Tag: SPARQL查询Virtuoso

想要使用JAVA连接Virtuoso，我想最关心的额就是如何连接并查询，下面代码演示了如何操作

import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.RDFNode;

import virtuoso.jena.driver.*;

public class VirtuosoSPARQLExample1 {

	/*
	 * Executes a SPARQL query against a virtuoso url and prints results.
	 */
	public static void main(String[] args) {

		String url;
		if(args.length == 0)
		//如果Virtuoso安装在本体，这个是默认的地址和端口
		    url = "jdbc:virtuoso://localhost:1111"; 
		else
		    url = args[0];

/*			STEP 1			*/
		//连接服务器，两个“dba”分别是账号和密码，是初始状态Virtuoso的默认值
		VirtGraph set = new VirtGraph (url, "dba", "dba");

/*			STEP 2			*/


/*			STEP 3			*/
/*		Select all data in virtuoso	*/
		//给出查询语句，这里使用的是Jena框架里的
		Query sparql = QueryFactory.create("SELECT * WHERE { GRAPH ?graph { ?s ?p ?o } } limit 100");

/*			STEP 4			*/
		//在服务器"set"上执行查询语句"sparql"
		VirtuosoQueryExecution vqe = VirtuosoQueryExecutionFactory.create (sparql, set);

		//获取结果，这些就和Jena的操作一模一样了
		ResultSet results = vqe.execSelect();
		while (results.hasNext()) {
			QuerySolution result = results.nextSolution();
		    RDFNode graph = result.get("graph");
		    RDFNode s = result.get("s");
		    RDFNode p = result.get("p");
		    RDFNode o = result.get("o");
		    System.out.println(graph + " { " + s + " " + p + " " + o + " . }");
		}
	}
}