分类： 技术宅

该例读取下面三个IRI的内容，并返回RDF数据。这个例子比较有意思的是能够在
数据库里面创建一个Graph。
IRI:
http://kidehen.idehen.net/dataspace/person/kidehen#this
http://www.w3.org/People/Berners-Lee/card#i
http://demo.openlinksw.com/dataspace/person/demo#this

import org.apache.jena.query.Query;
import org.apache.jena.query.QueryFactory;
import org.apache.jena.query.QuerySolution;
import org.apache.jena.query.ResultSet;
import org.apache.jena.rdf.model.RDFNode;

import virtuoso.jena.driver.*;

public class VirtuosoSPARQLExample2 {

	/**
	 * 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];

/*			STEP 1			*/
		/*
		 * 这里添加"Example2"后，类似于打开一个Graph叫做"Example2",，
		 * 如果没有会自动生成一个名为"Example2"的图
		 */
		VirtGraph graph = new VirtGraph ("Example2", url, "dba", "dba");

/*			STEP 2			*/
/*		Load data to Virtuoso		*/
		//清除"Example2" Graph
		graph.clear ();
		
		/*
		 * 这里是读取IRI的Graph并存储到服务器的"Example2"
		 * 这里的读取，类似于在Web端在Quad Store Upload上的操作类似
		 * 如果网络连接不了，可以尝试删除下面的那些失败的内容
		 */
		System.out.print ("Begin read from 'http://www.w3.org/People/Berners-Lee/card#i'  ");
		graph.read("http://www.w3.org/People/Berners-Lee/card#i", "RDF/XML");
		System.out.println ("\t\t\t Done.");

		System.out.print ("Begin read from 'http://demo.openlinksw.com/dataspace/person/demo#this'  ");
		graph.read("http://demo.openlinksw.com/dataspace/person/demo#this", "RDF/XML");
		System.out.println ("\t Done.");

		System.out.print ("Begin read from 'http://kidehen.idehen.net/dataspace/person/kidehen#this'  ");
		graph.read("http://kidehen.idehen.net/dataspace/person/kidehen#this", "RDF/XML");
		System.out.println ("\t Done.");


/*			STEP 3			*/
/*		Select only from VirtGraph	*/
		Query sparql = QueryFactory.create("SELECT ?s ?p ?o WHERE { ?s ?p ?o }");

/*			STEP 4			*/
		VirtuosoQueryExecution vqe = VirtuosoQueryExecutionFactory.create (sparql, graph);

		ResultSet results = vqe.execSelect();
		while (results.hasNext()) {
			QuerySolution result = results.nextSolution();
		    RDFNode graph_name = result.get("graph");
		    RDFNode s = result.get("s");
		    RDFNode p = result.get("p");
		    RDFNode o = result.get("o");
		    System.out.println(graph_name + " { " + s + " " + p + " " + o + " . }");
		}

		System.out.println("graph.getCount() = " + graph.getCount());
	}
}