scala iterate over JSON Array

Question

I have a very simple JSON as below and I want to get sJson[0], sJson[1] objects, How can I achieve this ?

scala> val jsonA = "[{'foo': 4, 'bar': 'baz'},{'bla': 4, 'bar': 'bla'}]"
jsonA: String = [{'foo': 4, 'bar': 'baz'},{'bla': 4, 'bar': 'bla'}]

scala> val sJson = parseFull(jsonA)
sJson: Option[Any] = None

scala> println(sJson.toString())
None

Yup, scala.util.parsing.j‌son.JSON package. I just want that sJson 's obj[0], obj[1] .. etc — Swapnil Kotwal
– Swapnil Kotwal, Commented Aug 17, 2016 at 11:23

Samar · Accepted Answer · 2016-08-17 11:54:13Z

2

JSON notation wants you to surround variables with double quotes:

val jsonA = """[{"foo": 4, "bar": "baz"},{"bla": 4, "bar": "bla"}]"""
val sJson = parseFull(jsonA).get.asInstanceOf[List[Map[String,String]]] // List(Map(foo -> 4.0, bar -> baz), Map(bla -> 4.0, bar -> bla))

edited Aug 17, 2016 at 11:54

answered Aug 17, 2016 at 10:49

Samar

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7 Comments

Swapnil Kotwal Over a year ago

Get some exceptions

scala> val sJson = parseFull(jsonA).get java.util.NoSuchElementException: None.get   at scala.None$.get(Option.scala:347)   at scala.None$.get(Option.scala:345)

Samar Over a year ago

hmm, what is your jsonA? the one I posted in the answer is parsing fine.

Samar Over a year ago

I see single quotes around the variables in your JSON in the image you just posted.

Swapnil Kotwal Over a year ago

lol. Single quotes was the problem. Thanks Samar. It's working !

Swapnil Kotwal Over a year ago

Samar, could you please do one more favour for me, my real quetion was to get first object from the JSON or list. I'm getting scala> sJson(0) <console>:23: error: Any does not take parameters sJson(0) error. :(

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faizan · Accepted Answer · 2016-08-17 12:00:09Z

While the scala.util.parsing.j‌son.JSON works well it is best to use an external library like json4s which has a fluent scala api.

You can query json just like you query xml (like JsonPath).

Below are the steps how you can use json4s for your need once you have it in your project.

First add the following imports

import org.json4s._
import org.json4s.native.JsonMethods._

Now create a Jvalue by doing

val jsonA = """[{"foo": 4, "bar": "baz"},{"bla": 4, "bar": "bla"}]"""
val json = parse(jsonA)

Your json object is as

json: org.json4s.JValue = JArray(List(JObject(List((foo,JInt(4)), (bar,JString(baz)))), JObject(List((bla,JInt(4)), (bar,JString(bla))))))

To get the first (0th) child

val firstChild = (json)(0)

firstChild: org.json4s.JsonAST.JValue = JObject(List((foo,JInt(4)), (bar,JString(baz))))

To get a string representation of this firstChild

val firstChildString = compact(render(firstChild))

firstChildString: String = {"foo":4,"bar":"baz"}

See the section Querying JSON in json4s home page for more.

Note: to import the jars you can use maven/gradle or import them into scala repl by using :require command.

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