{"id":1859,"date":"2021-05-31T05:54:54","date_gmt":"2021-05-31T05:54:54","guid":{"rendered":"https:\/\/www.aeologic.com\/blog\/?p=1859"},"modified":"2021-05-31T05:54:54","modified_gmt":"2021-05-31T05:54:54","slug":"requesthandlers-and-searchcomponents-in-solrconfig-ultimate-solr-guide","status":"publish","type":"post","link":"https:\/\/www.aeologic.com\/blog\/requesthandlers-and-searchcomponents-in-solrconfig-ultimate-solr-guide\/","title":{"rendered":"RequestHandlers and SearchComponents in SolrConfig \u2013 Ultimate Solr Guide"},"content":{"rendered":"
After the\u00a0<query><\/code>\u00a0section of\u00a0solrconfig.xml<\/code>, request handlers and search components are configured.A\u00a0request handler<\/em>\u00a0processes requests coming to Solr. These might be query requests or index update requests. You will likely need several of these defined, depending on how you want Solr to handle the various requests you will make.A\u00a0search component<\/em>\u00a0is a feature of search, such as highlighting or faceting. The search component is defined in\u00a0solrconfig.xml<\/code>\u00a0separate from the request handlers, and then registered with a request handler as needed.These are often referred to as “requestHandler” and “searchComponent”, which is how they are defined in\u00a0solrconfig.xml<\/code>.<\/section>\n
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Request Handlers<\/h2>\n

Every request handler is defined with a name and a class. The name of the request handler is referenced with the request to Solr, typically as a path. For example, if Solr is installed at\u00a0http:\/\/localhost:8983\/solr\/<\/code>\u00a0and you have a collection named “gettingstarted”, you can make a request that looks like this:<\/p>\n

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<\/code><\/pre>\n
http:\/\/localhost:8983\/solr\/gettingstarted\/select?q=solr<\/code><\/pre>\n
<\/code><\/pre>\n<\/div>\n
This query will be processed by the request handler with the name\u00a0\/select<\/code>. We\u2019ve only used the “q” parameter here, which includes our query term, a simple keyword of “solr”. If the request handler has more parameters defined, those will be used with any query we send to this request handler unless they are over-ridden by the client (or user) in the query itself.<\/p>\n
If you have another request handler defined, you would send your request with that name. For example,\u00a0\/update<\/code>\u00a0is a request handler that handles index updates (i.e., sending new documents to the index). By default,\u00a0\/select<\/code>\u00a0is a request handler that handles query requests.<\/p>\n
Request handlers can also process requests for nested paths of their names, for example, a request using\u00a0\/myhandler\/extrapath<\/code>\u00a0may be processed by a request handler registered with the name\u00a0\/myhandler<\/code>. If a request handler is explicitly defined by the name\u00a0\/myhandler\/extrapath<\/code>, that would take precedence over the nested path. This assumes you are using the request handler classes included with Solr; if you create your own request handler, you should make sure it includes the ability to handle nested paths if you want to use them with your custom request handler.<\/p>\n
It is also possible to configure defaults for request handlers with a section called\u00a0initParams<\/code>. These defaults can be used when you want to have common properties that will be used by each separate handler. For example, if you intend to create several request handlers that will all request the same list of fields in the response, you can configure an\u00a0initParams<\/code>\u00a0section with your list of fields. For more information about\u00a0initParams<\/code>, see the section\u00a0InitParams in SolrConfig<\/a>.<\/p>\n
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SearchHandlers<\/h3>\n
The primary request handler defined with Solr by default is the “SearchHandler”, which handles search queries. The request handler is defined, and then a list of defaults for the handler are defined with a\u00a0defaults<\/code>\u00a0list.<\/p>\n
For example, in the default\u00a0solrconfig.xml<\/code>, the first request handler defined looks like this:<\/p>\n
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<\/code><\/pre>\n
<requestHandler name=\"\/select\" class=\"solr.SearchHandler\">\r\n  <lst name=\"defaults\">\r\n    <str name=\"echoParams\">explicit<\/str>\r\n    <int name=\"rows\">10<\/int>\r\n  <\/lst>\r\n<\/requestHandler><\/code><\/pre>\n
<\/code><\/pre>\n<\/div>\n
This example defines the\u00a0rows<\/code>\u00a0parameter, which defines how many search results to return, to “10”. The\u00a0echoParams<\/code>\u00a0parameter defines that the parameters defined in the query should be returned when debug information is returned. Note also that the way the defaults are defined in the list varies if the parameter is a string, an integer, or another type.<\/p>\n
All of the parameters described in the section\u00a0Searching<\/a>\u00a0can be defined as defaults for any of the SearchHandlers.<\/p>\n
Besides\u00a0defaults<\/code>, there are other options for the SearchHandler, which are:<\/p>\n
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