在 JENA virtuoso 的 SPARQL 查询中使用 BIND 时出现空指针异常错误

Question

我在运行宁 SPARQL 查询时出现以下错误，

ERROR [main] (RDFDefaultErrorHandler.java:40) - (line 7 column 7): {E201} The attributes on this property element, are not permitted with any content; expecting end element tag.
ERROR [main] (RDFDefaultErrorHandler.java:40) - (line 7 column 38): {E201} XML element <res:binding> inside an empty property element, whose attributes prohibit any content.
ERROR [main] (RDFDefaultErrorHandler.java:40) - (line 7 column 52): {E201} XML element <res:variable> inside an empty property element, whose attributes prohibit any content.
ERROR [main] (RDFDefaultErrorHandler.java:40) - (line 7 column 57): {E201} The attributes on this property element, are not permitted with any content; expecting end element tag.
 WARN [main] (RDFDefaultErrorHandler.java:36) - (line 8 column 135): {W102} unqualified use of rdf:datatype is deprecated.
java.lang.NullPointerException
    at com.hp.hpl.jena.rdf.arp.impl.XMLHandler.endElement(XMLHandler.java:149)
    at org.apache.xerces.parsers.AbstractSAXParser.endElement(Unknown Source)
    at org.apache.xerces.impl.XMLNamespaceBinder.handleEndElement(Unknown Source)
    at org.apache.xerces.impl.XMLNamespaceBinder.endElement(Unknown Source)
    at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanEndElement(Unknown Source)
    at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(Unknown Source)
    at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
    at org.apache.xerces.parsers.DTDConfiguration.parse(Unknown Source)
    at org.apache.xerces.parsers.DTDConfiguration.parse(Unknown Source)
    at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
    at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
    at com.hp.hpl.jena.rdf.arp.impl.RDFXMLParser.parse(RDFXMLParser.java:142)
    at com.hp.hpl.jena.rdf.arp.JenaReader.read(JenaReader.java:158)
    at com.hp.hpl.jena.rdf.arp.JenaReader.read(JenaReader.java:145)
    at com.hp.hpl.jena.rdf.arp.JenaReader.read(JenaReader.java:215)
    at com.hp.hpl.jena.rdf.model.impl.ModelCom.read(ModelCom.java:197)
    at com.hp.hpl.jena.sparql.engine.http.QueryEngineHTTP.execModel(QueryEngineHTTP.java:169)
    at com.hp.hpl.jena.sparql.engine.http.QueryEngineHTTP.execDescribe(QueryEngineHTTP.java:162)
    at com.hp.hpl.jena.sparql.engine.http.QueryEngineHTTP.execDescribe(QueryEngineHTTP.java:160)
    at com.hospital.SPARQLQuery.main(SPARQLQuery.java:34)

示例 TTL 文件数据

@prefix dc:   <http://purl.org/dc/elements/1.1/> .
@prefix :     <http://example.org/book/> .
@prefix ns:   <http://example.org/ns#> .

:book1  dc:title     "SPARQL Tutorial" .
:book1  ns:price     42 .
:book1  ns:discount  0.2 .

:book2  dc:title     "The Semantic Web" .
:book2  ns:price     23 .
:book2  ns:discount  0.25 .

我正在使用 Virtuoso SPARQL 端点运行查询

这是我的代码，我是运行ning。

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.query.QueryExecutionFactory;
import com.hp.hpl.jena.rdf.model.Model;


public class SPARQLQuery {

    private static final Logger logger = LogManager.getLogger(SPARQLQuery.class);

    public static void main(String[] args) {

        try {
            String queryString = "PREFIX  dc:  <http://purl.org/dc/elements/1.1/>\r\n" + 
                    "PREFIX  ns:  <http://example.org/ns#>\r\n" + 
                    "\r\n" + 
                    "SELECT  ?title ?price\r\n" + 
                    "{  ?x ns:price ?p .\r\n" + 
                    "   ?x ns:discount ?discount\r\n" + 
                    "   BIND (?p*(1-?discount) AS ?price)\r\n" + 
                    "   FILTER(?price < 20)\r\n" + 
                    "   ?x dc:title ?title . \r\n" + 
                    "}";

            QueryExecution qexec = QueryExecutionFactory.sparqlService("http://localhost:8890/sparql", queryString);
            Model results = qexec.execDescribe();

            results.write(System.out,"TTL");

        }catch(Exception ex) {
            ex.printStackTrace();
        }
    }
}

Maven 依赖

<dependency>
    <groupId>com.hp.hpl.jena</groupId>
    <artifactId>arq</artifactId>
    <version>2.8.8</version>
</dependency>

我在 SPARQL 查询中使用 BIND 时遇到奇怪的问题。我不明白实际问题是什么，或者我不明白为什么会这样。此外，我将 Virtuoso 用于图形数据存储，并将 Jena 库用于运行ning SPARQL 查询。虽然运行查询我正在 error.I 没有在 google.

上找到任何解决方案

Answer 1

正如@AKSW 在评论中所揭示的那样，答案是

更新为 current Jena (and possibly current Virtuoso server [whether Enterprise or Open Source], Virtuoso Provider for Jena, and/or Virtuoso JDBC driver)
使用正确的 call/query 配对（即，使用 SPARQL SELECT 查询调用 Jena .execSelect()，或使用 SPARQL DESCRIBE 查询调用 Jena .execDescribe() ).

在 JENA virtuoso 的 SPARQL 查询中使用 BIND 时出现空指针异常错误

Null pointer exception error while using BIND in SPARQL query in JENA virtuoso

sparql

jena

virtuoso

openlink-virtuoso