Scala Sparql query with Apache Jena

Question

I am trying to build a sparql query in scala. I have issues using the apache arq library which is meant for java. The dependencies seem to be all fine but Intellij cannot resolve the ParameterizedSparqlString constructor and resulting the QueryEngineHTTP constructor. Im running jdk 1.8. Any ideas? Appreciated!!

val sparqlentities = namedEntitiesByDocument
  .mapPartitions(iter => {
    val sparqlEndpoint = "localhost:1643";
    iter.map( t => {
      t._1, t._2.map(namedEntity => {
        val sparqlQuery = "" + "SELECT  ?s { \n ?s rdfs:label" + namedEntity.surfaceForm + " . \n }"
        val query = QueryFactory.create(sparqlQuery, Syntax.syntaxARQ)
        // val querySolutionMap = new QuerySolutionMap()
        val parameterizedSparqlString = new ParameterizedSparqlString(query.toString(), new QuerySolutionMap())
        val httpQuery = new QueryEngineHTTP(sparqlEndpoint,parameterizedSparqlString.asQuery())
        val results = httpQuery.execSelect()
        while (results.hasNext()) {
          val solution = results.next()
          val fin_result = solution.get("s").asLiteral().getLexicalForm()
          (namedEntity.surfaceForm, fin_result)
        }
      })
    })
  })

Which Jena version? Do you use Maven? If so, show the Maven dependency, please. And finally, do you really get a compiler error? — UninformedUser, Nov 26 '16 at 18:47

score 3 · Answer 1 · answered Nov 26 '16 at 18:54

(comments do not work for complex text, hence this answer)

You do not need a ParameterizedSparqlString if you are doing string building yourself. Creating a query string, parsing it, then calling .toString is a bit convoluted. You can use QueryFactory then QueryExecutionFactory.

Note that at

val sparqlQuery = "" + "SELECT ?s { \n ?s rdfs:label" + namedEntity.surfaceForm + " . \n }" The namedEntity.surfaceForm must be in SPARQL syntax, e.g a string needs "" around it, otherwise you will get a parse error in SPARQL.

score 1 · Answer 2 · answered Feb 07 '17 at 19:50

@Becher, per @AKSW's question, we need to know how you're trying to resolve dependencies. IntelliJ gives you a few options -- I use SBT, which I think is pretty common, with Ivy (through the IvyIDEA plug-in.) But, you can use Maven directly or just add jars to a library.

This is a pretty helpful page in any case https://mvnrepository.com/artifact/org.apache.jena/jena-arq/3.1.1

Scala Sparql query with Apache Jena

2 Answers2