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[英]Read array of Json-Ld Objects into a Model In Apache Jena.How to retrieve individual objects from Model?
[英]Retrieve items from a model in jena
我正在運行查詢並將結果保存到JSON文件中。 我正在將json文件作為模型加載,並嘗試檢索主題,對象和謂詞的列表。 但是我收到以下錯誤:
線程“主”中的異常org.apache.jena.riot.RiotException:[line:2,col:3]相對IRI:指向org.apache.jena.riot.system.ErrorHandlerFactory $ ErrorHandlerStd.error(ErrorHandlerFactory.java: 128)在org.apache.jena.riot.checker.CheckerIRI.iriViolations(CheckerIRI.java:138)在org.apache.jena.riot.checker.CheckerIRI.iriViolations(CheckerIRI.java:100)在org.apache.jena org.apache.jena.riot.system.ParserProfileChecker.resolveIRI(ParserProfileChecker.java:59)的org.apache.jena.riot.system.ParserProfileChecker.createURI的.riot.system.ParserProfileChecker.makeIRI(ParserProfileChecker.java:66) (ParserProfileChecker.java:112)在org.apache.jena.riot.lang.LangRDFJSON.tryParseTriples(LangRDFJSON.java:121)在org.apache.jena.riot.lang.LangRDFJSON.tryParseGraph(LangRDFJSON.java:68)在org.apache.jena.riot.lang.LangBase.parse(LangBase.java:42)上的org.apache.jena.riot.lang.LangRDFJSON.runParser(LangRDFJSON.java:56)在org.apache.jena.riot上。 RDFParserRegistry $ ReaderRIOTLang.read(RDFParserRegi stry.java:176)位於org.apache.jena.riot.RDFDataMgr.process(RDFDataMgr.java:861)位於org.apache.jena.riot.RDFDataMgr.parse(RDFDataMgr.java:667)位於org.apache.jena org.apache.jena.riot.RDFDataMgr.read(RDFDataMgr.java:145)上的.riot.RDFDataMgr.read(RDFDataMgr.java:212)在org.apache.jena.riot.RDFDataMgr.read(RDFDataMgr.java:134) )於org.apache.jena.util的org.apache.jena.util.FileManager.loadModelWorker(FileManager.java:305)的org.apache.jena.riot.adapters.AdapterFileManager.readModelWorker(AdapterFileManager.java:282)處。 Main.main(Main.java:51)上的FileManager.loadModel(FileManager.java:292)
我的代碼是:
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;
import org.apache.jena.query.Query;
import org.apache.jena.query.QueryExecution;
import org.apache.jena.query.QueryExecutionFactory;
import org.apache.jena.query.QueryFactory;
import org.apache.jena.query.QuerySolution;
import org.apache.jena.query.ResultSet;
import org.apache.jena.query.ResultSetFormatter;
import org.apache.jena.rdf.model.Literal;
import org.apache.jena.rdf.model.Model;
import org.apache.jena.rdf.model.RDFNode;
import org.apache.jena.rdf.model.Resource;
import org.apache.jena.rdf.model.Statement;
import org.apache.jena.rdf.model.StmtIterator;
import org.apache.jena.util.FileManager;
public class Main {
public static void main(String[] args) {
// TODO Auto-generated method stub
String queryString = "PREFIX owl: <http://www.w3.org/2002/07/owl#>"
+ "PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>"
+ "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>"
+ "PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>"
+ "PREFIX foaf: <http://xmlns.com/foaf/0.1/>" + "PREFIX dc: <http://purl.org/dc/elements/1.1/>"
+ "PREFIX dbr: <http://dbpedia.org/resource/>" + "PREFIX dbpedia2: <http://dbpedia.org/property/>"
+ "PREFIX dbpedia: <http://dbpedia.org/>" + "PREFIX skos: <http://www.w3.org/2004/02/skos/core#>"
+ "PREFIX dbo: <http://dbpedia.org/ontology/>" + "select distinct ?p ?o where {"
+ "dbr:Cristiano_Ronaldo ?p ?o " + "filter(langMatches(lang(?o),'en'))" +
"}";
Query query = QueryFactory.create(queryString);
QueryExecution qexec = QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql", query);
ResultSet results = qexec.execSelect();
FileOutputStream oFile;
try {
oFile = new FileOutputStream("output4.json", false);
