Scala：检查案例类树是否不包含任何null

Question

I use a Scala json serializer and just discovered that it doesn't set default values to case classes en deserialization, but instead set these missing values to null.

Fortunatly it didn't damage much my system until now mostly because of CRUD only fields being set to null, but in the future, I absolutely want to enforce that my JSON payloads do not have any null values.

My Json payloads are generally some kind of tree of case classes with lists and primitives. It is generally pretty simple, like a case class Person(addresses: List[Address], name: String, ...) with case class Address(street: String, number: Int) ...

---

• Is there a way to ensure that a case class has no null field in it?
• In case a null is found, is there a way to set it automatically to the default value instead of null?
• Would it work for nested case classes?

I guess there's something to do with the Product trait but don't really know where to start.

Answer 1

You can add a requirement on the case class so serialization will fail:

case class Person(  name: String, 
                    ssn: String,
                    homePhone: Option[Long],
                    cellPhone: Option[Long]){

  require(homePhone.isDefined || cellPhone.isDefined, "Person requires at least one phone number")
  require(ssn.length() == 9 && ssn.forall(Character.isDigit(_)), "ssn must be a String of 9 digits")
}

Answer 2

Can be this a solution?

def isCaseClassEmpty(product: Product): Boolean =
    product.productIterator.forall {
      case None => true
      case Some(x: Product) => isCaseClassEmpty(x)
      case _ => false
    }

case class Inner(b: Option[Int])
case class Root(a: Option[String]: inner: Option[Inner])

val root = Root(None, None))
isCaseClassEmpty(root) // true

val root = Root(None, Some(Inner(None)))
isCaseClassEmpty(root) // true

val root = Root(None, Some(Inner(Some(5))))
isCaseClassEmpty(root) // false

val root = Root(Some("test"), None)
isCaseClassEmpty(root) // false

Cheers :-)