/*
* 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 java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.apache.clerezza.rdf.core.MGraph;
import org.apache.clerezza.rdf.core.TripleCollection;
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.commons.io.IOUtils;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.ConfigurationPolicy;
import org.apache.felix.scr.annotations.Reference;
import org.apache.stanbol.commons.indexedgraph.IndexedMGraph;
import org.apache.stanbol.entityhub.core.query.QueryResultListImpl;
import org.apache.stanbol.entityhub.core.site.AbstractEntitySearcher;
import org.apache.stanbol.entityhub.query.clerezza.RdfQueryResultList;
import org.apache.stanbol.entityhub.query.clerezza.SparqlFieldQuery;
import org.apache.stanbol.entityhub.query.clerezza.SparqlFieldQueryFactory;
import org.apache.stanbol.entityhub.servicesapi.defaults.NamespaceEnum;
import org.apache.stanbol.entityhub.servicesapi.model.Representation;
import org.apache.stanbol.entityhub.servicesapi.query.FieldQuery;
import org.apache.stanbol.entityhub.servicesapi.query.QueryResultList;
import org.apache.stanbol.entityhub.servicesapi.site.EntitySearcher;
import org.codehaus.jettison.json.JSONArray;
import org.codehaus.jettison.json.JSONException;
import org.codehaus.jettison.json.JSONObject;
import org.slf4j.LoggerFactory;
@Component(
name="org.apache.stanbol.entityhub.searcher.SparqlSearcher",
factory="org.apache.stanbol.entityhub.searcher.SparqlSearcherFactory",
policy=ConfigurationPolicy.REQUIRE, //the queryUri and the SPARQL Endpoint are required
specVersion="1.1"
)
public class SparqlSearcher extends AbstractEntitySearcher implements EntitySearcher {
public SparqlSearcher() {
super(LoggerFactory.getLogger(SparqlSearcher.class));
}
@Reference
private Parser parser;
protected static final String DEFAULT_RDF_CONTENT_TYPE = SupportedFormat.RDF_XML;
protected static final String DEFAULT_SPARQL_RESULT_CONTENT_TYPE = SparqlEndpointUtils.SPARQL_RESULT_JSON;
@Override
public final QueryResultList<String> findEntities(FieldQuery parsedQuery) throws IOException {
final SparqlFieldQuery query = SparqlFieldQueryFactory.getSparqlFieldQuery(parsedQuery);
String sparqlQuery = query.toSparqlSelect(false);
InputStream in = SparqlEndpointUtils.sendSparqlRequest(getQueryUri(), sparqlQuery, DEFAULT_SPARQL_RESULT_CONTENT_TYPE);
//Move to util class!
final List<String> entities = extractEntitiesFromJsonResult(in,query.getRootVariableName());
return new QueryResultListImpl<String>(query, entities.iterator(),String.class);
}
/**
* Extracts the values of the Query. Also used by {@link VirtuosoSearcher}
* and {@link LarqSearcher}
* @param rootVariable the name of the variable to extract
* @param in the input stream with the data
* @return the extracted results
* @throws IOException if the input streams decides to explode
*/
protected static List<String> extractEntitiesFromJsonResult(InputStream in, final String rootVariable) throws IOException {
final List<String> entities;
try {
JSONObject result = new JSONObject(IOUtils.toString(in));
JSONObject results = result.getJSONObject("results");
if(results != null){
JSONArray bindings = results.getJSONArray("bindings");
if(bindings != null && bindings.length()>0){
entities = new ArrayList<String>(bindings.length());
for(int i=0;i<bindings.length();i++){
JSONObject solution = bindings.getJSONObject(i);
if(solution != null){
JSONObject rootVar = solution.getJSONObject(rootVariable);
if(rootVar != null){
String entityId = rootVar.getString("value");
if(entityId != null){
entities.add(entityId);
} //else missing value (very unlikely)
} //else missing binding for rootVar (very unlikely)
} //else solution in array is null (very unlikely)
} //end for all solutions
} else {
entities = Collections.emptyList();
}
} else {
entities = Collections.emptyList();
}
} catch (JSONException e) {
//TODO: convert in better exception
throw new IOException("Unable to parse JSON Result Set for parsed query",e);
}
return entities;
}
@Override
public final QueryResultList<Representation> find(FieldQuery parsedQuery) throws IOException{
long start = System.currentTimeMillis();
final SparqlFieldQuery query = SparqlFieldQueryFactory.getSparqlFieldQuery(parsedQuery);
String sparqlQuery = query.toSparqlConstruct();
long initEnd = System.currentTimeMillis();
log.info(" > InitTime: "+(initEnd-start));
log.info(" > SPARQL query:\n"+sparqlQuery);
InputStream in = SparqlEndpointUtils.sendSparqlRequest(getQueryUri(), sparqlQuery, DEFAULT_RDF_CONTENT_TYPE);
long queryEnd = System.currentTimeMillis();
log.info(" > QueryTime: "+(queryEnd-initEnd));
if(in != null){
MGraph graph;
TripleCollection rdfData = parser.parse(in, DEFAULT_RDF_CONTENT_TYPE,
new UriRef(getBaseUri()));
if(rdfData instanceof MGraph){
graph = (MGraph) rdfData;
} else {
graph = new IndexedMGraph(rdfData);
}
long parseEnd = System.currentTimeMillis();
log.info(" > ParseTime: "+(parseEnd-queryEnd));
return new RdfQueryResultList(query, graph);
} else {
return null;
}
}
}