java - Jena:如何从 Java 中的 SPARQL (Jena) 结果集中获取整数结果？

Question

我正在使用 SPARQL 查询查询整数结果:

String qString = 
            "SELECT (COUNT(?S) AS ?C) "+
            "WHERE "+
            "{ "+
            "?S <"+p1+"> ?O ."+
            "?S <"+p2+"> ?O ."+
            "} ";
    Query q = QueryFactory.create(PREFIX+qString);
    QueryExecution qExecution = QueryExecutionFactory.sparqlService(ENDPOINT, q);
    ResultSet qResults = qExecution.execSelect();
    if(qResults.hasNext()){
        QuerySolution thisRow = qResults.next();
        int C = thisRow.get("C").toString();
    }

问题是 get() 函数使用 toString() 仅返回字符串输出。我需要一个 int 输出。我该如何去做呢？

Answer 1

我找到了解决方案。按如下方式使用文字:

String qString = 
            "SELECT (COUNT(?S) AS ?C) "+
            "WHERE "+
            "{ "+
            "?S <"+p1+"> ?O ."+
            "?S <"+p2+"> ?O ."+
            "} ";
    Query q = QueryFactory.create(PREFIX+qString);
    QueryExecution qExecution = QueryExecutionFactory.sparqlService(ENDPOINT, q);
    ResultSet qResults = qExecution.execSelect();
    if(qResults.hasNext()){
        QuerySolution thisRow = qResults.next();
        Literal C_12_literal = ((Literal) thisRow.get("C"));
        C_12 = C_12_literal.getInt();
    }

Literal 允许您获取许多数据类型，如 int、float 等。