How to convert a JavaPairRDD to Dataset?

问题:

SparkSession.createDataset() only allows List, RDD, or Seq - but it doesn't support JavaPairRDD.

So if I have a JavaPairRDD<String, User> that I want to create a Dataset from, would a viable workround for the SparkSession.createDataset() limitation to create a wrapper UserMap class that contains two fields: String and User.

Then do spark.createDataset(userMap, Encoders.bean(UserMap.class));?

回答1:

If you can convert the JavaPairRDD to List<Tuple2<K, V>> then you can use createDataset method which takes List. See below sample code.

JavaPairRDD<String, User> pairRDD = ...;
Dataset<Row> df = spark.createDataset(pairRDD.collect(), Encoders.tuple(Encoders.STRING(),Encoders.bean(User.class))).toDF("key","value");

or you can convert to RDD

Dataset<Row> df = spark.createDataset(JavaPairRDD.toRDD(pairRDD), Encoders.tuple(Encoders.STRING(),Encoders.bean(User.class))).toDF("key","value");