I have a JSON body in the following form:
val body =
{
"a": "hello",
"b": "goodbye"
}
I want to extract the VALUE of "a" (so I want "hello") and store that in a val. I know I should use "parse" and "Extract" (eg. val parsedjson = parse(body).extract[String]) but I don't know how to use them to specifically extract the value of "a"
To use extract you need to create a class that matches the shape of the JSON that you are parsing. Here is an example using your input data:
val body ="""
{
"a": "hello",
"b": "goodbye"
}
"""
case class Body(a: String, b: String)
import org.json4s._
import org.json4s.jackson.JsonMethods._
implicit val formats = DefaultFormats
val b = Extraction.extract[Body](parse(body))
println(b.a) // hello
You'd have to use pattern matching/extractors:
val aOpt: List[String] = for {
JObject(map) <- parse(body)
JField("a", JString(value)) <- map
} yield value
alternatively use querying DSL
parse(body) \ "a" match {
case JString(value) => Some(value)
case _ => None
}
These are options as you have no guarantee that arbitrary JSON would contain field "a".
See documentation
extract would make sense if you were extracting whole JObject into a case class.
.get("a")