Scala Play Framework: cannot generate object from json with null values - scala

Question

I'm new to Scala and the Play Framework. I have written the following controller:
#Singleton
class MyController #Inject()(val controllerComponents: ControllerComponents) extends BaseController {
implicit val newMeasurementJson: OFormat[MeasurementModel] = Json.format[MeasurementModel]
def addMeasurement(): Action[AnyContent] = Action { implicit request =>
val content = request.body
val jsonObject: Option[JsValue] = content.asJson
val measurement: Option[MeasurementModel] =
jsonObject.flatMap(
Json.fromJson[MeasurementModel](_).asOpt
)
...
}
...
}
Where the endpoint receives the following JSON:
{
"sensor_id": "1029",
"sensor_type": "BME280",
"location": 503,
"lat": 48.12,
"lon": 11.488,
"timestamp": "2022-04-05T00:34:24",
"pressure": 94667.38,
"altitude": null,
"pressure_sealevel": null,
"temperature": 3.91,
"humidity": 65.85
}
MeasurementModel looks like this:
case class MeasurementModel(
sensor_id: String,
sensor_type: String,
location: Int,
lat: Float,
lon: Float,
timestamp: String,
pressure: Float,
altitude: Int,
pressure_sealevel: Int,
temperature: Float,
humidity: Float) {
}
Through testing I have seen that the null values in the JSON are causing the creation of the measurement object to be unsuccessful. How can I successfully handle null values and have them set in the generated MeasurementModel object?

Answer 1

The datatypes that can store null are Null and Option[].
Consider the following REPL code:
`
scala> val mightBeIntOrNull: Option[Int] = Option(1)
val a: Option[Int] = Some(1)
scala> val mightBeIntOrNull: Option[Int] = null
val a: Option[Int] = null
The Option wraps the Int value in Some, which can be extracted by pattern matching.
scala> val mightBeIntOrNull: Option[Int] = Option(1)
val mightBeIntOrNull: Option[Int] = Some(1)
scala> mightBeIntOrNull match {
| case Some(myIntVal) => println("This is an integer :" + myIntVal)
| case _ => println("This might be a null")
| }
This is an integer :1
scala> val mightBeIntOrNull: Option[Int] = null
val mightBeIntOrNull: Option[Int] = null
scala> mightBeIntOrNull match {
| case Some(myIntVal) => println("This is an integer :" + myIntVal)
| case _ => println("This might be a null")
| }
This might be a null
As Gaël J mentioned, you should add Option for the desired datatype in your case class
So the solution can be to wrap the datatype in option where you expect a null. Like:
{
"altitude": Option[Float],
"sensor_type": Option[String],
}