StopFilterFactory" ignoreCase="true"/>


If you have very specialized data type needs, you can specify your own [http://lucene.apache.org/solr/docs/api/org/apache/solr/schema/FieldType.html FieldType] class for each <fieldtype> you declare in your [wiki:SchemaXml schema.xml], to control how the values for those fields are encoded in your index...

    <fieldtype name="wacko" class="my.package.CustomFieldType" />



The [http://lucene.apache.org/solr/docs/api/org/apache/solr/search/SolrCache.html SolrCache] API allows you to specify custom Cache implementations for any of the [wiki:SolrCaching various caches] you might declare in your [wiki:SolrConfigXml solrconfig.xml]...

    <filterCache       class="my.package.CustomCache"          size="512" />
    <queryResultsCache class="my.package.CustomCache"          size="512"  />
    <documentCache     class="my.package.AlternateCustomCache" size="512"  />


Instances of the [http://lucene.apache.org/solr/docs/api/org/apache/solr/core/SolrEventListener.html SolrEventListener] Interface can be configured in your [wiki:SolrConfigXml solrconfig.xml] to be be executed any time specific events occur within Solr (currently, the only events that can be "listened" for are firstSearcher and newSearcher)...

    <listener event="newSearcher" class="my.package.CustomEventListener">
      <-- init args for the EventListener instance can be specified here -->
      <lst name="arg1">
        <str name="q">solr</str> <str name="start">0</str> <str name="rows">10</str>
      <int name="otherArg">42</int>


The [http://lucene.apache.org/solr/docs/api/org/apache/solr/update/UpdateHandler.html UpdateHandler] API allows you to specify a custom algorithm for determining how sequences of adds and deletes are processed by Solr. The UpdateHandler you wish to use can be configured in your [wiki:SolrConfigXml solrconfig.xml], but implementing a new UpdateHandler is considered extremely advanced and is not recommended....

  <updateHandler class="my.package.CustomUpdateHandler">

Building Plugins

To develop your own plugins, add the apache-solr-*.jar jar files to the classpath you use to compile your code. They contains all of the Solr Interfaces and Class files you may need. If you are developing plugins that know about lower level Lucene interfaces, you may need to also include the lucene-*.jar jar files from the lib/ directory of your Solr distribution.

Plugin Initialization

<!> ["Solr1.3"]

Plugins are initializes either with [http://svn.apache.org/repos/asf/lucene/solr/trunk/src/java/org/apache/solr/util/plugin/MapInitializedPlugin.java init( Map<String,String> args )] or [http://svn.apache.org/repos/asf/lucene/solr/trunk/src/java/org/apache/solr/util/plugin/NamedListInitializedPlugin.java init( NamedList args )].


Classes that need to know about the [http://svn.apache.org/repos/asf/lucene/solr/trunk/src/java/org/apache/solr/common/ResourceLoader.java ResourceLoader] can implement [http://svn.apache.org/repos/asf/lucene/solr/trunk/src/java/org/apache/solr/util/plugin/ResourceLoaderAware.java ResourceLoaderAware]. Valid ResourceLoaderAware include:

  • TokenFilterFactory

  • TokenizerFactory

  • FieldType


Classes that need to know about the [SolrCore] can implement [http://svn.apache.org/repos/asf/lucene/solr/trunk/src/java/org/apache/solr/util/plugin/SolrCoreAware.java SolrCoreAware]. Valid SolrCoreAware classes include:


The initialization lifecycle is:

  1. Constructor
  2. init( Map / NamedList )

  3. ResourceLoaderAware classes call: inform( ResourceLoader );

  4. Before the first request is made and after all plugins have been created and registered, SolrCoreAware plugins call: inform( SolrCore );

SolrPlugins (last edited 2017-01-03 19:18:41 by ShawnHeisey)