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* 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 arq.examples;
// The ARQ application API.
import org.apache.jena.atlas.io.IndentedWriter ;
import com.hp.hpl.jena.query.Query ;
import com.hp.hpl.jena.query.QueryExecution ;
import com.hp.hpl.jena.query.QueryExecutionFactory ;
import com.hp.hpl.jena.query.QueryFactory ;
import com.hp.hpl.jena.query.QuerySolution ;
import com.hp.hpl.jena.query.ResultSet ;
import com.hp.hpl.jena.rdf.model.Literal ;
import com.hp.hpl.jena.rdf.model.Model ;
import com.hp.hpl.jena.rdf.model.ModelFactory ;
import com.hp.hpl.jena.rdf.model.RDFNode ;
import com.hp.hpl.jena.rdf.model.Resource ;
import com.hp.hpl.jena.vocabulary.DC ;
/** Example 1 : Execute a simple SELECT query on a model
* to find the DC titles contained in a model. */
public class Ex1
{
static public final String NL = System.getProperty("line.separator") ;
public static void main(String[] args)
{
// Create the data.
// This wil be the background (unnamed) graph in the dataset.
Model model = createModel() ;
// First part or the query string
String prolog = "PREFIX dc: <"+DC.getURI()+">" ;
// Query string.
String queryString = prolog + NL +
"SELECT ?title WHERE {?x dc:title ?title}" ;
Query query = QueryFactory.create(queryString) ;
// Print with line numbers
query.serialize(new IndentedWriter(System.out,true)) ;
System.out.println() ;
// Create a single execution of this query, apply to a model
// which is wrapped up as a Dataset
QueryExecution qexec = QueryExecutionFactory.create(query, model) ;
// Or QueryExecutionFactory.create(queryString, model) ;
System.out.println("Titles: ") ;
try {
// Assumption: it's a SELECT query.
ResultSet rs = qexec.execSelect() ;
// The order of results is undefined.
for ( ; rs.hasNext() ; )
{
QuerySolution rb = rs.nextSolution() ;
// Get title - variable names do not include the '?' (or '$')
RDFNode x = rb.get("title") ;
// Check the type of the result value
if ( x.isLiteral() )
{
Literal titleStr = (Literal)x ;
System.out.println(" "+titleStr) ;
}
else
System.out.println("Strange - not a literal: "+x) ;
}
}
finally
{
// QueryExecution objects should be closed to free any system resources
qexec.close() ;
}
}
public static Model createModel()
{
Model m = ModelFactory.createDefaultModel() ;
Resource r1 = m.createResource("http://example.org/book#1") ;
Resource r2 = m.createResource("http://example.org/book#2") ;
r1.addProperty(DC.title, "SPARQL - the book")
.addProperty(DC.description, "A book about SPARQL") ;
r2.addProperty(DC.title, "Advanced techniques for SPARQL") ;
return m ;
}
}