Convert non-nullable to nullable in Kotlin - kotlin

Question

I have an Entity class as below:
#Entity(name = "Person")
#Table(name = "person")
class Person(
_firstName: String? = null,
_lastName: String?,
_address: String? = null)
) {
#Id
#GeneratedValue(strategy = GenerationType.AUTO, generator = "native")
#GenericGenerator(name = "native", strategy = "native")
var personId: Long? = null
var firstName = _firstName
var lastName = _lastName
var address = _address
}
The repository is as :
#Repository
interface PersonRepository : JpaRepository<Person?, Long?> {
fun findByIdAndFirstName (personId: Long, firstName: String): Person?
}
In my service class I am doing a findById(personId) and getting an Optional<Person?> in return.
While writing the testcases I am running into an issue with the Optional.
#Test
fun `test my changes`() {
every { personRepository.findById(PERSON_ID) } answers { Optional.of(getPerson())}
}
private fun getPerson(): Person {
return Person(_firstName = "First Name", _lastName = "Last Name", _address = "Address")
}
Since my getPerson() directly return the Person entity via a constructor the response is of type Person which is non-nullable.
But personRepository.findById(PERSON_ID) expects a nullable type Optional<Person?>.
Getting this as compilation error in my test class:
Type mismatch.
Required:
Optional<Person?>!
Found:
Optional<Person>
How can I fix this issue ?

Answer 1

You can cast it to nullable:
#Test
fun `test my changes`() {
every { personRepository.findById(PERSON_ID) } answers {
Optional.of(getPerson()) as Optional<Person?>
}
}
However (as Sweeper said in the comment) the type Optional<Person?> doesn't make much sense, and it looks like your JpaRepository should be parameterized on non-nullables. If it was, then findById would return Optional<Person> and you wouldn't have this issue.