值键不是play.api.libs.json.JsValue的成员

Question

I'm try to get the head from the keys of JsValue type in Scala. I googled a lot to know how to get the head key from JsValue type.

Finally, I found that result.keys.head is the way to get the head key, but it throws error value keys is not a member of play.api.libs.json.JsValue .

And my result variable has the below form of data:

{
    "intents": [{
        "intent": "feeling",
        "confidence": 0.1018563217175903
    }],
    "entities": [],
    "input": {
        "text": "{reset-encounter}"
    },
    "output": "Good"
}

Code:

import play.api.libs.json._
val jsonStr = """
{
        "intents": [{
            "intent": "feeling",
            "confidence": 0.1018563217175903
        }],
        "entities": [],
        "input": {
            "text": "{reset-encounter}"
        },
        "output": "Good"
    }
"""
val result = Json.parse(jsonStr)
println("key: ", result.keys.head)

At result.keys.head line, throws error.

I'm not sure but I think, may be I'm doing something wrong here.

Answer 1

What are you trying to get? That's not the way to deal with play.api.Json objects.

.keys would result in a Map , not in a JsValue.

Check the documentation: https://www.playframework.com/documentation/2.5.x/ScalaJson

If you want to access a specific key ( https://www.playframework.com/documentation/2.5.x/ScalaJson#Traversing-a-JsValue-structure ) you should try:

result \ "keyName"

or for a recursive search:

result \\ "keyName"

Answer 2

Json.parse produces a JsValue , which could represent any type of json object (boolean, number, array, etc). If you know you're working with an object, you can use .as[JsObject] :

import play.api.libs.json._

val result = Json.parse(jsonStr).as[JsObject]
println("key: " + result.keys.head)