SPARQL 照会の発行

次のプログラムは、SPARQL 照会言語を使用して RDF ストア内のデータを照会する方法を示しています。

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

import com.hp.hpl.jena.query.Dataset;
import com.hp.hpl.jena.query.Query;
import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.query.QuerySolution;
import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.rdf.model.Model;
import com.ibm.rdf.store.Store;
import com.ibm.rdf.store.StoreManager;
import com.ibm.rdf.store.exception.RdfStoreException;
import com.ibm.rdf.store.jena.RdfStoreFactory;
import com.ibm.rdf.store.jena.RdfStoreQueryExecutionFactory;
import com.ibm.rdf.store.jena.RdfStoreQueryFactory;

public class RDFStoreSampleQuery   {
	
		
	public static void main(String[] args) throws SQLException, IOException {
		
		Connection conn = null;
		Store store = null;
		String storeName = "sample";
		String schema = "db2admin";

		// Get a connection to the Db2 database.
		try {
			Class.forName("com.ibm.db2.jcc.DB2Driver");
			conn = DriverManager.getConnection(
					"jdbc:db2://localhost:50000/dbrdf", "db2admin",
					"db2admin");
		} catch (ClassNotFoundException e1) {
			e1.printStackTrace();
		}

		
		try {
			
			/* Connect to required RDF store in the specified schema. */
			store = StoreManager.connectStore(conn, schema, storeName);
			
			/* This is going to be our SPARQL query i.e. select triples 
			 in the default graph where object is <ibm.com>
			 */
       String query = "SELECT * WHERE { ?s ?p 
      <https://www.ibm.com> }";
			
			/* Create the Query object for the SPARQL string. */
			Query q = RdfStoreQueryFactory.create(query);
			
			/* Get the Dataset interface of the RDF store. */
			Dataset ds = RdfStoreFactory.connectDataset(store, conn);
			
			/* Create a QueryExecution object, by providing the query to execute
			 and the dataset against which it to be executed. */
			QueryExecution qe = RdfStoreQueryExecutionFactory.create(q, ds);
					
			long rows = 0;
			Model m = null;
			
			/* Based on the SPARQL query type, call the proper execution
			  method. */
			if (q.isSelectType()) {
				ResultSet rs = qe.execSelect();
				while (rs.hasNext()) {
					QuerySolution qs = rs.next();
					System.out.println(qs);
					System.out.println();
					rows++;
				}
			}
			else if ( q.isDescribeType() ) {
					m = qe.execDescribe();
					m.write(System.out, "N-TRIPLE");
			}
			else if ( q.isAskType() ) {
				System.out.println(qe.execAsk());
								
			}
			else if (q.isConstructType()) {
				m = qe.execConstruct();
				m.write(System.out, "N-TRIPLE");
			}
				
			
			/* Close the QueryExecution object. This is required to ensure
			 no JDBC statement leaks. */
			qe.close();
			
			// Display the # of rows returned
			if ( m != null ) {
				System.out.println("Number of Rows  : " + m.size());
				m.close();
			}
			else {
				System.out.println("Number of Rows  : " + rows);
			}
			
		}
		catch(RdfStoreException e) {
			
			e.printStackTrace();
		}
		catch(Exception e) {
			e.printStackTrace();
		}
		
	}
	
}