spark_jdbc_read_write.scala

val jdbcDF = spark.read.format("jdbc").options( 
  Map(
  "driver" -> "org.postgresql.Driver",
  "url" -> "jdbc:postgresql://localhost/?user=postgres&password=postgres",
  "dbtable" -> "nifi_test"
  )
).load()
  
jdbcDF.show

case class Test (field1: String, field2: String)
val test = List(Test("B", "xx"), Test("B", "2"), Test("B", "35"), Test("A", "6"), Test("A", "3"))
val rdd = sc.parallelize(test)
val df = rdd.toDF

df.write.format("jdbc").options( 
  Map(
  "driver" -> "org.postgresql.Driver",
  "url" -> "jdbc:postgresql://localhost/?user=postgres&password=postgres",
  "dbtable" -> "nifi_test"
  )
).mode("append").save("nifi_test")