SCALA: Reading JSON file with the path provided - scala

Question

I have scenario where I will be getting different JSON result from multiple API's, I need to read specific value from the response.
For instance my JSON response is as below, now I need a format from user to provider by which I can read the value of Lat, Don't want hard-coded approach for this, user can provided a node to read in some other json file or txt file:
{
"name" : "Watership Down",
"location" : {
"lat" : 51.235685,
"long" : -1.309197
},
"residents" : [ {
"name" : "Fiver",
"age" : 4,
"role" : null
}, {
"name" : "Bigwig",
"age" : 6,
"role" : "Owsla"
} ]
}

Answer 1

You can get the key of json using scala JSON parser as below. Im defining a function to get the lat, which you can make generic as per your need, so that you just need to change the function.
import scala.util.parsing.json.JSON
val json =
"""
|{
| "name" : "Watership Down",
| "location" : {
| "lat" : 51.235685,
| "long" : -1.309197
| },
| "residents" : [ {
| "name" : "Fiver",
| "age" : 4,
| "role" : null
| }, {
| "name" : "Bigwig",
| "age" : 6,
| "role" : "Owsla"
| } ]
|}
""".stripMargin
val jsonObject = JSON.parseFull(json).get.asInstanceOf[Map[String, Any]]
val latLambda : (Map[String, Any] => Option[Double] ) = _.get("location")
.map(_.asInstanceOf[Map[String, Any]]("lat").toString.toDouble)
assert(latLambda(jsonObject) == Some(51.235685))
The expanded version of function,
val latitudeLambda = new Function[Map[String, Any], Double]{
override def apply(input: Map[String, Any]): Double = {
input("location").asInstanceOf[Map[String, Any]]("lat").toString.toDouble
}
}
Make the function generic so that once you know what key you want from the JSON, just change the function and apply the JSON.
Hope it helps. But there are nicer APIs out there like Play JSON lib. You simply can use,
import play.api.libs.json._
val jsonVal = Json.parse(json)
val lat = (jsonVal \ "location" \ "lat").get