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  • VOS.VirtJenaSPARQLExample12(Last) -- DAVWikiAdmin? , 2019-09-23 08:30:05 Edit WebDAV System Administrator 2019-09-23 03:30:05

    Virtuoso Jena Provider - SPARQL Example 12


    import org.apache.jena.query.*;
    import org.apache.jena.graph.Triple;
    import org.apache.jena.graph.Node;
    import org.apache.jena.graph.Graph;
    import org.apache.jena.rdf.model.*;
    import org.apache.jena.rdf.model.RDFNode;
    import org.apache.jena.vocabulary.DC;
    import java.util.Iterator;
    
    import virtuoso.jena.driver.*;
    
    public class VirtuosoSPARQLExample12 {
    
        /**
         * Executes a SPARQL query against a virtuoso url and prints results.
         */
        public static void main(String[] args) 
        {
        String url;
        if(args.length == 0)
            url = "jdbc:virtuoso://localhost:1111";
        else
            url = args[0];
    
            Model m = VirtModel.openDatabaseModel("my:test", url, "dba", "dba");
            m.removeAll();
    
            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") ;
    
            String prolog = "PREFIX dc: <"+DC.getURI()+"> \n" ;
            
            // Query string.
            String queryString = prolog + "SELECT ?title WHERE {?x dc:title ?title}" ; 
            System.out.println("Execute query=\n"+queryString) ;
            System.out.println() ;
    
        Query query = QueryFactory.create(queryString) ;
    
    System.out.println("\n==CASE 1 ==Parse ARQ  Execute ARQ  GraphStore Virtuoso");
    //NOTE: query is parsed & executed by ARQ, so it works slow
    // and you can't use Virtuoso SPARQL features
            QueryExecution qexec = QueryExecutionFactory.create(query, m) ;
            // Or QueryExecutionFactory.create(queryString, model) ;
            System.out.println("Titles: ") ;
            try {
                ResultSet rs = qexec.execSelect() ;
                for ( ; rs.hasNext() ; ) {
                    QuerySolution rb = rs.nextSolution() ;
                    RDFNode x = rb.get("title") ;
                    if ( x.isLiteral() ) {
                        Literal titleStr = (Literal)x  ;
                        System.out.println("    "+titleStr) ;
                    } else
                        System.out.println("Strange - not a literal: "+x) ;
                }
            } finally {
                qexec.close() ;
            }
    
    
        }
    }