How can I convert a json string to a scala map?

问题:

I have a nested json whose structure is not defined. It can be different each time I run since I am reading from a remote file. I need to convert this json into a map of type Map[String, Any]. I tried to look into json4s and jackson parsers but they don't seem to solve this issue I have. Does anyone know how I can achieve this?

Example string:

{"body":{
    "method":"string",
    "events":"string",
    "clients":"string",
    "parameter":"string",
    "channel":"string",
    "metadata":{
        "meta1":"string",
        "meta2":"string",
        "meta3":"string"
    }
},
"timestamp":"string"}

The level of nesting can be arbitrary and not predefined.
To help with the use case:
I have a Map[String,Any] which I need to store in a file as backup. So I convert it to a json string and store it in a file. Now everytime I get new data, I need to get the json from the file, convert it to a map again and perform some computation. I cannot store the map in memory since I would lose that if my job fails.
I need a solution that would convert the json string back to the original map I had before i converted it.

回答1:

I tried the following method with json4s 3.2.11 and it works:

import org.json4s._
import org.json4s.jackson.JsonMethods._

//...
def jsonStrToMap(jsonStr: String): Map[String, Any] = {
  implicit val formats = org.json4s.DefaultFormats

  parse(jsonStr).extract[Map[String, Any]]
}

Maybe you didn't define the implicit val of type Formats? Note also that you don't need to have an implicit val within every and each method as long as it's findable in the scope.

回答2:

You can use the following code to parse a JSON string into a Map[String, Any]

val jsonMap = parse(jsonString).values.asInstanceOf[Map[String, Any]]

However, this is not typesafe and hence should be used with caution when extracting values from the map.