Modify json values from list of maps and save output - json

Question

I have the following example json that I read in using the play framework.
{
"field_a": "dummy",
"field_b": "dummy",
"nest": {
"nest_a": "dummy",
"nest_b": 87
},
"field_c": null,
"field_d": null,
"field_e": "chocolate",
"field_f": "sugar",
"array": [
"dummy entry"
],
"id": "Anything"
}
I Then have the following List of Maps that I want to swap out data with which is my Input:
val substitutionsList: List[mutable.Map[String, String]] = List(
mutable.Map("field_b" -> "dummy string", "field_d" -> "2016-01-01", "field_f" -> "2011-01-01"),
mutable.Map("field_b" -> "dummy string", "field_d" -> "2018-01-01", "field_f" -> "2018-01-01"),
mutable.Map("field_b" -> "dummy string", "field_d" -> "2018-04-01", "field_f" -> "2018-04-01"),
mutable.Map("field_b" -> "dummy string", "field_d" -> "2016-01-01", "field_f" -> "2016-01-01")
)
I am reading in the json as follows:
def parseSchemaJson(schemaContent: String) = Json.parse(schemaContent).as[JsObject]
val baseSchemaInput = parseSchemaJson(Source.fromFile("/dummy.json").mkString)
I want to iterate over my Input and swap out the values in the json for the values in my map and after each one is done, create a new .json file.
private def replaceField(json: JsObject, fieldToReplace: String): Option[String] = (json \ fieldToReplace).asOpt[String]
println(replaceField(baseSchemaInput, "field_a")) //prints dummy
I can list out the value in my json using something like this but I have no idea how to swap the value from my list into each respective bit and write out a json file.
First occurance of the expected output
{
"field_a": "dummy",
"field_b": "dummy string",
"nest": {
"nest_a": "dummy",
"nest_b": 87
},
"field_c": null,
"field_d": "2016-01-01",
"field_e": "chocolate",
"field_f": "2011-01-01",
"array": [
"dummy entry"
],
"id": "Anything"
}

Answer 1

Given the following substitution list:
val substitutionsList: List[mutable.Map[String, Any]] = List(
mutable.Map("field_b" -> "dummy string 1", "field_d" -> "2016-01-01", "field_f" -> "2011-01-01"),
mutable.Map("field_b" -> "dummy string 2", "nest" -> mutable.Map("nest_b" -> "90"))
)
Note that the second one updates a nested value. You need to create a nested Map to define nested values.
You can define a function to transform a Map[String, Any] (Any because we can have either a String or a Map as value) into a JsObject. This is a recursive function and will call itself in case the Value is a Map
def mapToJsObject(map: mutable.Map[String, Any]): JsObject =
JsObject(map.mapValues {
case v:String => JsString(v)
case v:mutable.Map[String, mutable.Map[String, Any]] => mapToJsObject(v.asInstanceOf[mutable.Map[String, Any]])
})
Then go through your list of substitutions and deep merge the JsObject made from each Map with the original JsObject using the deepMerge function defined on the JsObject class. It will merge the nested objects too. See API here
val substitutedJsObjects: List[JsObject] = substitutionsList
.map(mapToJsObject)
.map(baseSchemaInput.deepMerge)
This should give you a list of JsObjects, one per Map in your List
You can then write them to file. Here is an example to write one file per json string. Files will be named 0.json, 1.json, etc ..
def writeToFile(jsObject: JsObject, fileName: String): Unit = {
println("writing "+fileName)
val pw = new PrintWriter(new File(fileName))
pw.write(jsObject.toString())
pw.close()
}
substitutedJsObjects.zipWithIndex.foreach {
case (jsObject, index) => {
val fileName = index.toString + ".json"
writeToFile(jsObject, fileName)
}
}