/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.stanbol.entityhub.site.linkeddata.impl;
import java.io.IOException;
import java.io.InputStream;
import org.apache.clerezza.rdf.core.MGraph;
import org.apache.clerezza.rdf.core.UriRef;
import org.apache.clerezza.rdf.core.impl.SimpleMGraph;
import org.apache.clerezza.rdf.core.serializedform.Parser;
import org.apache.clerezza.rdf.core.serializedform.SupportedFormat;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.ConfigurationPolicy;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.Service;
import org.apache.stanbol.commons.indexedgraph.IndexedMGraph;
import org.apache.stanbol.entityhub.core.site.AbstractEntityDereferencer;
import org.apache.stanbol.entityhub.model.clerezza.RdfValueFactory;
import org.apache.stanbol.entityhub.servicesapi.model.Representation;
import org.apache.stanbol.entityhub.servicesapi.site.EntityDereferencer;
import org.slf4j.LoggerFactory;
/**
*
* @author Rupert Westenthaler
*
*/
@Component(
name="org.apache.stanbol.entityhub.dereferencer.SparqlDereferencer",
factory="org.apache.stanbol.entityhub.dereferencer.SparqlDereferencerFactory",
policy=ConfigurationPolicy.REQUIRE, //the baseUri and the SPARQL Endpoint are required
specVersion="1.1"
)
@Service(value=EntityDereferencer.class)
public class SparqlDereferencer extends AbstractEntityDereferencer {
private final RdfValueFactory valueFactory = RdfValueFactory.getInstance();
public SparqlDereferencer(){
super(LoggerFactory.getLogger(SparqlDereferencer.class));
}
@Reference
private Parser parser;
/*
* TODO: Supports only Triple serialisations as content types.
* To support other types one would need to create a select query and
* format the output accordingly.
* However it is not clear if such a functionality is needed.
*/
@Override
public final InputStream dereference(String uri, String contentType) throws IOException {
if(uri==null){
return null;
}
UriRef reference = new UriRef(uri);
StringBuilder query = new StringBuilder();
query.append("CONSTRUCT { ");
query.append(reference);
query.append(" ?p ?o } WHERE { ");
query.append(reference);
query.append(" ?p ?o }");
//String format = SupportedFormat.RDF_XML;
return SparqlEndpointUtils.sendSparqlRequest(getAccessUri(),query.toString(),contentType);
}
public final Representation dereference(String uri) throws IOException {
long start = System.currentTimeMillis();
String format = SupportedFormat.RDF_XML;
InputStream in = dereference(uri, format);
long queryEnd = System.currentTimeMillis();
log.info(" > DereferenceTime: "+(queryEnd-start));
if(in != null){
MGraph rdfData = new IndexedMGraph(parser.parse(in, format,new UriRef(getBaseUri())));
long parseEnd = System.currentTimeMillis();
log.info(" > ParseTime: "+(parseEnd-queryEnd));
return valueFactory.createRdfRepresentation(new UriRef(uri), rdfData);
} else {
return null;
}
}
// /**
// * We need also to check for the endpointURI of the SPARQL service. So override
// * the default implementation and check for the additional property!
// */
// @Activate
// @Override
// public void activate(ComponentContext context) {
// //super config
// super.activate(context);
// log.info(" init sparql endpoint property");
// }
// @Deactivate
// @Override
// protected void deactivate(ComponentContext context) {
// super.deactivate(context);
// }
}