将2个Scala Spark Dataframe和一个Long值转换为一个JSON字符串

import org.apache.spark.sql.{DataFrame, Row, SparkSession}
import org.apache.spark.sql.functions._
import org.apache.spark.sql.types._

val spark = SparkSession.builder()
  .appName("DataFrame to JSON")
  .master("local")
  .getOrCreate()

val df1 = spark.createDataFrame(Seq(
  (1, "John"),
  (2, "Jane"),
  (3, "Alice")
)).toDF("id", "name")

val df2 = spark.createDataFrame(Seq(
  (1, "New York"),
  (2, "London"),
  (3, "Paris")
)).toDF("id", "city")

val value: Long = 1000

val combinedDF = df1.join(df2, Seq("id"))
  .withColumn("value", lit(value))

val jsonStr = combinedDF.toJSON.collect().mkString("[", ",", "]")