Joining two arrays in a json to one array in Nifi

Question

In Nifi, I have the following JSON:

{
  "list1":[1,2,3],
  "list2":[4,5]
}

I want the output to be:

{
 "Final_List":[1,2,3,4,5]
}

How should I do this?

Answer 1

You can add a JoltTransformJSON processor with a shift type transformation such as

[
  {
    "operation": "shift",
    "spec": {
      "*": {
        "*": {
          "@": "Final_List"
        }
      }
    }
  }
]

Edit for special case : If it was the case that those arrays have some common integer elements, then the above solution would yield repeating elements within the Final_List, but the following make that result having unique elements for this case too :

[
  {
    "operation": "shift",
    "spec": {
      "*": {
        "*": {
          "*": "Final_List.&"
        }
      }
    }
  },
  {
    "operation": "shift",
    "spec": {
      "Final_List": {
        "*": {
          "$": "&2"
        }
      }
    }
  },
  {
    "operation": "modify-overwrite-beta",
    "spec": {
      "*": "=toInteger(@(1,Final_List))"
    }
  }
]