Spark Streaming：从 Kafka 读取 JSON 并添加 event_time

Question

I am trying to write a Stateful Spark Structured Streaming job that reads from Kafka. As part of the requirement I need to add 'event_time' to my stream as an additional column. I am trying something like this:

val schema = spark.read.json("sample-data/test.json").schema
val myStream = sparkSession
      .readStream
      .format("kafka")
      .option("kafka.bootstrap.servers", "localhost:9092")
      .option("subscribe", "myTopic")
      .load()
val df = myStream.select(from_json($"value".cast("string"), schema).alias("value"))
val withEventTime = df.selectExpr("*", "cast (value.arrivalTime as timestamp) as event_time")

But I keep getting message:

cannot resolve 'arrivalTime' given input columns: [value]

How do I refer to all the elements in my JSON?

Answer 1

I believe I was able to solve this using this:

val withEventTime = df.withColumn("event_time",to_timestamp(col("value. arrivalTime")))

Not sure why this worked & not the other one.