CODEWITHSUNDEEP
jsonlistscalaparsinggson
Electric Coffee
Electric Coffee

Reputation: 12144

"Failed to invoke public scala.collection.immutable.List() with no args" using GSON

First off here's my code:

// Description.scala
package com.wausoft.jsonrpc.model

import com.google.gson.annotations.SerializedName

class Description {
  @SerializedName("Language")
  var language = ""

  @SerializedName("Description")
  var description = ""
}

// Item.scala
package com.wausoft.jsonrpc.model

import com.google.gson.annotations.SerializedName

class Item {
  @SerializedName("Number")
  var number = 0

  @SerializedName("Description")
  var description: List[Description] = Nil
}

// Result.scala
package com.wausoft.jsonrpc.model

import com.google.gson.annotations.SerializedName

class Result {
  @SerializedName("Type")
  var typeNum = 0

  @SerializedName("Description")
  var description: List[Description] = Nil

  @SerializedName("Items")
  var items: List[Item] = Nil
}

// Response.scala
package com.wausoft.jsonrpc.model

class Response {
  var jsonRPC = ""
  var result: List[Result] = Nil
  var id = 0
}

// main file
package com.wausoft.jsonrpc

import scala.io.Source
import com.wausoft.jsonrpc.model._
import com.google.gson._


object Program {
    def getJson(file: String): String = Source.fromFile(file)("UTF-8").mkString

    def parseJFile(json: String): Response = new Gson().fromJson(json, classOf[Response])

    // insert main method here 
}

I get the error in the title when I try to parse the data to a POSO, it works fine if I replace all of the lists with arrays, but the thing that bothers me is that this works:

var lst: List[Int] = Nil
lst = List(1,2,3,4,5)

lst foreach print // produces 12345

If the above example works, why doesn't my code? I mean I'm basically doing the exact same, with the only exception that I let Gson handle the list making, is it because it's wrapped in a class, or did I miss something?

Upvotes: 4

Views: 3993

Answers (1)

Dave Swartz
Dave Swartz

Reputation: 910

See How can I use Gson in Scala to serialize a List?.

Quote from the question: "Gson doesn't know about Scala's collection classes". This answer shows how to serialize a class with a Scala List member to JSON using GSON. The former is the source of the problem, the later is the solution.

Upvotes: 2

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