JOLT Spec for DataFrame input (NiFi JoltTransformJson)

Question

Could you please help me writing JOLT spec for the following?

Input JSON:

{
  "a": "1",
  "b": "2",
  "c": "3",
  "d": "4"
}

I need to get output:

{
  "columns": ["a","b","c","d"],
  "data": [[1,2,3,4]]
}

Answer 1

You can use the shift transformation below :

[
  {
    "operation": "shift",
    "spec": {
      "*": {
        "$": "columns",
        "@": "data[0]"
      }
    }
  }
]

If the elements of the data array must strictly be of type integer, then a modify-overwrite-beta transformation needed too, such as

[
  {
    "operation": "modify-overwrite-beta",
    "spec": {
      "*": "=toInteger"
    }
  },
  {
    "operation": "shift",
    "spec": {
      "*": {
        "$": "columns",
        "@": "data[0]"
      }
    }
  }
]