Scala 2.10: Array + JSON arrays to hashmap

Question

After reading a JSON result from a web service response:

val jsonResult: JsValue = Json.parse(response.body)

Containing content something like:

{
    result:  [
    ["Name 1", "Row1 Val1", "Row1 Val2"],
    ["Name 2", "Row2 Val1", "Row2 Val2"]
             ]
 }

How can I efficiently map the contents of the result array in the JSON with a list (or something similar) like:

val keys = List("Name", "Val1", "Val2")

To get an array of hashmaps?

You should be more explicit about the relationship between the input (the nested List[List[String]] and the output (List[String]) ... or is the output an "array of [hash]maps"?. And if the sequence of map is in fact the desired final result, it's even less clear how it relates to your input. — Randall Schulz
– Randall Schulz, Commented Jan 15, 2013 at 1:56
I'm looking for a result that is something like: List(Map("Name" -> "Name 1", "Val1" -> "Row1 Val1", "Val2" -> "Row1 Val2"), Map("Name" -> "Name 2", "Val1" -> "Row2 Val1", "Val2" -> "Row2 Val2")) — George Hernando
– George Hernando, Commented Jan 15, 2013 at 3:11
I'm sorry, but you're really not making your assumptions clear. Please try to specify exactly how the result / output relates to the input. I sense that there is some sort of string manipulation in play, but I can't be sure. I don't mean to be tedious, but this is what programming is about. Being entirely clear and unambiguous about how the output of your program relates to its input. — Randall Schulz
– Randall Schulz, Commented Jan 15, 2013 at 5:49

Bruno Grieder · Accepted Answer · 2013-01-15 17:39:39Z

2

Something like this ? This solution is functional and handles None/Failure cases "properly" (by returning a None)

val j = JSON.parseFull( json ).asInstanceOf[ Option[ Map[ String, List[ List[ String ] ] ] ] ]

val res = j.map { m ⇒
    val r = m get "result"
    r.map { ll ⇒
        ll.foldRight( List(): List[ Map[ String, String ] ] ) { ( l, acc ) ⇒
            Map( ( "Name" -> l( 0 ) ), ( "Val1" -> l( 1 ) ), ( "Val2" -> l( 2 ) ) ) :: acc
        }
    }.getOrElse(None) 
}.getOrElse(None)

Note 1: I had to put double quotes around result in the JSON String to get the JSON parser to work
Note 2: the code could look nicer using more "monadic" sugar such as for comprehensions or using applicative functors

edited Jan 15, 2013 at 17:39

answered Jan 15, 2013 at 15:25

Bruno Grieder

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