update json string in scala using jackson

Question

I have a json

val nodeJson =
      s"""
       {
          "NAME":"node1",
          "CONFIG":{
          "colMap": {
              "idcols": [
                  
                 ],
                 "emailcols":[
                 ]
             },
             "col.partitions": "3"
          }
       }
       """
   

I have to populate "idcols" and "emailcols" array dynamically from scala array.

like if i have arrays:

val idcols = Array("per_id","dep_id")
val emailcols = Array("per_email","dep_email")

then these values need to set in the json string

I have to use com.fasterxml.jackson library.

I am able to get the arrays:

val obj = new ObjectMapper()
  val root = obj.readTree(nodeJson)
  val value = root.get("CONFIG").get("colMap")
  println(value)

But I am not sure how to update it and set it back to the json. Kinldy let me know how can i update the json string.

Answer 1

When using jackson you most mutators are not defined on JsonNode but rather the specific sub-classes for that type of node (in your case ArrayNode for json arrays)

For example to add a string to the idCols array you would:

root.get("CONFIG").get("colMap").get("idCols").asInstanceOf[ArrayNode].add("someArbitraryString")

If you prefer more type safety (at the performance cost of allocating an extra case class) you could also consider creating a case class matching the structure of your document, parsing the json into that, updating the scala case class and serializing back to a json string.