How can I set a field to be kept as plain while Finatra is parsing a request into a case class?

Question

I have a controller handling a route like 'POST /doit', the json body is automatically parsed into a case class using Finatra built in tools (Jackson, etc), something like this:

class MyController extends Controller {
  post("/doit") { request: MyRequest =>
    // something
  }
}

case class MyRequest(
  id: String,
  custom: String
)

Here are some valid requests:

{ "id": "my id", "custom": "my custom" }

{ "id": "my id", "custom": "{'x': 'y'}" }

As you can see, 'custom' field can be a JSON which can't be deserialized because Jackson expect it to be a POJO instead of a String, I tried wrapping this JSON with quotes but they are ignored and the field is handled as JSON.

How can I let Jackson library to know that this field should be kept plain?

I had read and the best solution I came up with is to write a custom deserializer, in this case, I have not idea how to integrate with Finatra.

Answer 1

As "Ryan O'Neill" pointed out in Finatra Google Group, there are examples for writing a custom deserializer in ExampleCaseClasses.scala.

I'm copying the following code from previous scala source:

import com.fasterxml.jackson.databind.annotation.JsonDeserialize

case class CaseClassWithCustomDecimalFormat(
  @JsonDeserialize(using = classOf[MyBigDecimalDeserializer])
  myBigDecimal: BigDecimal,
  @JsonDeserialize(using = classOf[MyBigDecimalDeserializer])
optMyBigDecimal: Option[BigDecimal])

class MyBigDecimalDeserializer extends JsonDeserializer[BigDecimal] {
  override def deserialize(jp: JsonParser, ctxt: DeserializationContext): BigDecimal = {
    val jsonNode: ValueNode = jp.getCodec.readTree(jp)
    BigDecimal(jsonNode.asText).setScale(2, RoundingMode.HALF_UP)
  }

  override def getEmptyValue: BigDecimal = BigDecimal(0)
}

Thanks Ryan.