How to extract data from stringified JSON field in Apache Spark SQL?

Apache Spark SQL lets us to manipulate JSON fields in many different ways. One of the features is a field extraction from a stringified JSON with json_tuple(json: Column, fields: String*) function:

    val contentString =
      """| { "value1": "1", "value2": "2" } """.stripMargin
    val sparkSession: SparkSession = SparkSession.builder()
      .appName("Spark SQL json_tuple")
    import sparkSession.implicits._

    val inputData = Seq((contentString)).toDF("json_field")

Let's ensure first that contentString is really a string by printing the schema (inputData.printSchema):

 |-- json_field: string (nullable = true)

To extract one of available keys of the stringified JSON, you can use this snippet:

    val extractedValues = inputData
      .withColumn("value1", functions.json_tuple($"json_field", "value1"))
      .withColumn("value2", functions.json_tuple($"json_field", "value2"))
      .map(row => (row.getAs[String]("value1"), row.getAs[String]("value2")))

    extractedValues should contain only (("1", "2"))