while((reader=br.readLine())!=null)
{
System.out.println(reader);
type="";
String queryNew="select ?y ?z where {"+reader+" <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?z . }";
Query query=QueryFactory.create(queryNew);
ARQ.getContext().setTrue(ARQ.useSAX);
QueryExecution qexec = QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql", query);
ResultSet results = qexec.execSelect();
while(results.hasNext())
{
QuerySolution soln=results.nextSolution();
type=type+" "+soln.get("?z");
System.out.println(soln.get("?y")+" "+soln.get("?z"));
}
bw.write(reader+" "+type+"\n");
}
从文件中我正在阅读演员姓名，然后尝试获取每个演员的所有rdf:type链接。当结果打印出第一个actor时，执行的其余部分会被卡住。 '读者'只不过是一个演员的名字，它是dbpedia资源。有人可以告诉我代码中可能出错的地方吗？
答案 0 :(得分：4)
您没有显示您的数据，但假设该文件只包含了actor的名称，正如您所说，那么您实际询问的查询是这样的：
select ?y ?z where {
"Matt Damon" rdf:type ?z
}
这永远不会返回任何结果，因为RDF三元组的主题始终是RDF资源，而不是字符串文字。
您应该将查询更改为：
prefix dbpprop: <http://dbpedia.org/property/>
prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
select ?actor ?type where {
?actor dbpprop:name "Matt Damon"@en ;
rdf:type ?type
}
换句话说“什么是rdf：名称（英文）是Matt Damon的资源的类型？”
答案 1 :(得分：1)
正如Ian Dickinson在his answer中指出的那样，你没有向我们展示数据，也没有向我们展示reader的确切价值，所以很难确切地说出出了什么问题。听起来你需要根据
?actor rdfs:label ?label
其中?label是您感兴趣的actor的名称。如果您像在
String queryNew = "select ?y ?z where {" + reader + " <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?z . }";
你正在接受SPARQL注入攻击。例如，如果reader包含更多SPARQL查询文本会发生什么？ （另外，由于rdf:type是如此常用，因此SPARQL实际上允许您将其缩写为a，如?actor a dbpedia-owl:Person中所示。）为了避免此类问题，Jena提供{{3}这将负责正确的逃避。另请注意，RDF区分普通文字，例如"Richard Dreyfuss"和语言标记字符串，例如"Richard Dreyfuss"@en。这意味着您可能希望在查询中包含语言标记。最后，请注意DBpedia中可能存在多个具有给定标签的内容。 Heres的代码使用参数化的SPARQL字符串，查找标签为"Richard Dreyfuss"@en的资源及其所有RDF类型：
import com.hp.hpl.jena.query.ParameterizedSparqlString;
import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.query.QueryExecutionFactory;
import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.query.ResultSetFormatter;
import com.hp.hpl.jena.rdf.model.Literal;
import com.hp.hpl.jena.rdf.model.ResourceFactory;
public class DBpediaQueryExample {
public static void main(String[] args) {
/*
* A typed literal: the name Richard Dreyfuss in English. In SPARQL
* this is written as "Richard Dreyfuss"@en.
*/
final Literal richardDreyfuss = ResourceFactory.createLangLiteral( "Richard Dreyfuss", "en" );
/*
* A parameterized SPARQL string for the query. Using this, along with
* the various setZZZ(...) methods can prevent some SPARQL injection
* attacks by doing proper escaping.
*/
final ParameterizedSparqlString queryString = new ParameterizedSparqlString(
"prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>\n" +
"\n" +
"select ?resource ?type where {\n" +
" ?resource a ?type ;\n" +
" rdfs:label ?label .\n" +
"}" );
/*
* Fill in "Richard Dreyfuss"@en for the ?label.
*/
queryString.setLiteral("label", richardDreyfuss );
/*
* Get a query execution that will run against the DBpedia SPARQL
* endpoint, and will use the parameterized query.
*/
final QueryExecution exec = QueryExecutionFactory.sparqlService(
"http://dbpedia.org/sparql",
queryString.asQuery() );
/*
* Execute the query to produce a result set, and format it nicely.
*/
final ResultSet results = exec.execSelect();
ResultSetFormatter.out( results );
}
}
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| resource | type |
=================================================================================================================================================
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://www.w3.org/2002/07/owl#Thing> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/ActorsFromLosAngeles,California> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/AmericanFilmActors> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/AmericanTelevisionActors> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/ontology/Agent> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/ontology/Person> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://umbel.org/umbel/rc/Actor> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://schema.org/Person> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://xmlns.com/foaf/0.1/Person> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/AmericanComedians> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/Comedian109940146> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/JewishActors> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/PeopleFromBrooklyn> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/Adult109605289> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/Communicator109610660> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/LivingPeople> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/Object100002684> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/PeopleWithBipolarDisorder> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/Person100007846> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/Whole100003553> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/YagoLegalActor> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/Entertainer109616922> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/AlternateHistoryWriters> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/Actor109765278> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/AmericanConscientiousObjectors> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/AmericanHistoricalNovelists> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/ConscientiousObjector109957013> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/Dissenter110018021> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/Novelist110363573> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/Performer110415638> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/Writer110794014> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/CausalAgent100007347> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/LivingThing100004258> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/Organism100004475> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/JewishComedians> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/JewishPacifists> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/Pacifist110390199> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/PhysicalEntity100001930> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/YagoLegalActorGeo> |
| <http://dbpedia.org/resource/Richard_Dreyfuss> | <http://dbpedia.org/class/yago/PeopleFromQueens> |
| <http://sw.opencyc.org/2008/06/10/concept/en/RichardDreyfuss> | <http://sw.opencyc.org/2008/06/10/concept/en/ActorInMovies> |
| <http://sw.opencyc.org/2008/06/10/concept/en/RichardDreyfuss> | <http://sw.opencyc.org/2008/06/10/concept/en/MaleHuman> |
| <http://sw.opencyc.org/2008/06/10/concept/Mx4rwOREVpwpEbGdrcN5Y29ycA> | <http://sw.opencyc.org/2008/06/10/concept/Mx4rvVjWoZwpEbGdrcN5Y29ycA> |
| <http://sw.opencyc.org/2008/06/10/concept/Mx4rwOREVpwpEbGdrcN5Y29ycA> | <http://sw.opencyc.org/2008/06/10/concept/Mx4rwMRyTJwpEbGdrcN5Y29ycA> |
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