The Serve method processes predicted results. Also, you can combine multiple predicted results into one for more than one predictive model.

The Java class for serve is written as follows:

    package org.template.recommendation;

    import org.apache.predictionio.controller.java.LJavaServing;
    import scala.collection.Seq;

    public class Serving extends LJavaServing<Query, PredictedResult> {

      @Override
      public PredictedResult serve(Query query, Seq<PredictedResult>
          predictions) {
        return predictions.head();
      }
    }

The Scala version would obviously be smaller and the code is shown here:

    package MyRecommedationScala

    import org.apache.predictionio.controller.LServing

    class Serving
    extends LServing[Query, PredictedResult] {

      override
      def serve(query: Query,
      predictedResults: Seq[PredictedResult]): PredictedResult = {
        predictedResults.head
      }
    }

Note that we call the head method and the Seq function (Trait in Scala) to order the results.

Note that we are skipping the evaluation part of the engine. We will cover it in the next chapter in detail.