Spark dstream转structured streaming

上篇讲述不同topic之间join: 链接,
很多聚合操作如group by,不如SparkSql灵活.

所以想将join后topic转变成DataSet格式.
发现官网有现成demo例子

 words.foreachRDD((rdd, time) -> {
      SparkSession spark = JavaSparkSessionSingleton.getInstance(rdd.context().getConf());

      // Convert JavaRDD[String] to JavaRDD[bean class] to DataFrame
      JavaRDD<JavaRecord> rowRDD = rdd.map(word -> {
        JavaRecord record = new JavaRecord();
        record.setWord(word);
        return record;
      });
      Dataset<Row> wordsDataFrame = spark.createDataFrame(rowRDD, JavaRecord.class);

      // Creates a temporary view using the DataFrame
      wordsDataFrame.createOrReplaceTempView("words");

      // Do word count on table using SQL and print it
      Dataset<Row> w