How to read a JSON file into a Map, using Scala

Question

How can I read a JSON file into a Map, using Scala. I've been trying to accomplish this but the JSON I am reading is nested JSon and I have not found a way to easily extract the JSON into keys because of that. Scala seems to be wanting to also convert the nested JSON String into an object. Instead, I want the nested JSON as a String "value". I am hoping someone can clarify or give me a hint on how I might do this.

My JSON source might look something like this:

{
  "authKey": "34534645645653455454363",
  "member": {
    "memberId": "whatever",
    "firstName": "Jon",
    "lastName": "Doe",
    "address": {
      "line1": "Whatever Rd",
      "city": "White Salmon",
      "state": "WA",
      "zip": "98672"
    },
    "anotherProp": "wahtever",
  }
}

I want to extract this JSON into a Map of 2 keys without drilling into the nested JSON. Is this possible? Once I have the Map, my intention is to add the key-values to my POST request headers, like so:

val sentHeaders = Map("Content-Type" -> "application/javascript", 
   "Accept" -> "text/html", "authKey" -> extractedValue,
   "member" -> theMemberInfoAsStringJson)
http("Custom headers")
.post("myUrl")
.headers(sentHeaders)

Yes, first level keys only. So, i would want 1st level values as String, not as json/object. — djangofan

Antot Antot · Accepted Answer · 2018-09-26T07:08:19

Since the question is tagged 'gatling', behind the curtains this lib depends on Jackson/fasterxml for JSON processing, so we can make use of it.

There is no way to retrieve a nested structured part of JSON as String directly, but with very few additional code the result can still be achieved.

So, having the input JSON:

val json = """{
             |  "authKey": "34534645645653455454363",
             |  "member": {
             |    "memberId": "whatever",
             |    "firstName": "Jon",
             |    "lastName": "Doe",
             |    "address": {
             |      "line1": "Whatever Rd",
             |      "city": "White Salmon",
             |      "state": "WA",
             |      "zip": "98672"
             |    },
             |    "anotherProp": "wahtever"
             |  }
             |}""".stripMargin

A Jackson's ObjectMapper can be created and configured for use in Scala:

// import com.fasterxml.jackson.module.scala.DefaultScalaModule

val mapper = new ObjectMapper().registerModule(DefaultScalaModule)

To parse the input json easily, a dedicated case class is useful:

case class SrcJson(authKey: String, member: Any) {
  val memberAsString = mapper.writeValueAsString(member)
}

We also include val memberAsString in it, which will contain our target JSON string, obtained through a reverse conversion from initially parsed member which actually is a Map.

Now, to parse the input json:

val parsed = mapper.readValue(json, classOf[SrcJson])

The references parsed.authKey and parsed.memberAsString will contain the researched values.

How to read a JSON file into a Map, using Scala

2 Answers