Converting DataSet to Json Array Spark using Scala - json

Question

I am new to the spark and unable to figure out the solution for the following problem.
I have a JSON file to parse and then create a couple of metrics and write the data back into the JSON format.
now following is my code I am using
import org.apache.spark.sql._
import org.apache.log4j.{Level, Logger}
import org.apache.spark.sql.functions._
object quick2 {
def main(args: Array[String]): Unit = {
Logger.getLogger("org").setLevel(Level.ERROR)
val spark = SparkSession
.builder
.appName("quick1")
.master("local[*]")
.getOrCreate()
val rawData = spark.read.json("/home/umesh/Documents/Demo2/src/main/resources/sampleQuick.json")
val mat1 = rawData.select(rawData("mal_name"),rawData("cust_id")).distinct().orderBy("cust_id").toJSON.cache()
val mat2 = rawData.select(rawData("file_md5"),rawData("mal_name")).distinct().orderBy(asc("file_md5")).toJSON.cache()
val write1 = mat1.coalesce(1).toJavaRDD.saveAsTextFile("/home/umesh/Documents/Demo2/src/test/mat1/")
val write = mat2.coalesce(1).toJavaRDD.saveAsTextFile("/home/umesh/Documents/Demo2/src/test/mat2/")
}
}
Now above code is writing the proper json format.
However, matrices can contain duplicate result as well
example:
md5 mal_name
1 a
1 b
2 c
3 d
3 e
so with above code every object is getting written in single line
like this
{"file_md5":"1","mal_name":"a"}
{"file_md5":"1","mal_name":"b"}
{"file_md5":"2","mal_name":"c"}
{"file_md5":"3","mal_name":"d"}
and so on.
but I want to combine the data of common keys:
so the output should be
{"file_md5":"1","mal_name":["a","b"]}
can somebody please suggest me what shall I do here. Or if there is any other better way to approach this problem.
Thanks!

Answer 1

You can use collect_list or collect_set as per your need on mal_name column
You can directly save DataFrame/DataSet directly as JSON file
import org.apache.spark.sql.functions.{alias, collect_list}
import spark.implicits._
rawData.groupBy($"file_md5")
.agg(collect_set($"mal_name").alias("mal_name"))
.write
.format("json")
.save("json/file/location/to/save")

Answer 2

as wrote by #mrsrinivas I changed my code as per below
val mat2 = rawData.select(rawData("file_md5"),rawData("mal_name")).distinct().orderBy(asc("file_md5")).cache()
val labeledDf = mat2.toDF("file_md5","mal_name")
labeledDf.groupBy($"file_md5").agg(collect_list($"mal_name")).coalesce(1).write.format("json").save("/home/umesh/Documents/Demo2/src/test/run8/")
Keeping this quesion open for some more suggestions if any.