ResultSetFormatter.outputAsJSON(oFile, results);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
qexec.close();
FileManager.get().addLocatorClassLoader(Main.class.getClassLoader());
Model model = FileManager.get().loadModel("output4.json", null, "RDF/JSON");
StmtIterator iter = model.listStatements();
try {
while (iter.hasNext()) {
Statement stmt = iter.next();
Resource s = stmt.getSubject();
Resource p = stmt.getPredicate();
RDFNode o = stmt.getObject();
System.out.println(s.toString());
System.out.println(p.toString());
System.out.println(o.toString());
}
} finally {
if (iter != null)
iter.close();
}
}
}
根據AKSW的建議,我已經嘗試使用構造查詢:
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import org.apache.jena.query.Query;
import org.apache.jena.query.QueryExecution;
import org.apache.jena.query.QueryExecutionFactory;
import org.apache.jena.query.QueryFactory;
import org.apache.jena.query.ResultSetFactory;
import org.apache.jena.query.ResultSetFormatter;
import org.apache.jena.query.ResultSetRewindable;
import org.apache.jena.rdf.model.Model;
import org.apache.jena.rdf.model.RDFNode;
import org.apache.jena.rdf.model.Resource;
import org.apache.jena.rdf.model.Statement;
import org.apache.jena.rdf.model.StmtIterator;
import org.apache.jena.util.FileManager;
public class Main {
public static void main(String[] args) {
// TODO Auto-generated method stub
String queryString = "PREFIX owl: <http://www.w3.org/2002/07/owl#>"
+ "PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>"
+ "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>"
+ "PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>"
+ "PREFIX foaf: <http://xmlns.com/foaf/0.1/>" + "PREFIX dc: <http://purl.org/dc/elements/1.1/>"
+ "PREFIX dbr: <http://dbpedia.org/resource/>" + "PREFIX dbpedia2: <http://dbpedia.org/property/>"
+ "PREFIX dbpedia: <http://dbpedia.org/>" + "PREFIX skos: <http://www.w3.org/2004/02/skos/core#>"
+ "PREFIX dbo: <http://dbpedia.org/ontology/>" + "select distinct ?p ?o where {"
+ "dbr:Cristiano_Ronaldo ?p ?o " + "filter(langMatches(lang(?o),'en'))" +
"}";
Query query = QueryFactory.create(queryString);
QueryExecution qexec = QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql", query);
FileOutputStream oFile;
try {
oFile = new FileOutputStream("output4.ttl", false);
Model result21 = qexec.execConstruct();
result21.write(oFile, "TURTLE");
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
qexec.close();
FileManager.get().addLocatorClassLoader(Main.class.getClassLoader());
Model model = FileManager.get().loadModel("output4.ttl", null, "TURTLE");
StmtIterator iter = model.listStatements();
try {
while (iter.hasNext()) {
Statement stmt = iter.next();
Resource s = stmt.getSubject();
Resource p = stmt.getPredicate();
RDFNode o = stmt.getObject();
System.out.println(s.toString());
System.out.println(p.toString());
System.out.println(o.toString());
}
} finally {
if (iter != null)
iter.close();
}
}
}
打印的結果很奇怪,不能正確提供主題,賓語和謂詞。 以下是控制台中打印的響應: 結果
問題是您正在運行SELECT查詢,該查詢將為您提供結果集。 該結果集並不代表您可能期望的RDF三元組。 特別是由於僅選擇p
和o
,因此將丟失主題。 然后將該結果集另存為JSON,有關格式的說明,請參見https://www.w3.org/TR/rdf-sparql-json-res/ 。 因此,JSON文件中沒有三元組,您可以將其加載回JENA模型。
解決方案是改用SPARQL CONSTRUCT 。 查詢可以如下:
PREFIX dbr: <http://dbpedia.org/resource/>
CONSTRUCT {
dbr:Cristiano_Ronaldo ?p ?o .
} WHERE {
dbr:Cristiano_Ronaldo ?p ?o .
FILTER(LANGMATCHES(LANG(?o),'en'))
}
另外,您必須調整Jena API中的方法調用:
Model model = qexec.execConstruct(); // instead of execSelect();
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