如何在create期间在apache.jena.queryExecutionFactory上调试NullPointerException？

Question

我正在与org.apache.jena与karaf合作。在尝试查询我的模型时，我得到了一个NullPointerException，我打印了用于创建查询的所有变量，所有（queryString，inferedModel）都不是null。这是我的代码的样子：

Model model = JenaEngine.readModel(inputDataOntology);
if (model == null) {
    return "model null !";
}
Model inferedModel = JenaEngine.readInferencedModelFromRuleFile(model, inputRule);
if (inferedModel == null) {
    return "inferedModel null !";
}
JenaEngine.updateValueOfDataTypeProperty(inferedModel, ns, "Peter", "age", 10);
JenaEngine.updateValueOfObjectProperty(inferedModel, ns, "Peter", "estFilsDe", "Femme1");
JenaEngine.createInstanceOfClass(model, ns, "Femme", "abc");
//query on the model
String prefixQuery = "PREFIX ns: <http://www.owl-ontologies.com/Ontology1291196007.owl#>\n" +
    "PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>\n" +
    "PREFIX owl: <http://www.w3.org/2002/07/owl#>\n"+
    "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>\n";
String selectQuery = "SELECT ?user ?age WHERE {\n ?user ns:age ?age.\n }";
QueryExecution queryExecution = QueryExecutionFactory.create(prefixQuery+selectQuery, inferedModel);
ResultSet rs = queryExecution.execSelect();
List<String> users = new ArrayList();
while(rs.hasNext()) {
    QuerySolution qs = rs.next();
    Resource user = qs.getResource("user");
    users.add(user.getLocalName());
}
String results = "";
for(String user : users) {
    results+=user+" ";
}
return results;

我在初始化NullPointerException变量的行上得到一个QueryExecution。

这是错误的堆栈跟踪：

java.lang.NullPointerException
        at org.apache.jena.query.ARQ.isTrue(ARQ.java:650)
        at org.apache.jena.sparql.lang.ParserBase.<init>(ParserBase.java:292)
        at org.apache.jena.sparql.lang.SPARQLParserBase.<init>(SPARQLParserBase.java:43)
        at org.apache.jena.sparql.lang.sparql_11.SPARQLParser11Base.<init>(SPARQLParser11Base.java:22)
        at org.apache.jena.sparql.lang.sparql_11.SPARQLParser11.<init>(SPARQLParser11.java:4974)
        at org.apache.jena.sparql.lang.ParserSPARQL11.perform(ParserSPARQL11.java:91)
        at org.apache.jena.sparql.lang.ParserSPARQL11.parse$(ParserSPARQL11.java:52)
        at org.apache.jena.sparql.lang.SPARQLParser.parse(SPARQLParser.java:34)
        at org.apache.jena.query.QueryFactory.parse(QueryFactory.java:147)
        at org.apache.jena.query.QueryFactory.create(QueryFactory.java:79)
        at org.apache.jena.query.QueryFactory.create(QueryFactory.java:52)
        at org.apache.jena.query.QueryFactory.create(QueryFactory.java:40)
        at fr.conceptit.tuto.web.Main.work(Main.java:71)
        ...

我正在通过Karaf部署我的应用程序可能问题来自那里。这是我在Karaf上的捆绑列表的屏幕截图。请注意，我添加了所有Jena Jars.Karaf Bundles list

Answer 1

感谢@AndyS的评论，我能够找到一种方法让它发挥作用。他指出正确的方向说：

关于ARQ.isTrue的NPE：ARQ未正确初始化

确实这就是问题，我通过初始化ARQ而不是JenaSystem解决了这个问题。基本上我在org.apache.jena.query.ARQ.init()有任何调用之前添加了Jena并且它有效。再次感谢您的帮助和支持。