Convert a JsArray of JsArray into into Case class

Question

My question is a kind-of extension to this and this one too.

My JSON looks like:

{
    "id": "id1",
    "results": [
        {
            "exceed_size": "yes",
            "rows_count": 1001,
            "runtime_seconds": 0.02199999988079071,
            "columns": [
                "COL_1",
                "COL_2",
                "COL_3",
                "COL_4",
                "COL_5",
                "COL_6",
                "COL_7",
                "COL_8",
                "COL_9"
            ],
            "columns_type": [
                "number",
                "string",
                "string",
                "string",
                "number",
                "time",
                "time",
                "number",
                "string"
            ],
            "limit": 1000,
            "index": 0,
            "rows": [
                [
                    "9",
                    " C68894",
                    "                                                                                                    ",
                    "",
                    "0",
                    "2018-05-02 03:13:00.0",
                    "2017-12-02 22:32:00.0",
                    "",
                    "Approved  "
                ],
                [
                    "65",
                    "325806   ",
                    "msm                                                                             ",
                    "                 ",
                    "2",
                    "2018-05-02 03:13:00.0",
                    "2018-07-06 06:00:00.0",
                    "13",
                    "Approved  "
                ],
                ...
            ]
        },
        ...
    ]
}

I'm using Play Framework provided JSON Library for JSON Parsing.

If you have a look at the rows value, it is a JsArray of a JsArray of string values. I have been trying to convert rows into a List of objects of a case class, where my case class would look like:

case class Rows(col_1: String, col_2: String, ... , col_9: String)

I had tried to do something like:

val rows = (response \\ "rows").head.as[List[List[(String, String, ... , String)]]].flatten

Trying This way threw an error, which I was sure of won't work. How do I convert such a JsArray into a List of objects of a case class?

EDIT 1:

As @MilanRegmi suggested, I tried:

implicit val jsonFormat: Format[Rows] = Json.format[Rows]

val emails = (response \ "results" \ "rows").as[JsArray]
            .value.map(j => j.validate[Rows].get)

Trying this resulted in:

Exception in thread "main" play.api.libs.json.JsResultException: JsResultException(errors:List((,List(JsonValidationError(List([{"exceed_size":"yes","rows_count":1001,"runtime_seconds":0.01600000075995922,"columns":["COL_1","COL_2","COL_3","COL_4","COL_5","COL_6","COL_7","COL_8","COL_9"],"columns_type":["number","string","string","string","number","time","time","number","string"],"limit":1000,"index":0,"rows":[["9"," C68894","","","0","2018-05-02 03:13:00.0","2017-12-02 22:32:00.0","","Approved  "],["65","325806   ","msm                                                                             ","                 ","2","2018-05-02 03:13:00.0","2018-07-06 06:00:00.0","13","Approved  "],...]}] is not an object),WrappedArray())))))
    at play.api.libs.json.JsReadable$$anonfun$2.apply(JsReadable.scala:25)
    at play.api.libs.json.JsReadable$$anonfun$2.apply(JsReadable.scala:25)
    at play.api.libs.json.JsError.fold(JsResult.scala:64)
    at play.api.libs.json.JsReadable$class.as(JsReadable.scala:23)
    at play.api.libs.json.JsUndefined.as(JsLookup.scala:181)
    at com.cmdwldap.restapi.User.getEntitlementUserData(User.scala:150)
    at com.cmdwldap.restapi.User$.main(User.scala:168)
    at com.cmdwldap.restapi.User.main(User.scala)

PS: Line 150 corresponds to the place where val emails is mentioned.

Are you looking for something like this? (Json.parse(jsonString) \ "results" \ 0 \ "rows").validate[List[List[String]]] — Tomer Shetah
– Tomer Shetah, Commented Feb 22, 2021 at 13:46

MilanRegmi · Accepted Answer · 2019-08-16 17:17:45Z

1

Try this:

val rows: Seq[Rows] = (json \ "result" \ "rows").as[JsArray].value.map(j => j.validate[Rows].get)

Update:

After going through your question for several times. I got your question now. You want to convert List[List[String] into CaseClass.

First, you cannot convert Array of List of String into a case class directly. So, you need to convert Array[String] to JsObject where key should be fieldName of the class. After that we can fetch fieldName using reflection. Then, we need to create JsObject to match caseClass and List[String] using the fieldName.

Pro-grammatically, above explained scenario can be solve in the following way:

 case class Rows(col1: Option[String] = None,
               col2: Option[String] = None,
               col3: Option[String] = None,
               col4: Option[String] = None,
               col5: Option[String] = None,
               col6: Option[String] = None,
               col7: Option[String] = None,
               col8: Option[String] = None,
               col9: Option[String] = None)

implicit val reads = Json.reads[Rows]

This is our case class and the implicits reads. Now, the above explained part is below:

import scala.reflect.runtime.universe._

def classAccessors[T: TypeTag]: List[MethodSymbol] = typeOf[T].members.collect {
    case m: MethodSymbol if m.isCaseAccessor => m
  }.toList


 val rowFieldNames = classAccessors[Rows].map(k => k.name.toString)
 val results =  (json \ "results").as[JsArray].value.flatMap{
    r => (r \ "rows").as[JsArray].value
  }.map{row =>
    val rowArray = row.as[JsArray]
    val rowArraySeq = rowArray.value.map(_.as[JsString]).map(_.value)
    val map = rowArraySeq.foldLeft(Map.empty[String, JsValue]){
      (r, c) =>
        val indexOfCurrentValue = rowArraySeq.indexOf(c)
        val fieldName = rowFieldNames(indexOfCurrentValue)
        r.+((fieldName, JsString(c)))
    }
    val rowJsObject = JsObject(map)
    Json.toJson(rowJsObject)
        }.toList

edited Aug 16, 2019 at 17:17

answered Aug 16, 2019 at 2:46

MilanRegmi

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13 Comments

Sparker0i Over a year ago

Error: No implicits found for parameter rds: Reads[Rows]

MilanRegmi Over a year ago

You have missed implicits reads and writes. Add implicit formatter like this: implicit val jsonFormat: Format[Rows] = Json.format[Rows]

Sparker0i Over a year ago

Please check EDIT 1

MilanRegmi Over a year ago

It seems like you have provided an invalid json. Please check your json first and make sure it is valid json.

Sparker0i Over a year ago

It is a valid JSON.. :(

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