Java stubs for ALSModel.

mllib/src/main/scala/org/apache/spark/mllib/api/PythonMLLibAPI.scala

@@ -19,6 +19,7 @@ import org.apache.spark.api.java.JavaRDD
 import org.apache.spark.mllib.regression._
 import org.apache.spark.mllib.classification._
 import org.apache.spark.mllib.clustering._
+import org.apache.spark.mllib.recommendation._
 import org.apache.spark.rdd.RDD
 import java.nio.ByteBuffer
 import java.nio.ByteOrder
@@ -194,4 +195,37 @@ class PythonMLLibAPI extends Serializable {
     ret.add(serializeDoubleMatrix(model.clusterCenters))
     return ret
   }
+
+  private def unpackRating(ratingBytes: Array[Byte]): Rating = {
+    val bb = ByteBuffer.wrap(ratingBytes)
+    bb.order(ByteOrder.nativeOrder())
+    val user = bb.getInt()
+    val product = bb.getInt()
+    val rating = bb.getDouble()
+    return new Rating(user, product, rating)
+  }
+
+  /**
+   * Java stub for Python mllib ALSModel.train().  This stub returns a handle
+   * to the Java object instead of the content of the Java object.  Extra care
+   * needs to be taken in the Python code to ensure it gets freed on exit; see
+   * the Py4J documentation.
+   */
+  def trainALSModel(ratingsBytesJRDD: JavaRDD[Array[Byte]], rank: Int,
+      iterations: Int, lambda: Double, blocks: Int): MatrixFactorizationModel = {
+    val ratings = ratingsBytesJRDD.rdd.map(unpackRating)
+    return ALS.train(ratings, rank, iterations, lambda, blocks)
+  }
+
+  /**
+   * Java stub for Python mllib ALSModel.trainImplicit().  This stub returns a
+   * handle to the Java object instead of the content of the Java object.
+   * Extra care needs to be taken in the Python code to ensure it gets freed on
+   * exit; see the Py4J documentation.
+   */
+  def trainImplicitALSModel(ratingsBytesJRDD: JavaRDD[Array[Byte]], rank: Int,
+      iterations: Int, lambda: Double, blocks: Int, alpha: Double): MatrixFactorizationModel = {
+    val ratings = ratingsBytesJRDD.rdd.map(unpackRating)
+    return ALS.trainImplicit(ratings, rank, iterations, lambda, blocks, alpha)
+  }
 }