Spark2 Kafka Structured Streaming Java doesn't know from_json function

Question

I've got a question with regards to Spark structured streaming on a Kafka stream.

I have a schema of type:

StructType schema = new StructType()
                .add("field1", StringType)
                .add("field2", StringType)
                .add("field3", StringType)
                .add("field4", StringType)
                .add("field5", StringType);

I bootstrap my stream from Kafka topic like:

Dataset<Row> ds1 = spark
                .readStream()
                .format("kafka")
                .option("kafka.bootstrap.servers", "brokerlist")
                .option("zookeeper.connect", "zk_url")
                .option("subscribe", "topic")
                .option("startingOffsets", "earliest")
                .option("max.poll.records", 10)
                .option("failOnDataLoss", false)
                .load();

next convert to string,string type:

Dataset<Row> df1 = ds1.selectExpr("CAST(key AS STRING)", "CAST(value AS STRING)");

Now I would like to convert the value field (which is a JSON) to the previously converted schema which should make SQL queries easier:

Dataset<Row> df2 = df1.select(from_json("value", schema=schema).as("data").select("single_column_field");

It seems that Spark 2.3.1 doesn't know the from_json function?

This is my imports:

import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Row;
import org.apache.spark.sql.SparkSession;
import org.apache.spark.sql.streaming.OutputMode;
import org.apache.spark.sql.streaming.StreamingQueryException;
import org.apache.spark.sql.types.StructType;

Any idea on how to solve this? Please note that I'm not looking for a Scala solution, but a pure Java based solution!

Answer 1

This code working for me. Hope it'll helpful

val df = spark
  .readStream
  .format("kafka")
  .option("kafka.bootstrap.servers", "192.168.34.216:9092")
  .option("subscribe", "topicName")
  .load()
//df.show();
import spark.implicits._
val comingXDR = df.select("value").as[String].withColumn("_tmp", split($"value", "\\,")).withColumn("MyNewColumnName1", $"_tmp".getItem(0)).withColumn("MyNewColumnName2", $"_tmp".getItem(1)).withColumn("MyNewColumnName3", $"_tmp".getItem(2)).withColumn("MyNewColumnName4", $"_tmp".getItem(3)).drop("value").drop("_tmp")