Added RDFStats example for Spark

Author: GezimSejdiu

sansa-examples-spark/src/main/scala/net/sansa_stack/examples/spark/rdf/RDFStats.scala

@@ -0,0 +1,51 @@
+package net.sansa_stack.examples.spark.rdf
+
+import org.apache.spark.sql.SparkSession
+import java.net.URI
+import net.sansa_stack.rdf.spark.io.NTripleReader
+import scala.collection.mutable
+import java.io.File
+import net.sansa_stack.rdf.spark.stats.RDFStatistics
+
+object RDFStats {
+  def main(args: Array[String]) = {
+    if (args.length < 2) {
+      System.err.println(
+        "Usage: RDF Statistics <input> <output>")
+      System.exit(1)
+    }
+    val input = args(0)//"src/main/resources/rdf.nt"
+    val rdf_stats_file = new File(input).getName
+    val output = args(1)
+    val optionsList = args.drop(1).map { arg =>
+      arg.dropWhile(_ == '-').split('=') match {
+        case Array(opt, v) => (opt -> v)
+        case _             => throw new IllegalArgumentException("Invalid argument: " + arg)
+      }
+    }
+    val options = mutable.Map(optionsList: _*)
+
+    options.foreach {
+      case (opt, _) => throw new IllegalArgumentException("Invalid option: " + opt)
+    }
+    println("======================================")
+    println("|        RDF Statistic example       |")
+    println("======================================")
+
+    val sparkSession = SparkSession.builder
+      .master("local[*]")
+      .config("spark.serializer", "org.apache.spark.serializer.KryoSerializer")
+      .appName("RDF Dataset Statistics example (" + rdf_stats_file + ")")
+      .getOrCreate()
+
+    val triples = NTripleReader.load(sparkSession, URI.create(input))
+
+    // compute  criterias
+    val rdf_statistics = RDFStatistics(triples, sparkSession)
+    val stats = rdf_statistics.run()
+    rdf_statistics.voidify(stats, rdf_stats_file, output)
+
+    sparkSession.stop
+
+  }
+}