Determine whether or not an array has element, Nifi

Question

I have the following json:

{
  "a":[1,2,3,4],
  "b":[]
}

I want to know whether or not the array has elements or not. Thus the desired output required is:

{
  "a":[1,2,3,4],
  "b":[],
  "is_element_in_a":True,
  "is_element_in_b":False    
}

What will be the jolt spec expression for this?

Answer 1

You can use modify-overwrite-beta transformation spec along with size function in order to determine the size of the list is whether zero or not in the first step, and then use a shift transformation spec to print the boolean values within a conditional logic such as

[
  {
    "operation": "modify-overwrite-beta",
    "spec": {
      "in_a": "=size(@(1,a))",
      "in_b": "=size(@(1,b))"
    }
  },
  {
    "operation": "shift",
    "spec": {
      "*": "&",
      "in_*": {
        "0": {
          "#False": "is_element_&2"
        },
        "*": {
          "#True": "is_element_&2"
        }
      }
    }
  }
]