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<?php
/**
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
*/
namespace MediaWiki\Sparql;
use Http;
use MediaWiki\Http\HttpRequestFactory;
/**
* Simple SPARQL client
*
* @author Stas Malyshev
*/
class SparqlClient {
/**
* Limit on how long can be the query to be sent by GET.
*/
const MAX_GET_SIZE = 2048;
/**
* User agent for HTTP requests.
* @var string
*/
private $userAgent;
/**
* Query timeout (seconds)
* @var int
*/
private $timeout = 30;
/**
* SPARQL endpoint URL
* @var string
*/
private $endpoint;
/**
* Client options
* @var array
*/
private $options = [];
/**
* @var HttpRequestFactory
*/
private $requestFactory;
/**
* @param string $url SPARQL Endpoint
* @param HttpRequestFactory $requestFactory
*/
public function __construct( $url, HttpRequestFactory $requestFactory ) {
$this->endpoint = $url;
$this->requestFactory = $requestFactory;
$this->userAgent = Http::userAgent() . " SparqlClient";
}
/**
* Set query timeout (in seconds)
* @param int $timeout
* @return $this
*/
public function setTimeout( $timeout ) {
if ( $timeout >= 0 ) {
$this->timeout = $timeout;
}
return $this;
}
/**
* Set client options
* @param array $options
* @return $this
*/
public function setClientOptions( $options ) {
$this->options = $options;
return $this;
}
/**
* Get current user agent.
* @return string
*/
public function getUserAgent() {
return $this->userAgent;
}
/**
* Set user agent string.
*
* Mote it is not recommended to completely override user agent for
* most applications.
* @see appendUserAgent() for recommended way of specifying user agent.
*
* @param string $agent
*/
public function setUserAgent( $agent ) {
$this->userAgent = $agent;
}
/**
* Append specific string to user agent.
*
* This is the recommended way of specifying the user agent
* for specific applications of the SparqlClient inside MediaWiki
* and extension code.
*
* @param string $agent
*/
public function appendUserAgent( $agent ) {
$this->userAgent .= ' ' . $agent;
}
/**
* Query SPARQL endpoint
*
* @param string $sparql query
* @param bool $rawData Whether to return only values or full data objects
*
* @return array List of results, one row per array element
* Each row will contain fields indexed by variable name.
* @throws SparqlException
*/
public function query( $sparql, $rawData = false ) {
if ( empty( $this->endpoint ) ) {
throw new SparqlException( 'Endpoint URL can not be empty' );
}
$queryData = [ "query" => $sparql, "format" => "json" ];
$options = array_merge( [ 'method' => 'GET' ], $this->options );
if ( empty( $options['userAgent'] ) ) {
$options['userAgent'] = $this->userAgent;
}
if ( $this->timeout >= 0 ) {
// Blazegraph setting, see https://wiki.blazegraph.com/wiki/index.php/REST_API
$queryData['maxQueryTimeMillis'] = $this->timeout * 1000;
$options['timeout'] = $this->timeout;
}
if ( strlen( $sparql ) > self::MAX_GET_SIZE ) {
// big requests go to POST
$options['method'] = 'POST';
$options['postData'] = 'query=' . urlencode( $sparql );
unset( $queryData['query'] );
}
$url = wfAppendQuery( $this->endpoint, $queryData );
$request = $this->requestFactory->create( $url, $options, __METHOD__ );
$status = $request->execute();
if ( !$status->isOK() ) {
throw new SparqlException( "HTTP error: {$status->getWikiText()}" );
}
$result = $request->getContent();
\Wikimedia\suppressWarnings();
$data = json_decode( $result, true );
\Wikimedia\restoreWarnings();
if ( $data === null || $data === false ) {
throw new SparqlException( "HTTP request failed, response:\n" .
substr( $result, 1024 ) );
}
return $this->extractData( $data, $rawData );
}
/**
* Extract data from SPARQL response format.
* The response must be in format described in:
* https://www.w3.org/TR/sparql11-results-json/
*
* @param array $data SPARQL result
* @param bool $rawData Whether to return only values or full data objects
*
* @return array List of results, one row per element.
*/
private function extractData( $data, $rawData = false ) {
$result = [];
if ( $data && !empty( $data['results'] ) ) {
$vars = $data['head']['vars'];
$resrow = [];
foreach ( $data['results']['bindings'] as $row ) {
foreach ( $vars as $var ) {
if ( !isset( $row[$var] ) ) {
$resrow[$var] = null;
continue;
}
if ( $rawData ) {
$resrow[$var] = $row[$var];
} else {
$resrow[$var] = $row[$var]['value'];
}
}
$result[] = $resrow;
}
}
return $result;
}
}
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