Transform JSON using Scala

Question

I have the following JSON

{
    "record1": {
        "firstName": "John",
        "lastName": "Doe",
        "locations": {
            "29b2f2295cd74b8cbb53db4379f0d823": "New York"
        }
    },
    "record2": {
        "firstName": "Carol",
        "lastName": "Rees",
        "locations": {
            "0055bb74b4984156b821ebbea6937084": "California"
        }
    },
    "record3": {
        "firstName": "Colin",
        "lastName": "Scott",
        "locations": {
            "aba67f566fc24f8a8eb3165648ca5e4f": "Toronto",
            "b847750c565246638dbc72cb89ead227": "London"
        }
    }
}

which needs to be transformed to the following using Scala

{
    "record1": {
        "firstName": "John",
        "lastName": "Doe",
        "locations": [{
            "id" : "29b2f2295cd74b8cbb53db4379f0d823",
            "location": "New York"
        }]
    },
    "record2": {
        "firstName": "Carol",
        "lastName": "Rees",
        "locations": [{
            "id" : "0055bb74b4984156b821ebbea6937084",
            "location": "California"
        }]
    },
    "record3": {
        "firstName": "Colin",
        "lastName": "Scott",
        "locations": [{
            "id": "aba67f566fc24f8a8eb3165648ca5e4f",
            "location:" : "Toronto"
        },
            {
            "id" : "b847750c565246638dbc72cb89ead227",
            "location": "London"
        }]
    }
}

I am being new to scala, this is what I have so far

case class PersonEntry(firstName: String, lastName: String, locations: Map[String, String])

val jsonMapper = JsonMapper.builder().addModule(DefaultScalaModule).build()

val inputJson: String = "{\n    \"record1\": {\n        \"firstName\": \"John\",\n        \"lastName\": \"Doe\",\n        \"locations\": {\n            \"29b2f2295cd74b8cbb53db4379f0d823\": \"New York\"\n        }\n    },\n    \"record2\": {\n        \"firstName\": \"Carol\",\n        \"lastName\": \"Rees\",\n        \"locations\": {\n            \"0055bb74b4984156b821ebbea6937084\": \"California\"\n        }\n    },\n    \"record3\": {\n        \"firstName\": \"Colin\",\n        \"lastName\": \"Scott\",\n        \"locations\": {\n            \"aba67f566fc24f8a8eb3165648ca5e4f\": \"Toronto\",\n            \"b847750c565246638dbc72cb89ead227\": \"London\"\n        }\n    }\n}"
val parsedPerson = jsonMapper.readValue(inputJson, classOf[Map[String, Any]])
val personMap: Map[String, PersonEntry] = parsedPerson.mapValues(jsonMapper.convertValue(_, classOf[PersonEntry]))

What JSON library are you using? Look's like Jackson, right? — Gaël J
– Gaël J, Commented Dec 30, 2022 at 17:31

Gaël J · Accepted Answer · 2022-12-30 17:43:07Z

There are several ways to do it. As you already have written a case class representing the input data, I would:

create a case class representing the output data
parse input as input case classes
map input case class to output case class
generate JSON for output case classes

If performance matters, you could look to work without parsing to case classes and operate directly on the JSON input but I won't explain this option.

That is, something along the lines of:

case class PersonOutput(firstName: String, lastName: String, locations: Seq[Location])

case class Location(id: String, location: String)

val output: Map[String, PersonOutput] = jsonMapper
  .readValue(inputJson, classOf[Map[String, PersonEntry]])
  .map { case (key, person) => 
    val newLocations = person.locations.map { 
      case (k, v) => Location(k, v)
    }
    key -> PersonOutput(person.firstName, person.lastName, newLocations)
  }

// Then generate JSON for output

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