Ignoring null fields when deserializing with Jackson - jackson

Question

I have the following Kotlin data class:
data class TestObject(
val boolField: Boolean,
val stringField: String,
val nullBoolField: Boolean = true,
val nullStringField: String = "default",
val notThereBoolField: Boolean = true,
val notThereStringField: String = "not there"
)
I am then attempting to deserialize some JSON into this class using Jackson v2.9.4 with the Jackson Kotlin plugin v2.9.4.1. The test JSON is as follows:
{
"boolField": true,
"stringField": "string",
"nullBoolField": null,
"nullStringField": null
}
The first two and the last two fields deserialize successfully - with the values from the JSON and the default values from the Kotlin data class, as appropriate. However, when the middle pair of fields are present, the deserialization fails with:
Instantiation of [simple type, class com.example.TestObject] value
failed for JSON property nullStringField due to missing (therefore
NULL) value for creator parameter nullStringField which is a
non-nullable type
I know I could solve the problem by changing the types of nullBoolField and nullStringField to Boolean? and String? respectively, but since default values are known I would rather not have to push the handling of null further down into the code by doing that.
The question is: is there any way of configuring Jackson to use the Kotlin data class default values for non-nullable properties when the property is present in the JSON but set to null?

Answer 1

You could try first to filter null values from json and after to deserialize it to Kotlin object.
Or you may to try add feature to kotlin-jackson module, with adding a new feature parameter, which will enable a null ignoring from json parameters and use default values.
You may do this by modify this line (if I'm not mistaken)

Answer 2

If you don't have any value and field is non-nullable then you should not pass it in request body:
{
"boolField": true,
"stringField": "string"
}
This results in following object, as expected:
{
"boolField": true,
"stringField": "string",
"nullBoolField": true,
"nullStringField": "default",
"notThereBoolField": true,
"notThereStringField": "not there"
}