Client APIs

HTTP is the fundamental protocol used between client applications and Solr. The client makes a request and Solr does some work and provides a response. Clients use requests to ask Solr to do things like perform queries or index documents.

Client applications can reach Solr by creating HTTP requests and parsing the HTTP responses. Client APIs encapsulate much of the work of sending requests and parsing responses, which makes it much easier to write client applications.

Clients use Solr’s five fundamental operations to work with Solr. The operations are query, index, delete, commit, and optimize.

Queries are executed by creating a URL that contains all the query parameters. Solr examines the request URL, performs the query, and returns the results. The other operations are similar, although in certain cases the HTTP request is a POST operation and contains information beyond whatever is included in the request URL. An index operation, for example, may contain a document in the body of the request.

Solr also features an EmbeddedSolrServer that offers a Java API without requiring an HTTP connection. For details, see SolrJ.

Many programming environments are able to send HTTP requests and retrieve responses. Parsing the responses is a slightly more thorny problem. Fortunately, Solr makes it easy to choose an output format that will be easy to handle on the client side.

Specify a response format using the wt parameter in a query. The available response formats are documented in xref:query-guide:response-writers.adoc.

Most client APIs hide this detail for you, so for many types of client applications, you won’t ever have to specify a wt parameter. In JavaScript, however, the interface to Solr is a little closer to the metal, so you will need to add this parameter yourself.